MSA 5th Edition Gas Detection Handbook

M S A G a s D e t e c t i o n H a n d b o o k The MSA Gas Detection Handbook is designed to introduce users to key terms and concepts in gas detection and to serve as a quick reference manual for information such as speciﬁc gas properties, exposure limits and other data. The Handbook contains: • a glossary of essential gas detection terms and abbreviations. • a summary of key principles in combustible and toxic gas monitoring. • reference data—including physical properties and exposure limits— for the most commonly monitored gases, in industrial and various other environments. • a comparison of the most widely-used gas detection technologies. • a table indicating the gas hazards common to speciﬁc applications within major industries. • a summary of key gas detection instrumentation approvals information, including hazardous locations classiﬁcation. • MSA’s exclusive Sensor Placement Guide, detailing important factors to take into consideration when determining optimum gas sensor placement. Note to User: Mine Safety Appliances Company (“MSA”) makes no warranties, understandings or representations, whether expressed, implied or statutory regarding this gas detection handbook. MSA specifically disclaims any warranty for merchantability or fitness for a particular purpose. In no event shall MSA, or anyone else who has been involved in the creation, production or delivery of this handbook be liable for any direct, indirect, special, incidental or consequential damages arising out of the use of or inability to use this handbook or for any claim by any other party. M S A G a s D e t e c t i o n H a n d b o o k Table of Contents Section 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Gas Detection Terms & Abbreviations Section 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 Gas Monitoring Categories Combustible Atmospheres Toxic Atmospheres Oxygen Deﬁciency/ Enrichment Atmospheres Gas Detection Technologies Gas Sampling Section 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 Gas Information Table Section 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71 A Selection of Gases Typically Associated with Various Industries Section 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 Approvals Hazardous Locations Classiﬁcation CLASS I: Flammable Gases, Vapors or Liquids CLASS II: Combustible Dusts CLASS III: Ignitable Fibers & Flyings ATEX Explosive Atmospheres A Selection of Recognized Testing Laboratories System Installation Section 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 Sensor Placement Guide Section 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 Calibration Section 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142 Resources Section 1 Gas Detection Terms & Abbreviations M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Terms & Abbreviations ACGIH - American Conference of Governmental Industrial Hygienists. Alarm Set Point - The selected gas concentration level at which an alarm is activated. Ambient air - Surrounding air to which the sensing element is normally exposed in its installed position. Asphyxiant - A substance that impairs normal breathing by displacing oxygen. Atmosphere - The total gases, vapors, mists and fumes present in a speciﬁc location. Autoignition Temperature [also “spontaneous ignition temperature” (SIT) - The minimum temperature at which a combustible substance (gas, vapor, liquid or solid) will ignite and sustain combustion under its own heat energy. Bump Check (Functional Test) - Procedure used to verify the response of an instrument which does not include actual adjustment. (also known as “Span Check”) Calibration - Procedure by which the performance of a detector is veriﬁed to maximize the accuracy of its readings. A calibration is performed by: (1) comparing the instrument with a known standard, and (2) adjusting the instrument reading to match the standard. Calibration Gas (also “Span Gas”) - A known concentration of gas that is used to set instrument accuracy. Ceiling - The maximum gas concentration to which a worker may be exposed. Combustible Gas* - A gas that is capable of igniting and burning. Combustion - The rapid oxidation of a substance involving heat and light. Confined Space - An area that is large enough for an employee to bodily enter and perform work, has limited or restricted areas of entry or exit, and is not designed for continuous human occupancy. * Any material that will burn at any temperature is considered to be “combustible”, so this term covers all such materials, regardless of how easily they ignite. The term “flammable” specifically refers to those combustible gases that ignite easily and burn rapidly. 8 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Terms & Abbreviations Controller - The part of a gas detector that provides centralized processing of the gas signal. The controller receives and responds to the electrical signal from the sensor to output an indication, alarm or other function. Cross Sensitivity - The predictable response of a detector to compounds other than the target gas. Dew Point - The temperature at which a gas (air) is saturated with a condensable component. Diffusion - Process by which particles spread from regions of higher concentration to regions of lesser concentration as a result of random molecular movement. Also used to describe the process by which the atmosphere being monitored is transported to the gas-sensing element by natural random molecular movement. Electrochemical Sensor - A sensor that uses an electrochemical reaction to provide an electrical output proportional to the measured gas concentration. Explosion - Rapid uncontrolled combustion process which generates a high temperature, a large volume of gas, and a pressure or shock wave. Explosionproof (XP) - Method of protection in which an explosion in a hazardous location is prevented by containing any combustion within the device, and thereby, preventing it from spreading into the atmosphere surrounding the enclosure. Explosive (or “Flammable”) Limits - Though a ﬂammable liquid can support combustion at its ﬂash point temperature, to sustain it requires the vapor concentration to be between two speciﬁc levels, or “ﬂammable limits”, the lower ﬂammable limit and the upper ﬂammable limit. (see below) Any gas or vapor concentration that falls between these two limits is in the ﬂammable range. • Lower Explosive (or “Flammable”) Limit (LEL) - the minimum concentration of a vapor (usually expressed as the percentage of material in air) required to sustain a ﬁre. • Upper Explosive (or “Flammable”) Limit (UEL) - the maximum concentration of a vapor (usually expressed as the percentage of material in air) beyond which a ﬁre cannot be sustained, as the amount of oxygen would be insufﬁcient to continue the ﬁre. 9 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Terms & Abbreviations Explosive (or “Flammable”) Range - The range that encompasses any gas or vapor concentration between the substance’s lower explosive limit and upper explosive limit, and is therefore capable of sustaining combustion. Flammable Gas* - This term applies to a special group of combustible gases that ignite easily and burn rapidly. Flash Point - The minimum temperature at which a liquid gives off enough vapor to form an ignitable mixture with air (reaching 100% LEL). Gas - A state of matter characterized by very low density and viscosity (relative to liquids and solids), comparatively great expansion and contraction with changes in pressure and temperature, ability to diffuse readily into other gases, and ability to occupy with almost complete uniformity the whole of any container. (Often used interchangeably with “vapor”.) Gas Detection Instrument - A device composed of electrical, optical, mechanical or chemical components that senses and responds to the presence of gas mixtures. General Purpose (GP) Enclosure - An enclosure intended for indoor use in nonhazardous rated areas, primarily to prevent accidental contact of personnel with the enclosed equipment in areas where unusual service conditions do not exist. Hazardous Atmosphere - (As deﬁned by OSHA 29 CFR 1910.146) An atmosphere in which workers are exposed to the risk of death, injury, incapacitation or illness. Humidity - The amount of water vapor present in the atmosphere. IDLH (Immediately Dangerous to Life and Health)** The maximum concentration level of a substance (gas) from which a worker could escape within 30 minutes without developing immediate, severe or irreversible health effects, or other escape-impairing symptoms. IDLH levels are measured in ppm (parts per million). **As defined by NIOSH (National Institute for Occupational Safety and Health). * Any material that will burn at any temperature is considered to be “combustible”, so this term covers all such materials, regardless of how easily they ignite. The term “flammable” specifically refers to those combustible gases that ignite easily and burn rapidly. 10 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Terms & Abbreviations Interferent - Any gas other than the target gas that will cause a response from a gas sensor. Intrinsic Safety (IS) - A method of protection in which an explosion is prevented through an electrical design using energy storage devices in which the possibility of ignition is eliminated. LEL (Lower Explosive Limit) - (see “Explosive Limits”) Monitor - An instrument used to continuously measure a condition that must be kept within speciﬁc limits. NIOSH - National Institute for Occupational Safety and Health. OSHA - United States Department of Labor Occupational Safety and Health Administration. Oxygen Deficient Atmosphere - An atmosphere containing less than 19.5% oxygen by volume. (Possesses a risk of insufﬁcient oxygen for breathing.) Oxygen Enriched Atmosphere - An atmosphere containing more than 20.8% oxygen by volume. (Possesses an increased risk of explosion.) PEL (Permissible Exposure Limit) - An airborne concentration of contaminant that most workers can be exposed to repeatedly in a normal 8- hour day, in a 40-hour week, without adverse health effects. PEL levels are measured in ppm (parts per million) and are established by OSHA. Permanent (or Fixed) Gas Monitor - A gas monitor that is permanently installed in a location. PPM (Parts Per Million) - The most common unit of measurement for toxic gases. A “10,000 parts per million” gas concentration level equals a 1% by volume exposure. Relative Density - The density of a gas as compared to that of another gas (typically air). In gas detection, relative density is used to assist in determining optimum sensor placement. If the relative density of the monitored gas is less than 1, then it will tend to rise in air; if the relative density is greater than 1 then it will tend to sink in air and accumulate at ground level. 11 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Terms & Abbreviations Sensor - The part of a gas detector that converts the presence of a gas or vapor into a measurable signal. Smart Sensor - Sensor that contains a microprocessor, allowing it to record data, communicate with other devices or control devices such as relays. Span Check - (see “Bump Check”). STEL - Short-term exposure limit ( See “TLV - STEL”). TLV® (Threshold Limit Value)* - Refers to the airborne concentration of substances and represents conditions under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse health effects. * As defined by the ACGIH (American Conference of Governmental Industrial Hygienists). There are three categories of TLVs: TLV - TWA (Time Weighted Average) - This is the average amount of gas that a worker can be repeatedly exposed to in a normal 8-hour day, in a 40-hour week, without adverse health effects. TLV - STEL (Short Term Exposure Limit) -The gas concentration that most workers can be continuously exposed to for a 15-minute time period without suffering adverse health affects that would impair selfrescue or worker safety. This limit should not be repeated more than 4 times per day and there should be at least 60 minutes between individual STEL exposure periods. TLV - C (Ceiling) - The highest gas concentration to which workers may be exposed. Ceiling TLVs should never be exceeded and they take precedence over all TWAs and STELs. Toxic Atmosphere - An atmosphere in which the concentration of gases, dusts, vapors or mists exceeds the permissible exposure limit (PEL). Toxic Gas or Vapor - Substance that causes illness or death when inhaled or absorbed by the body in relatively small quantities. 12 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Terms & Abbreviations True Zero - A reading indicating that no amount of target gas is present in the sample. Also known as “baseline”. TWA - Time-weighted average (see “TLV-TWA”). UEL (Upper Explosive Limit) - (see “Explosive Limits”). Vapor - Often used interchangeably with “gas”; vapor is generally used to refer to the gaseous phase of a substance that generally exists as a liquid or solid at room temperature, while “gas” is more commonly used to refer to a substance that generally exists in the gaseous phase at room temperature. Vapor Density - the weight of a volume of pure gas or vapor compared to that of an equal volume of air at the same temperature and pressure. A vapor density of less than 1 indicates that the gas or vapor is lighter than air and will tend to rise. A vapor density of greater than 1 indicates that the vapor is heavier than air and will tend to accumulate closer to the ground. It may also move a signiﬁcant distance at these low levels to a source of ignition and then ﬂash back to the original location once ignited. When using vapor density to determine optimum sensor placement, other factors such as air ﬂow patterns and temperature gradients should also be considered. Vapor Pressure - The pressure exerted when a solid or liquid is in equilibrium with its own vapor. Vapor pressure is directly related to temperature. In gas detection, this is signiﬁcant because the higher the vapor pressure of a substance, the greater the amount of it that will be present in vapor phase at a given temperature, and thus a greater degree of gas hazard exists. Zero Check - Check performed to verify that the instrument reads true zero. Zero Gas - A cylinder of gas that is free of the gas of interest and interferents. It is used to properly zero an instrument’s base line. 13 Section 2 Gas Monitoring Categories Combustible Atmospheres Toxic Atmospheres Oxygen Deficiency Enrichment Atmospheres Gas Detection Technologies Gas Sampling M S A G a s D e t e c t i o n H a n d b o o k The Four Main Types of Gas Hazards The following table summarizes the four main reasons why gas monitoring is performed: Type of Monitoring The Purpose The Hazard Possible Source of Hazard Personal protection Worker safety Toxic gases Leaks, fugitive emissions, industrial process defects Explosive Worker and facility safety Explosions Presence of combustible gases/vapors due to leaks, industrial process defects Environmental Environmental safety Environmental degradation Oil leaks into sewers or lakes, Acid gas emissions Malfunction of the process Possible fault or other process error Industrial process Process control 16 M S A G a s D e t e c t i o n H a n d b o o k Gas Monitoring Categories Gas Monitoring Categories: 1. Combustible/ Flammable Gas • Explosive hazard. • To avoid an explosion, atmospheric levels must be maintained below the lower explosive limit (LEL) for each gas, or purged of oxygen. • Generally measured as 0-100% of the lower explosive limit or in part per million range. • Combustible gas monitors are designed to alarm before a potential explosive condition occurs. 2. Toxic/ Irritant Gases • Hazardous to human health; worker exposure must be monitored. • Typically measured in the part per million (ppm) range. • Toxic gas monitors are designed to alert workers before the gas level reaches a harmful concentration. • Some toxic gas monitors can calculate the average exposure over time, providing short-term exposure limit (STEL) and time-weighted average (TWA) readings. 3. Oxygen • Atmospheres containing too little oxygen (less than 19.5% oxygen by volume) are considered “oxygen deﬁcient” and interfere with normal human respiration. • Atmospheres containing too much oxygen (more than 25% oxygen by volume) are considered “oxygen enriched” and possess an increased risk of explosion. • Measured in the percent volume range (normal oxygen percentage in air is 20.8% by volume at sea level). • Oxygen monitors are generally set to alarm if the atmosphere contains either too little or too much oxygen. 17 M S A G a s D e t e c t i o n H a n d b o o k Combustible Atmospheres Combustible Atmospheres In order for a ﬂame to exist, three conditions must be met. There must be: • A source of fuel (e.g. methane or gasoline vapors). • Enough oxygen (greater than 10-15%) to oxidize or burn the fuel. • A source of heat (ignition) to start the process. Examples of Heat and Ignition Sources • Open ﬂames such as those from lighters, burners, matches and welding torches are the most common sources of ignition. • Radiation in the form of sunlight or coming from hot surfaces. • Sparks from various sources such as the switching on or off of electric appliances, removing plugs, static electricity or switching relays. 18 M S A G a s D e t e c t i o n H a n d b o o k Combustible Atmospheres Combustible Atmosphere Factors Vapor vs. Gas Though often used interchangeably, the terms “vapor” and “gas” are not identical. The term “vapor” is used to refer to a substance that, though present in the gaseous phase, generally exists as a liquid or solid at room temperature. When we say that a liquid or solid substance is burning, it is actually its vapors that burn. “Gas” refers to a substance that generally exists in the gaseous phase at room temperature. Vapor Pressure and Boiling Point Vapor pressure is the pressure exerted when a solid or liquid is in equilibrium with its own vapor. It is directly related to temperature. An example of vapor pressure is the pressure developed by the vapor of a liquid in a partially-ﬁlled closed container. Depending on temperature, the vapor pressure will increase up to a certain threshold. When this threshold is reached, the space is considered to be saturated. The vapor pressure and boiling point of a chemical determine how much of it is likely to become airborne. Low vapor pressure means there are less molecules of the substance to ignite, so there is generally less of a hazard present. This also means that there are less molecules to sense, which may make detection more challenging and require higher-sensitivity instrumentation. With higher vapor pressure and a lower boiling point, there is a greater likelihood of evaporation. If containers of chemicals with such properties are left open, or if they’re allowed to spread over large surfaces, they are likely to cause greater hazards. Flashpoint A ﬂammable material will not give off an amount of gas or vapor sufﬁcient to start a ﬁre until it is heated to its ﬂashpoint. Flashpoint is deﬁned as the lowest temperature at which a liquid produces sufﬁcient vapor to produce a ﬂame. If the temperature is below this point, the liquid will not produce enough vapor to ignite. If the ﬂashpoint is reached and an external source of ignition such as a spark is provided, the material will catch ﬁre. The National Fire Protection Agency’s NFPA’s document NFPA-325M, Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solvents, lists the ﬂashpoints of many common substances. See www.nfpa.org. 19 M S A G a s D e t e c t i o n H a n d b o o k Combustible Atmospheres Flash points are signiﬁcant because they give an indication of the degree of hazard presented by a ﬂammable liquid. Generally, the lower the ﬂash point, the easier it is for ﬂammable fuel-air mixtures to form, and thus the greater hazard. Autoignition Temperature If heated to a certain point—the spontaneous ignition (or “autoignition”) temperature—most ﬂammable chemicals can spontaneously ignite under its own heat energy, without an external source of ignition. 20 M S A G a s D e t e c t i o n H a n d b o o k Combustible Atmospheres Vapor Density Vapor density is the weight ratio of a volume of ﬂammable vapor compared to an equal volume of air. Most ﬂammable vapors are heavier than air so they gravitate toward the ground, settling in low areas. A gas or vapor with a vapor density greater than 1 may travel at low levels to ﬁnd a source of ignition (e.g. hexane, which has a 3.0 vapor density); a gas or vapor with a vapor density less than 1 will tend to rise (e.g. methane, which has a 0.6 vapor density). Vapor density is important to consider when determining optimum sensor placement because it helps predict where the gas or vapor is most likely to accumulate in a room or area. Explosive Limits To produce a ﬂame, a sufﬁcient amount of gas or vapor must exist. But too much gas can displace the oxygen in an area and fail to support combustion. Because of this, there are limits at both low-end and high-end gas concentrations where combustion can occur. These limits are known as the Lower Explosive Limit (LEL) and the Upper Explosive Limit (UEL). They are also referred to as the Lower Flammability Limit (LFL) and the Upper Flammability Limit (UFL). To sustain combustion, the atmosphere must contain the correct mix of fuel and oxygen (air). The LEL indicates the lowest quantity of gas which must be present for combustion and the UEL indicates the maximum quantity of gas. The actual LEL level for different gases may vary widely and are measured as a percent by volume in air. Gas LELs and UELs can be found in NFPA 325. LELs are typically 1.4% to 5% by volume. As temperature increases, less energy is required to ignite a ﬁre and the percent gas by volume required to reach 100% LEL decreases, increasing the hazard. An environment containing enriched oxygen levels raises the UEL of a gas, as well as its rate and intensity of propagation. Since mixtures of multiple gases add complexity, their exact LEL must be determined by testing. Most combustible gas instruments measure in the LEL range and display gas readings as a percentage of the LEL. For example: a 50% LEL reading means the sampled gas mixture contains one-half of the amount of gas necessary to support combustion. 21 M S A G a s D e t e c t i o n H a n d b o o k Combustible Atmospheres Gas Type 100% LEL UEL Methane 5.0% gas by volume 15.0% gas by volume Hydrogen 4.0% gas by volume 75.0% gas by volume Propane 2.1% gas by volume 9.5% gas by volume Acetylene 2.5% gas by volume 100% gas by volume Any gas or vapor concentration that falls between these two limits is in the ﬂammable (explosive) range. Different substances have different ﬂammable range widths — some are very wide and some are narrower. Those with a wider range are generally more hazardous since a larger amount of concentration levels can be ignited. Atmospheres in which the gas concentration level is below the LEL (insufﬁcient fuel to ignite) are referred to as too “lean” to burn; those in which the gas level is above the UEL (insufﬁcient oxygen to ignite) are too “rich” to burn. 22 M S A G a s D e t e c t i o n H a n d b o o k Toxic Atmospheres Toxic Gas Monitoring A toxic gas is one which is capable of causing damage to living tissue, impairment of the central nervous system, severe illness or—in extreme cases—death, when ingested, inhaled or absorbed by the skin or eyes. The amounts required to produce these results vary widely with the nature of the substance and exposure time. “Acute” toxicity refers to exposure of short duration, such as a single brief exposure. “Chronic” toxicity refers to exposure of long duration, such as repeated or prolonged exposures. Toxic gas monitoring is important because some substances can’t be seen or smelled and have no immediate effects. Thus the recognition of a gas hazard via a worker’s senses often comes too late, after concentrations have reached harmful levels. The toxic effects of gases range from generally harmless to highly toxic. Some are life-threatening at even short, low-level exposures, while others are hazardous only upon multiple exposures at higher concentrations. The degree of hazard that a substance poses to a worker depends upon several factors which include the gas concentration level and the duration of exposure. Exposure Limits The American Conference of Governmental Industrial Hygienists (ACGIH) publishes an annually revised list of recommended exposure limits for common industrial compounds, titled “TLV“s and BEI“s Based on the Documentation of the Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices”. (To order a copy, see www.acgih.org). ACGIH developed the concept of Threshold Limit Value“ (TLV), which is deﬁned as the airborne concentration of a contaminant to which it is believed that almost all workers may be repeatedly exposed, day after day, over a working lifetime without developing adverse effects. These values are based on a combination of industrial experience and human and animal research. Time Weighted Averages (TWAs) TLVs are generally formulated as 8-hour time-weighted averages. The averaging aspect enables excursions above the prescribed limit as long as they are offset by periods of exposure below the TLV. 23 M S A G a s D e t e c t i o n H a n d b o o k Toxic Atmospheres Short-Term Exposure Limits (STELs) Short-term exposure limits are concentrations above the 8-hour average to which workers may be exposed for short periods of time without harmful effects. (If the concentration is high enough, even a one-time exposure can produce harmful health effects.) STELs are used to govern situations in which a worker is exposed to a high gas concentration, but only for a short period of time. They are deﬁned as 15-minute time-weighted averages that are not to be exceeded even if the 8-hour TWA is below the TLV. Ceiling Concentrations For some toxic gases, a single exposure exceeding the TLV may be hazardous to worker health. In these cases, ceiling concentrations are used to indicate levels that are never to be exceeded. Permissible Exposure Limits (PELs) PELs are enforced by the Occupational Safety and Health Administration (OSHA). Part 29 of the Code of Federal Regulations (CFR) Section 1910.1000 contains these standards, which are similar to ACGIH TLVs except that they are legally enforceable rather than simply recommendations. However, the most accurate PELs are listed in the associated Material Safety Data Sheets (MSDS). Immediately Dangerous to Life and Health (IDLH) The National Institute for Occupational Safety and Health (NIOSH) deﬁnes an IDLH exposure condition atmosphere as one that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment. Since IDLH values exist to ensure that a worker can escape from a hazardous environment in the event of failure of respiratory protection equipment, they are primarily used to determine appropriate respiratory selection in compliance with OSHA standards. 24 M S A G a s D e t e c t i o n H a n d b o o k Toxic Atmospheres Web resources: ACGIH: http://www.acgih.org/TLV OSHA: http://www.osha.gov NIOSH: http://www.cdc.gov/niosh/homepage.html Gas detection systems are used to monitor toxic gases in primarily two types of monitoring applications: 1. Ambient air monitoring (includes leak monitoring) • low-level gas detection for worker safety • to reduce leakage of expensive compounds (e.g., refrigerants) 2. Process monitoring • to monitor levels of compounds used in chemical synthesis processes (e.g., in the plastics, rubber, leather and food industries) • from low ppm levels to high % by volume levels For toxic gas monitoring, electrochemical, metal oxide semiconductor (solid state), infrared and photoionization are the sensing technologies most commonly used. 25 M S A G a s D e t e c t i o n H a n d b o o k Oxygen Deficiency/Enrichment Oxygen Deficiency Normal ambient air contains an oxygen concentration of 20.8% by volume. When the oxygen level dips below 19.5% of the total atmosphere, the area is considered oxygen deﬁcient. In oxygen-deﬁcient atmospheres, life-supporting oxygen may be displaced by other gases, such as carbon dioxide. This results in an atmosphere that can be dangerous or fatal when inhaled. Oxygen deﬁciency may also be caused by rust, corrosion, fermentation or other forms of oxidation that consume oxygen. As materials decompose, oxygen is drawn from the atmosphere to fuel the oxidation process. The impact of oxygen deﬁciency can be gradual or sudden, depending on the overall oxygen concentration and the concentration levels of other gases in the atmosphere. Typically, decreasing levels of atmospheric oxygen cause the following physiological symptoms: % Oxygen 19.5 - 16 Physiological Effect No visible effect. 16 - 12 Increased breathing rate. Accelerated heartbeat. Impaired attention, thinking and coordination. 14 – 10 Faulty judgment and poor muscular coordination. Muscular exertion causing rapid fatigue. Intermittent respiration. 10 – 6 Nausea and vomiting. Inability to perform vigorous movement, or loss of the ability to move. Unconsciousness, followed by death. Below 6 Difﬁculty breathing. Convulsive movements. Death in minutes. Oxygen Enrichment When the oxygen concentration rises above 20.8% by volume, the atmosphere is considered oxygen-enriched and is prone to becoming unstable. As a result of the higher oxygen level, the likelihood and severity of a ﬂash ﬁre or explosion is signiﬁcantly increased. 26 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Gas Detection Technologies There are a variety of gas detection technologies in use today. Among the most commonly employed are: • Catalytic Bead • Metal Oxide Semiconductor (also known as “solid state”) • Point Infrared Short Path • Open (Long Path) Infrared • Photoacoustic Infrared • Electrochemical for Toxic Gas Detection • Electrochemical for Oxygen Detection • Thermal Conductivity • Photoionization • NDIR The tables and diagrams on the following pages summarize the operation of each technology. 27 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Catalytic bead Gas Type Detected Combustible gas Principle of Operation Uses a catalytic bead to oxidize combustible gas; a Wheatstone Bridge converts the resulting change in resistance into a corresponding sensor signal. A wire coil is coated with a catalyst-coated glass or ceramic material, and is electrically heated to a temperature that allows it to burn (catalyze) the gas being monitored, releasing heat and increasing the temperature of the wire. Description - As the temperature of the wire increases, so does its Detailed electrical resistance. This resistance is measured by a Wheatstone Bridge circuit and the resulting measurement is converted to an electrical signal used by gas detectors. A second sensor, the compensator, is used to compensate for temperature, pressure and humidity. Readings % LEL Pros Long life, less sensitive to temperature, humidity, condensation and pressure changes; high accuracy; fast response; monitors a wide range of combustible gases and vapors in air. Cons Subject to sensor poisoning; requires air or oxygen; shortened life with frequent or continuous exposure to high LELs. 28 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Catalytic Bead Sensor Operation 29 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Metal Oxide Semiconductor Gas Type Detected Combustible gas; Toxic gas Principle of Operation Made of a metal oxide that changes resistance in response to the presence of a gas; this change is measured and translated into a concentration reading. A semiconducting material (metal oxide) is applied to a nonconducting substance (substrate) between two electrodes. The substrate is heated to a temperature at which the presence of the gas can cause a reversible change in the conductivity of the semi-conducting material. When no gas is Description present, oxygen is ionized onto the surface and the sensor Detailed becomes semi-conductive; when molecules of the gas of interest are present, they replace the oxygen ions, decreasing the resistance between the electrodes. This change is measured electrically and is proportional to the concentration of the gas being measured. Readings PPM Pros High sensitivity (detects low concentrations); wide operating temperature range; long life. Cons Non-speciﬁc (cross-sensitive to other compounds); nonlinear output; sensitive to changes in humidity: subject to poisoning. 30 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Metal Oxide Semiconductor (Solid State) Sensor Operation Silicon Chip Sensor Film Heater 31 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Point Infrared Short Path Gas Type Detected Combustible gas Principle of Operation [Also referred to as Non-Dispersive Infrared (NDIR)]; Absorptive IR uses a gas ability to absorb IR radiation. Two gas samples--the gas of interest, and an inert reference gas--are exposed to infrared light. The amount of light transmitted through each sample is compared to determine the concentration of the gas of interest. Uses an electrically modulated source of infrared energy and two detectors that convert the infrared energy into electrical signals. Each detector is sensitive to a different range of wavelengths in the infrared portion of the spectrum. The source emission is directed through a window in the main enclosure into an open volume. A mirror may be used at the Description - end of this volume to direct the energy back through the Detailed window and onto the detectors. The presence of a combustible gas will reduce the intensity of the source emission reaching the analytical detector, but not the intensity of emission reaching the reference detector. The microprocessor monitors the ratio of these two signals and correlates this to a %LEL reading. Readings % LEL Pros High accuracy and selectivity; large measurement range; low maintenance; highly resistant to chemical poisons; does not require oxygen or air; span drift potential virtually eliminated (no routine calibration required); fail-to-safe. Compared to open-path IR, provides exact gas level (but at point of detection only). Cons 32 Not suitable for hydrogen detection. M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Point Infrared Short Path Operation 33 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Open Path Infrared Gas Type Detected Combustible gas Principle of Operation Operates similarly to point infrared detectors, except that the IR source is separated from the detector. Open-path IR monitors expand the concepts of point IR detection to a gas sampling path of up to 100 meters. Like point IR monitors, they utilize a dual beam concept. The "sample" beam is in the infrared wavelength which absorbs hydrocarbons, while the second "reference" beam is outside this gas absorbing wavelength. The ratio of the two beams is Description continuously compared. When no gas is present, the signal Detailed ratio is constant; when a gas cloud crosses the beam, the sample signal is absorbed or reduced in proportion to the amount of gas present while the reference beam is not. System calculates the product of the average gas concentration and the gas cloud width, and readings are given in %LEL/meter. Readings % LEL per meter Pros High accuracy and selectivity; large measurement range; low maintenance; highly resistant to chemical poisons; does not require oxygen or air; span drift potential virtually eliminated (no routine calibration required); fail-to-safe. Not suitable for hydrogen detection. Cons Compared with point IR detection, is not capable of isolating the leak source. Requires unobstructed path between source and detector. 34 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Open Long Path Infrared Operation 35 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Photoacoustic Infrared Gas Type Detected Combustible gas; Toxic gas Principle of Operation Uses a gases ability to absorb IR radiation and the resulting change in pressure. The gas sample is exposed to infrared light; as it absorbs Description - light its molecules generate a pressure pulse. The magnitude Detailed of the pressure pulse indicates the gas concentration present. Readings % LEL, % by volume, PPM, PPB Pros High sensitivity; linear output; easy to handle; not subject to poisoning; long-term stability. Cons Not suitable for hydrogen detection. 36 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Pumped Photoacoustic Infrared Operation (Diffusion method also available) Sample gas enters the measuring cell. The gas is irradiated with pulsed infrared energy. 37 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies The gas molecules heat and cool as they absorb the infrared energy. The pressure changes as a result of the heating and cooling of the molecules measured by the detector. This pressure change is converted into a gas reading. The gas is exhausted and a fresh sample enters the cell. This sampling process is continuously repeated. 38 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Electrochemical Toxic Gases Gas Type Detected Toxic gas Principle of Operation Uses an electrochemical reaction to generate a current proportional to the gas concentration. Sensor is a chamber containing a gel or electrolyte and two active electrodes--the measuring (sensing/working) electrode (anode) and the counter electrode (cathode). A third electrode (reference) is used to build up a constant Description - voltage between the anode and the cathode. The gas sample Detailed enters the casing through a membrane; oxidation occurs at the anode and reduction takes place at the cathode. When the positive ions ﬂow to the cathode and the negative ions ﬂow to the anode, a current proportional to the gas concentration is generated. Readings PPM readings for toxic gases Pros High sensitivity; linear output; easy to handle. Cons Limited shelf life; subject to interferents; sensor lifetime shortened in very dry and very hot environments. 39 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Electrochemical Toxic Sensor 40 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Electrochemical Oxygen Gas Type Detected Oxygen deﬁciency/ enrichment Principle of Operation Uses an electrochemical reaction to generate a current proportional to the gas concentration. Sensor is a chamber containing a gel or electrolyte and two electrodes--the measuring (sensing/working) electrode and the (usually lead) counter/reference electrode. The gas Description - sample enters the casing through a membrane; oxidation Detailed occurs at the anode and reduction takes place at the cathode. When the positive ions ﬂow to the cathode and the negative ions ﬂow to the anode, a current proportional to the gas concentration is generated. Readings Percent volume readings for oxygen Pros High sensitivity; linear output; easy to handle; not subject to poisoning. Cons Limited shelf life; subject to interferents; sensor life shortened in very dry and very hot environments, or in enriched O2 applications. 41 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Electrochemical Oxygen Sensor 42 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Gas Type Detected Principle of Operation Thermal Conductivity Combustible gas; Toxic gases Measures the gas sample's ability to transmit heat by comparing it with a reference gas (usually air). Two sensors (detecting sensor and compensating sensor) are built into a Wheatstone Bridge. The detecting sensor is exposed to the gas of interest; the compensating sensor is enclosed in a sealed compartment ﬁlled with clean air. Description - Exposure to the gas sample causes the detecting sensor to Detailed cool, changing the electrical resistance. This change is proportional to the gas concentration. The compensating sensor is used to verify that the temperature change is caused by the gas of interest and not by ambient temperature or other factors. Readings PPM; up to 100% by volume Pros Wide measuring range. Cons Non-speciﬁc (cross-sensitive to other compounds); does not work with gases with thermal conductivities (TCs) close to one (that of air, NH3, CO, NO, O2, N2); gases with TCs of less than one are more difﬁcult to measure; output signal not always linear. 43 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Thermal Conductivity Sensor 44 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Technology Photoionization Gas Type Detected Toxic (organic compounds) Principle of Operation Uses ionization as the basis of detection. A photoionization detector (PID) uses an ultraviolet lamp to ionize the compound of interest. Ions are collected on a Description ‘getter’, a current is produced and the concentration of Detailed the compound is displayed in parts per million on the instrument meter. Readings PPM, sub-ppm Pros Fast response speed, very low level detection, detects a large number of substances. Cons More expensive, increased maintenance, requires more frequent calibration, non-speciﬁc, sensitive to humidity. 45 M S A G a s D e t e c t i o n H a n d b o o k Gas Detection Technologies Typical Photoionization Sensor Design 46 M S A G a s D e t e c t i o n H a n d b o o k Gas Sampling Gas Sampling There are three methods of gas sampling: • Diffusion Sampling • Pumped Sampling • Aspirated Sampling Diffusion Sampling Diffusion is the natural movement of molecules away from an area of high concentration to an area of lower concentration. The term “diffusion” denotes the process by which molecules or other particles intermingle as a result of their random thermal motion. Ambient conditions such as temperature, air currents and other characteristics affect diffusion. Advantages: • Most effective placement is at desired sampling point. • Fast response because no sample transport is required. • No pumps and/or ﬁlters to maintain. Pumped Sampling Pumped sampling uses a pump to pull the sample from a remote location into or through the sensor. With pumped sampling, samples can be gathered simultaneously from two or more locations. 47 M S A G a s D e t e c t i o n H a n d b o o k Gas Sampling Conditions Favoring Pumped Sampling: • Sampling point is too hot/cold. • Sampling point is difﬁcult to access. • Heavy vapor present that does not diffuse well by natural forces. • An application can be converted from an explosionproof (XP) rating to a general purpose (GP) rating through pumped operation. (Flashback arrestors may be necessary between the sample port and the sensor.) • Conﬁned Spaces Aspirated Sampling Aspirated sampling uses suction to draw the sample from a remote location into or through the sensor. Advantages of Aspirated Sampling Versus Pumped: • Lower cost • Reduced maintenance because there are no moving parts 48 Section 3 Gas Information Table 50 Synonym Acroleic acid Acrylic acid Heavier Heavier C3H4O2 C2H3N X X X X 3.0 2.0 2.8 2.8 2.0 17 8 31 31 8 100 16 12.8 2 2 - - 2 A 20 500 - 10 Ca = Carcinogen 0 50 -26 -26 50 2.5 3.0 2.5 60 19.9 2 - 0.1 0.1 - - 40 1,000 200 10 200 85 - 2 2 - - 500 2,500 2,000 50 2,000 X X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - 0.1 [C] 0.1 [C] - A - 750 25 [C] 15 25 [C] Electrochemical A = Asphyxiant Heavier Heavier X Gas 6 -20 4.0 4.0 - 481 438 220 220 438 305 524 465 175 463 175 77 142 52 52 142 -83 82 56 21 118 21 83 3 210 210 3 73 750 11 750 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Acrylonitrile Acrylaldehyde Acrolein Acrolein Acrylaldehyde C3H4O Heavier C3H4O2 Acrylic acid X X -38 39 60 Autoignition Temp (°C)* D e t e c t i o n C3H4O Lighter C2H2 Acetylene Acroleic acid Heavier X Heavier C3H6O C2H3N Acetone Acetonitrile X Heavier C2H4O Aceticaldehyde X Heavier C2H4O2 Acetaldehyde Combustible 4.0 Catalytic -38 Photoacoustic IR X Absorptive IR Acetic Acid Heavier C2H4O Semiconductor Acetic aldehyde Relative Density (vs.Air)+ Chemical Formula ACGIHT ACGIHT Flash LEL UEL OSHA NIOSH LVLV Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Acetaldehyde Gas or Vapor Gas Information Table M S A H a n d b o o k C6H5Cl Benzene chloride Chlorobenzene Methylbromide Halon 1301 Bromomethane Bromotriﬂuoro methane CBrF3 Heavier Heavier Heavier Heavier X X X A = Asphyxiant CH3Br CF2ClBr Heavier Heavier X X X n/a 10.0 n/a n/a 1.3 1.3 5.1 1.1 15.0 2.9 n/a 16 n/a n/a 9.6 7.1 78 7.5 28 11.1 2.5 - 0.5 10 1,000 1 - - 3 1,000 500 3 1,000 300 250 20 1,000 - 20 [C] 250 [Ca] - 0.1 75 10 0.05 100 50 1 2 X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - - 0.2 - 0.1 - - 35 2 - 0.05 25 1 0.5 Ca = Carcinogen n/a n/a n/a n/a 29 -11 Gas 16 Gas -32 18 - 537 - 638 498 360 651 392 378 295 17 -58 4 3.3 59 132 80 -62 149 12,153 @ 25°C 1,250 778 175 12 75 >760 -33 400 @ 45°C 45 97 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Halon 1211 Bromochlorodi ﬂuoromethane Br2 C6H6 Benzeneˆ Heavier Heavier Lighter X 2.5 Autoignition Temp (°C)* D e t e c t i o n Bromine AsH3 C7H14O2 Arsine Amyl acetate, n- NH3 Heavier 21 Electrochemical Ammonia C3H5Cl Combustible X Catalytic Heavier Photoacoustic IR C3H6O Absorptive IR Allyl Chloride Synonym Relative Density (vs.Air)+ Semiconductor 2-propenyl Chemical Formula ACGIHT ACGIHT Flash LEL UEL LV OSHA NIOSH LVPoint (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Allyl alcohol Gas or Vapor Gas Information Table M S A H a n d b o o k 51 52 Heavier Heavier Heavier Heavier Heavier Heavier Heavier Heavier Heavier C4H10 C4H10O C4H10O C4H8O C6H12O2 C6H12O2 C6H12O2 C6H12O2 C4H10 C6H12 Butyl alcohol Butyl alcohol Methylethylketone Butane, n- Butanol, n- Butanol, sec- Butanone, 2- Butyl acetate, n- Butyl acetate, sec- Butyl acetate, tert Butyl acrylate, n- Butyl alcohol, n- Butanol, n- Butyl ethylene hexylene Hexene, 1- 1.2 1.4 1.5 1.5 1.7 1.3 1.4 1.7 1.4 1.5 6.9 11.2 9.9 - 9.8 7.6 11.4 9.8 11.2 8.5 50 20 2 200 200 150 200 100 20 800 - 100 - 200 200 150 200 150 100 - - 1,400 - 1,500 1,700 1,700 3,000 2,000 1,400 - X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - - - - 200 300 - - - 2,000 Electrochemical Ca = Carcinogen -26 29 29 22 17 22 -9 24 29 Gas 1 253 343 267 - - 420 404 405 343 287 420 Gas 63 308 @ 38°C 117 127 112 127 80 94 117 -1 -4 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X X Thermal Conductivity A = Asphyxiant X X X X X X X X X X (-) Autoignition Temp (°C)* D e t e c t i o n Key: [C] = Ceiling Limit (never exceed) Combustible 2 Catalytic 11.5 Photoacoustic IR 2.0 Absorptive IR -76 Semiconductor X ACGIHT ACGIHT Flash LEL UEL OSHA NIOSH LVLV Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Heavier Heavier C4H10 Synonym Butadienes Gas or Vapor Relative Density (vs.Air)+ Chemical Formula Gas Information Table M S A H a n d b o o k Ethyl chloride Chloroethane Key: [C] = Ceiling Limit (never exceed) Heavier Heavier Heavier X X A = Asphyxiant C2H5Cl ClO2 C6H5Cl Benzene chloride Chlorobenzene Heavier X X 3.8 1.3 n/a - n/a n/a 12.0 1.3 15.4 9.6 n/a n/a n/a n/a 75 50 n/a 100 10 1,000 75 0.1 1 [C] 0 10 50 20 5,000 - 3,800 1,000 5 10 2 200 1,200 500 40,000 - X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - 0.3 1 0.5 0.1 - 0.1 10 5 - 30,000 25 10 5,000 Ca = Carcinogen -50 29 n/a Gas n/a n/a Gas -30 n/a - X 519 638 - - - - 609 90 - 218 12 132 -34 8 77 -192 46 76 12 Gas 568 @ 0°C 91 >760 300 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X Autoignition Temp (°C)* D e t e c t i o n Chlorine dioxide Cl2 COCl2 Carbonyl chloride Phosgene Chlorine Heavier Heavier Slightly lighter CO CCl4 Carbon tetrachloride Tetrachloromethane Heavier n/a - Electrochemical Carbon monoxide CS2 Carbon disulﬁde Heavier 12.5 Thermal Conductivity CO2 Combustible 1.9 Catalytic -22 Photoacoustic IR X Absorptive IR Heavier Relative Density (vs.Air)+ Semiconductor C4H8O Chemical Formula ACGIHT ACGIHT Flash LEL UEL LV OSHA NIOSH LVPoint (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Carbon dioxide Synonym Butylaldehyde: butanal Gas or Vapor Butyraldehyde Gas Information Table M S A H a n d b o o k 53 54 Heavier Heavier C2H4Cl2 C4H10O Dichloroethane .1,2- Ethylen dichloride Diethyl ether Key: [C] = Ceiling Limit (never exceed) X X 1.9 6.2 5.4 2.2 0.8 1.8 1.1 8 36 15.9 11.4 9.2 98 6.9 8.7 9.4 400 10 100 25 0.1 50 600 25 100 50 50 Ca = Carcinogen -45 13 -17 66 X X 58 -90 X X 1.3 1.1 6.5 17.4 400 50 100 50 [C] 0.1 50 - 50 300 50 100 50 [C] 1,900 50 [C] 3,000 200 15 1,800 - 700 1,300 500 2,000 500 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available 500 - - 50 - - - - - - 100 - 160 413 458 648 38-52 603 361 420 245 425 632 - 3.2 160 35 84 57-59 180 442 100 @ 29°C 1.2 -93 224 @ 112°C 164 49 156 82 152 -24 62 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X Thermal Conductivity A = Asphyxiant Heavier Ethyl ether Heavier C6H4Cl2 C2H4Cl2 B2H6 -37 43 -20 0.9 -50 10 Electrochemical Dichloroethane .1,1- Ethylidene dichloride Heavier Slightly heavier C6H12O2 X X X 33 Gas n/a Autoignition Temp (°C)* D e t e c t i o n Dichlorobenzene, o- Diacetone Boroethane Diborane Heavier C5H10 Cyclopetane Diacetone alcohol Heavier Heavier C6H12 X X Combustible C6H10O Heavier C9H12 Isopropylenzene Cumene n/a Catalytic Cyclohexanone Heavier CH3Cl Methyl chloride Chloromethane n/a Semiconductor Cyclohexane Heavier Photoacoustic IR CHCl3 Synonym Absorptive IR Trichloromethane Relative Density (vs.Air)+ Chemical Formula ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Chloroform Gas or Vapor Gas Information Table M S A H a n d b o o k X Heavier X X X X Heavier Heavier Heavier Heavier Heavier C4H9NO C2H6O C2H7N C2H11N C3H7NO DME DMA Dimethyl acetamide Dimethyl ether Dimethylamine Dimethylethylamine Dimethylformamide DMF 2.2 0.9 2.8 3.4 1.8 12.7 15.2 11.2 14.4 27 11.5 33.4 7.1 - 10.1 10 - 5 - 10 - 5 - 5 200 10 - 10 - 10 - 5 - 25 - 500 - 500 - 300 - 200 - 200 - X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - 15 - - - - - 15 300 Electrochemical Ca = Carcinogen 57 -45 Gas Gas 70 n/a 0.8 - 1.8 6.4 445 190 430 350 490 647 316 380 312 450 153 36 7 -24 165 -52 84 181 56 103 - 1500 @ 25°C 1, 4 11,377 @ 21°C 60 0.75 194 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X Thermal Conductivity A = Asphyxiant X X Heavier CH2F2 Diﬂuoromethane HFC-32 -6 55 -28 1.6 Autoignition Temp (°C)* D e t e c t i o n Key: [C] = Ceiling Limit (never exceed) X Heavier C10H14 C6H15N Dowtherm J Diethylbenzene X Heavier C4H11N Diisopropylamine Diethamine Diethylamine Combustible 12 Catalytic X Photoacoustic IR Heavier Absorptive IR C5H10O Relative Density (vs.Air)+ Semiconductor DEK Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Diethyl ketone Gas or Vapor Gas Information Table M S A H a n d b o o k 55 56 Heavier Heavier Heavier Heavier Heavier C2H4 C4H10O2 C4H8O2 C5H8O2 C2H6O C8H10 Ethene Ethoxyethanol, 2- Cellosolve Ethyl acetate Ethyl acrylate Ethanol X X 31 3.8 1.0 3.3 1.4 2.0 1.7 2.7 3.0 6.7 19 14 11.5 15.6 100 1,000 5 400 5 A A 3.6 0.5 21 12.5 (15.5) - - - - 100 1,000 25 400 200 - - 5 - 100 - 800 3,300 300 [Ca] 2,000 500 - A 75 - 500 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available 125 - 15 - - A A - - - - Electrochemical Ca = Carcinogen 21 12 9 -4 43 Gas Gas - 22 42 215 432 363 372 427 235 490 472 411 380 180 136 78 100 77 135 -104 -89 116 181 101 189 7 31 13 0.75 29 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Ethylbenzene Ethyl alcohol X X X X X X - 2.0 2.6 Autoignition Temp (°C)* D e t e c t i o n A = Asphyxiant Slightly lighter C2H6 Ethylene Heavier Slightly heavier C3H5OCl Epichlorohydrin Ethane Heavier C10H14 Diethylbenzene Dowtherm J 55 12 Catalytic X 94 X Heavier Combustible C4H8O2 Photoacoustic IR C2H6SO Absorptive IR Diethylene dioxide Relative Density (vs.Air)+ Semiconductor Dimethylsulfoxide Synonym Chemical Formula ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Dioxane Gas or Vapor Gas Information Table M S A H a n d b o o k Ethene 1,2 dichloroethylene Ethylene Ethylene dichloride - A = Asphyxiant X 1.4 7.6 19.3 n/a 11.4 100 15.3 300 2 1 100 1 - 10 A 400 Ca = Carcinogen -42 Heptane, Hexane Gasoline 2.1 n/a 5.4 3.0 3.2 15.9 3.6 36 100 - 5 0.1 100 [Ca] 100 25 3,000 X 800 [Ca] X - 50 [Ca] - 1,900 3,800 X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available 500 - 2 - 1 - 100 mg/m3 - 50 - 400 1,000 - A 500 - 316 429 458 429 398 413 490 160 519 162 -188 57-59 11 197 84 -104 35 12 2 1,095 100 @ 29°C 442 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) 60 X Heavier C5H4O2 Furfurol Furfural -17 n/a X -20 Heavier C2H3Cl2 Heavier X Heavier C2H4O 111 F2 Dichloroethane, 1, 1- X Heavier C2H6O2 6.2 2.7 1.9 15.4 Autoignition Temp (°C)* D e t e c t i o n Fluorine EtO Ethylidene dichloride X Heavier C2H4Cl2 13 Gas Slightly lighter X C2H4 -45 X Heavier C4H10O 3.8 Electrochemical Ethylene oxide Ethylene glycol Diethyl ether Ethyl ether Combustible -50 Catalytic X Photoacoustic IR Heavier Absorptive IR C2H5Cl Relative Density (vs.Air)+ Semiconductor Chloroethane Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Ethyl chloride Gas or Vapor Gas Information Table M S A H a n d b o o k 57 58 C6H12O C6H12 Methyl butyl ketone Butyl ethylene hexylene Hexanone, 2- Hexene, 1- Heavier Heavier Heavier X X 1.2 1.2 n/a n/a 7 6.9 8 n/a n/a 73 6.7 50 5 - - - 400 1,000 - 100 - - - 500 1,000 - - 1,600 - - - 750 - - X X X X X X X X X X X X X X X X X X X - = Data not currently available - 10 - - - 500 - - Electrochemical Ca = Carcinogen -26 25 n/a n/a - 1.1 n/a - 253 423 - - - 204 63 128 -30 -30 6 98 -58 -3.3 308 @ 38°C 4,800 4,800 1,293 12,153 @ 25°C 778 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X Thermal Conductivity A = Asphyxiant C3F6 Hexaﬂuoropropene Hesaﬂuoropropylene Heavier X -4 n/a n/a Autoignition Temp (°C)* D e t e c t i o n Key: [C] = Ceiling Limit (never exceed) C3F6 Hexaﬂuoropropylene C4F6 Hexaﬂuoro 1,3 butadiene X Combustible Hexaﬂuoropropene Heavier C7H16 Heptane, n- n/a n/a Catalytic Heavier Heavier CBrF3 Bromotriﬂuoromethane Halon 1301 n/a Photoacoustic IR Heavier Absorptive IR CF2ClBr Relative Density (vs.Air)+ Semiconductor Halon 1211 Synonym Chemical Formula ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Bromochlorodiﬂuoromethane Gas or Vapor Gas Information Table M S A H a n d b o o k Key: [C] = Ceiling Limit (never exceed) HBr Hydrogen bromide Hydrobromic acid H2 X A = Asphyxiant Heavier Lighter n/a 4.0 n/a n/a 75 n/a - - A - - - Ca = Carcinogen n/a Gas n/a Heavier - n/a - 3 - 3 - - - - 30 - 30 - - - - X X X X X X X X X X X X X - = Data not currently available 3 [C] A 3 [C] - - - - s X 400-253 405 n/a 647 245 74 74 61 36 -52 67 Gas 202 @ 25°C 500 @ 22°C 11,377 @ 21°C 310 @ 38°C Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X Thermal Conductivity Hydrogen - Heavier n/a 33.4 - Autoignition Temp (°C)* D e t e c t i o n Hydrocarbons (see speciﬁc) HBr - Heavier 12.7 - Electrochemical Hydrobromic acid Hydrogen bromide HFE 7100 C4F7OH3 n/a X - Semiconductor HFE 347E CH2F2 Diﬂuoromethane HFC - 32 Combustible <-7 Catalytic X Photoacoustic IR Heavier Relative Density (vs.Air)+ Absorptive IR C6H12 Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Hexane, 2- Gas or Vapor Gas Information Table M S A H a n d b o o k 59 60 X Lighter Heavier Heavier Heavier Heavier HF H2S C5H12O C4H10 C6H12O2 Hydrogen ﬂuoride Hydrogen sulﬁde Isoamyl alcohol Isobutane Isobutyl acetate X A = Asphyxiant Heavier C5H8 Isoprene X 2.0 0.8 1.2 9 3.8 9.6 10.5 - - 150 Ca = Carcinogen -54 84 38 1.3 - 50 10 - 25 150 - 100 20 [C] 3 - 200 1,300 - 500 100 30 50 X X X X X X X X X X X X X X X X X X X - = Data not currently available - 5 [C] - - - 15 3 [C] 10 X 220 460 421 460 350 260 - 540 - 34 215 >160 118 -12 132 -60 20 26 -85 400 @ 15°C <1 2.3 14,060 760 Gas Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Heavier C9H14O Isophorone X 17 8.4 9 46 - 4.7 [C] 50 Catalytic 1.8 1.2 4.3 n/a - 5 [C] Photoacoustic IR Gas 43 Gas n/a 40 5 [C] Semiconductor Isopar G Isoparafﬁnic hydrocarbon X n/a 5.6 - Absorptive IR -18 n/a Autoignition Temp (°C)* D e t e c t i o n Heavier X Lighter HCN Hydrogen cyanide n/a Electrochemical n/a ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s X Heavier HCl Synonym Hydrogen chloride Hydrochloric acid Gas or Vapor Relative Density (vs.Air)+ Combustible Chemical Formula Gas Information Table M S A H a n d b o o k Fuel oil no. 1 Kerosene/JP-1 Jet fuel CH4O X A = Asphyxiant Heavier C3H6O2 Methyl acetate X 3.1 1.8 6.0 5.0 16 14 36 15 200 5 200 A - 250 50 400 250 Ca = Carcinogen -10 39 11 Gas 5 7.9 6.5 12.7 8 400 200 25 200 - - 500 50 400 250 400 3,100 200 6,000 A - 1,400 900 2,000 1,800 2,000 X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available 250 - 250 A - 310 - 500 310 500 Electrochemical Key: [C] = Ceiling Limit (never exceed) Heavier C3H8O2 X Heavier Methoxyethanol, Methyl cellosolve 2- Methyl alcohol Methanol X Lighter 0.7 1.4 0.9 2.0 1.8 12.7 X 454 285 464 537 210 443 425 399 460 399 60 124 64 -162 151301 69 152 83 90 83 3.2 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X X Thermal Conductivity CH4 37-72 -28 33 11 2 2.0 Autoignition Temp (°C)* D e t e c t i o n Methane X Heavier X C6H14O Diisopropyl ether Isopropyl ether Heavier C9H12 Cumene Isopropyl benzene X X Heavier C3H8O Isoproryl alcohol Isopropanol Heavier X Heavier C5H10O2 Isopropyl acetate Combustible 11 Catalytic Isoropyl alcohol Photoacoustic IR Isopropanol Absorptive IR X Relative Density (vs.Air)+ Semiconductor Heavier Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s C3H8O Gas or Vapor Gas Information Table M S A H a n d b o o k 61 62 Heavier Heavier Heavier C4H8O CH3F C2H4O2 Methyl ethyl ketone (MEK) Methyl ﬂuoride Methylformate A = Asphyxiant X X X X 5.0 1.4 7 8.1 1.8 1.2 10.0 23 11.4 16.0 17.4 14 8 16 100 200 350 50 5 5 1 Ca = Carcinogen -19 -9 -50 39 25 n/a 6,000 100 200 350 100 25 100 4,500 3,000 700 2,000 200 1,600 20 [C] 250 [Ca] 200 X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available 150 300 450 100 - 10 - 250 456 404 500 632 285 423 537 464 32 -78 80 74 -24 124 128 4 64 476 28,577 @ 21.1°C Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Butanone, 2 C2H3Cl3 Methylchloroform Trichloroethane, 1,1,1- X X X X 200 Autoignition Temp (°C)* D e t e c t i o n Heavier Heavier CH3Cl Chloromethane Methyl chloride Heavier Heavier C6H12O C3H8O2 Hexanone, 2- Heavier CH3Br 36 Electrochemical Methyl cellosolve 2methoxyethanol Bromomethane Methyl butyl ketone Combustible 6.0 Catalytic 11 Photoacoustic IR X Absorptive IR Methyl bromide Heavier CH4O Semiconductor Methanol Synonym Relative Density (vs.Air)+ Chemical Formula ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Methyl alcohol Gas or Vapor Gas Information Table M S A H a n d b o o k X Slightly heavier 4.9 1.3 20.7 9.6 23 20.7 5 10 50 5 50 50 25 50 Ca = Carcinogen Gas 29 13.0 4.9 8.2 8 5.5 8.2 10 75 25 10 100 100 25 100 100 X X X 2300 [Ca] 1,000 X X X X X X 100 1,000 - 400 - 100 [Ca] X X X X X X X X X X X X X X X X X X - = Data not currently available 15 - - 15 100 75 40 - 5 Electrochemical A = Asphyxiant X Heavier - Gas 1.7 1.2 1.0 1.0 - 430 638 556 430 435 448 - 191 - -6 132 40 -6 100 117 146 2,622 @ 25°C 12 350 2,622 @ 25°C 29 16 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) CH5N C6H5Cl (Benezene chloride) Mono chlorobenzene Monomethlamine Methylamine CH2Cl2 Dichloromethane Methylene chloride X X Slightly heavier CH5N Monomethylamine Methylamine 10 18 48 36 2 Autoignition Temp (°C)* D e t e c t i o n Heavier X Heavier C5H8O2 X X C6H12O Heavier X Methyl methacrylate C6H14O Heavier Combustible Methyl isobutyl ketone (MIBK) C7H14O Methyl isobutyl carbinol Methylamyl alcohol Methyl isoamyl ketone n/a Catalytic n/a Photoacoustic IR n/a Absorptive IR Heavier Relative Density (vs.Air)+ Semiconductor CH3I Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Methyl iodide Gas or Vapor Gas Information Table M S A H a n d b o o k 63 64 Heavier Same NO Nitric oxide Heavier Heavier Heavier NF3 C3H7NO2 C3H7NO2 N2O Nitrogen triﬂuoride Nitropropane, 1- Nitropropane, 2- A = Asphyxiant X X X 87 - n/a 2.2 2.2 n/a 1.8 - n/a 11 - n/a n/a - n/a - - 50 10 25 10 3 1 25 10 Ca = Carcinogen - 24 36 Gas n/a 6 5.9 - - - 25 25 10 5 [C] 1 25 10 100 - - 100 [Ca] 1,000 1,000 20 200 100 250 1,000 X X X X X X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - - - - 5 - - 15 428 421 480 526 -6 120132 120132 15 211 -52 2,052 @ 21.1°C 13 13 1,4 218 1.0 @ 53°C Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Octaﬂuorocyclobutane Octaﬂuorocyclopropene Nitrous oxide Heavier - NO2 n/a 0.9 0.9 Autoignition Temp (°C)* D e t e c t i o n C4F8 Heavier Heavier C6H5NO2 Nitrobenzene -2 79 Electrochemical Nitrogen dioxide X X Combustible Heavier Catalytic - Photoacoustic IR Coal Tar Absorptive IR Naphtha Semiconductor C10H8 Synonym Relative Density (vs.Air)+ Chemical Formula ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Napthalene Gas or Vapor Gas Information Table M S A H a n d b o o k - - A = Asphyxiant 2.5 2.1 18 9.5 98 n/a 0.5 2,500 0.3 0.1 - Ca = Carcinogen 21 Gas 1.6 n/a n/a 25 600 1,500 n/a 1,000 2 1,000 0 0 - 20 2,100 50 2 - 100 150 [Ca] 1,000 n/a 500 X X X X X X X X X X X X X X X X X X X X X X - = Data not currently available - - 1 - - 100 - n/a - 378 450 38 - - 260 206 97 -42 -88 8 >58 121 36 -183 126 17 >760 568 @ 0°C - 13 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) X Heavier C3H6O Propanol, 2- Allyl alcohol X Heavier C3H8 Propane Gas X Heavier PH3 n/a Heavier Phosphine Carbony chloride n/a n/a 7.8 n/a 300 Autoignition Temp (°C)* D e t e c t i o n Phosgene Perﬂuoromethyl- PMVE vinyl ether Perﬂuorohexane n/a 1.5 n/a 6.5 Semiconductor COCl2 n/a Heavier C2Cl4 Perchloroethlyene Tetrachloroethylene <-40 Heavier C5H12 Pentane - 1.0 Electrochemical X Gas Same 13 O2 Combustible X Catalytic Octane, n- Photoacoustic IR Oxygen Relative Density (vs.Air)+ Absorptive IR Heavier Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s CH8H18 Gas or Vapor Gas Information Table M S A H a n d b o o k 65 66 Heavier Heavier Heavier C3H6 C3H6Cl2 C3H6O Propylene Propylene dichloride Propylene oxide C8H8 X A = Asphyxiant Heavier X Heavier 1.1 0.9 1.4 2.1 3.2 2.0 2.2 7 6 96 37 14.5 11.7 13.7 8 20 100 - 2 75 A 200 200 Ca = Carcinogen 31 21 - -37 16 Gas 23 1.7 400 [Ca] - 800 1,700 100 500 - 700 2,000 mg/m3 - 100 400 [Ca] 75 - 200 200 800 X X X X X X X X X X X X X X X X X X X X - = Data not currently available 40 - - - 110 A 250 250 200 490 229 - 465 557 455 371 450 371 145 149204 -112 34 96 -47 97 102 97 5 442 40 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Styrene Stoddard solvent X Heavier X X 13 250 Electrochemical Silane Propyleneglycol dimethyl acetate SiH4 X Heavier C3H8O Propyl alcohol, n- Propanol, n X 200 Autoignition Temp (°C)* D e t e c t i o n Heavier X Heavier C5H10O2 Propyl acetate, n- 13.7 Catalytic 2.2 Photoacoustic IR 23 Absorptive IR X Heavier C3H8O Semiconductor Propyl alcohol, n- Synonym ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Propanol, n- Gas or Vapor Relative Density (vs.Air)+ Combustible Chemical Formula Gas Information Table M S A H a n d b o o k A = Asphyxiant 8.0 6.0 7 1/2 10.5 15.5 16.0 7.1 11.8 60 50 10 350 50 200 2 5 25 Ca = Carcinogen - 4 4 2.0 11.0 n/a n/a 100 10 350 200 200 - 10 X 1,000 [Ca] X X X X X 100 [Ca] 700 500 2,000 - 200 100 150 [Ca] - 100 X X X X X X X X X X X X X X X X X X - = Data not currently available 100 - 450 - 250 - 10 100 1,000 5 420 - 500 480 321 188 - - - 87 113 74 111 66 -78 77 121 -10 58 19 100 22 145 91 13 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X Thermal Conductivity Key: [C] = Ceiling Limit (never exceed) Heavier C2HCl3 Trichloroethylene X X Heavier C2H3Cl3 X Heavier C7H8 Toluene X X Heavier C4H8O Tetrahydrofuran Heavier <0 X Heavier C2F4 Tetraﬂuoroethylene n/a n/a - 5 Catalytic C2H3Cl3 n/a Heavier CCl4 Tetrachloromethane Carbon Tetrachloride 1,000 2 Autoignition Temp (°C)* D e t e c t i o n Trichloroethane, Methyl chloroform 1, 1, 1Trichloroethane, 1, 2, 2- n/a Heavier C2Cl4 Tetrachloroethylene Perchloroethylene n/a n/a Photoacoustic IR n/a n/a Semiconductor -14 n/a Heavier Gas SF6 Combustible SO2 Electrochemical Heavier Relative Density (vs.Air)+ Absorptive IR Sulfur hexaﬂuoride Synonym Chemical Formula ACGIHT ACGIHT OSHA NIOSH Flash LEL UEL LVLV IDLH Point (% by (% by TWA -STEL PEL (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s Sulfur dioxide Gas or Vapor Gas Information Table M S A H a n d b o o k 67 68 Heavier - Heavier Heavier Heavier Heavier Heavier C6H15N C10H16 C4H6O2 C2H3Cl C2H3F C2H2Cl2 C8H10 Triethylamine Turpentine Vinyl acetate Vinyl chloride Vinyl ﬂuoride Vinylidene chloride Xylenes X X X X X X 1.1 7.3 2.6 3.6 2.6 0.8 6.7 16 21.7 33 13.4 - 100 5 - 1 10 100 1 100 - - 1 - 100 25 900 Ca - Ca - 800 200 Electrochemical X X X X X X X X X X X X X X X X X X X - = Data not currently available 150 - - - 15 - 3 500 32 -72 -14 73 149 89 62 463-528 137144 570 385 472 402 220 249 - 400 @ 15°C 25.2 atm 2,524 88 54 160 Vapor Boil- Pressure ing (mm Point Hg at (°C)1 20°C) 1,4 n/a = Data not applicable X X X X X X X Thermal Conductivity Ca = Carcinogen 27-30 -18 Gas -78 -6 35 8 50 [C] Catalytic 1.2 - Semiconductor -9 10 Autoignition Temp (°C)* D e t e c t i o n Key: [C] = Ceiling Limit (never exceed) Combustible X n/a Photoacoustic IR n/a Absorptive IR n/a ACGIHT ACGIHT LVLV Flash LEL UEL OSHA NIOSH Point (% by (% by TWA -STEL PEL IDLH (°C)1* vol)1 vol)1 (PPM)2 (PPM)2 (PPM)3 (PPM)4 Detection Technologies G a s A = Asphyxiant Heavier CHCl3 Synonym Trichloromethane Chloroform Gas or Vapor Relative Density (vs.Air)+ Chemical Formula Gas Information Table M S A H a n d b o o k M S A G a s D e t e c t i o n H a n d b o o k GAS INFORMATION TABLE 1 Data obtained from the National Fire Protection Association (NFPA) Fire Protection Guide to Hazardous Materials, 13th ed., 2002, National Institute for Occupational Safety and Health (NIOSH) Pocket Guide to Chemical Hazards, 1995, and material safety data sheets. 2 Data obtained from American Conference of Governmental Industrial Hygienists (ACGIH) 2002 Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs), and material safety data sheets. 3 The PELs are the maximum 8-hour time weighted average concentrations to which a worker may be exposed, per 29 CFR 1910.1000 Table Z-1; [C] denotes a ceiling limit, the maximum concentration to which a worker may be exposed. They are to be determined from breathing-zone air samples. Data obtained from National Institute for Occupational Safety and Health (NIOSH) Documentation for Immediately Dangerous to Life or Health Concentrations, 1995, and material safety data sheets. 4 Data obtained from U.S. Department of Labor Occupational Safety and Health Administration (OSHA) 29 CFR 1910.1000 Table Z-1 Limits for Air Contaminants, and material safety data sheets. ^ See 29 CFR 1910.1028 for speciﬁc circumstantial exceptions. + Density of gas at 1 atmosphere. * ‘Gas’ indicates substance is a gas at normal ambient temperature. 69 Section 4 A Selection of Gases Typically Associated with Various Industries M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Launch pads X Heat treating Combustible Gases Plant facilities Industry Test cambers/labs Aerospace/Defense X X X Ammonia X Carbon dioxide X X Carbon monoxide X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide X Nitrogen dioxide O2 deﬁciency/enrichment X X Refrigerants X X Toluene X X X Phosphine VOC’s 72 X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia X X Carbon dioxide X X Carbon monoxide X X Soil fertilization X X X Livestock, oil extraction process Fumigation X Poultry houses X Grain storage & processing Conﬁned spaces (silos) Combustible Gases Forklift operation Greenhouses, silos & storage areas Chillers Industry Fruit storage areas Agriculture X X X X X X Chlorine Chlorine dioxide Ethylene X X X Ethylene oxide X Hydrogen chloride Hydrogen cyanide X Hydrogen sulﬁde X Nitric oxide X X Nitrogen dioxide X X O2 deﬁciency/enrichment X Phosphine Refrigerants X X X X X Sulfar Dioxide VOC’s X X X X 73 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Research & development labs Engine testing Environmental chambers Automotive X X X Carbon dioxide X X X Carbon monoxide X X X Industry Combustible Gases Ammonia Chlorine Chlorine dioxide Ethylene Ethylene oxide X Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide X X Nitrogen dioxide X X O2 deﬁciency/enrichment X X X Refrigerants X X X Sulfur dioxide X VOC’s X Phosphine 74 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries X X X Aircraft parts mfg. Jet fuel vapors, solvents X Conﬁned space (wing) tank maintenance Combustible Gases Aircraft hanger facilities, fuel & hydraulic ﬂuid storage and pumping facilities Industry Body & engine repair & maintenance Aviation Ammonia Carbon dioxide Carbon monoxide X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide X X Hydrogen sulﬁde Nitric oxide X Nitrogen dioxide X X O2 deﬁciency/enrichment X X Phosphine Refrigerants Sulfur dioxide VOC’s X X X X 75 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Manufacturing, polymers/plastics, process manufacturing for leaks Organic synthesis operations, liquid-solid separation, cleaning agents General leak detection, organic synthesis X X X X X X X X X X X X X X X X X X X Ethylene X X X X X Ethylene oxide X X X X X Hydrogen chloride X Hydrogen cyanide X Hydrogen sulﬁde X Nitric oxide X X Nitrogen dioxide X X O2 deﬁciency/enrichment X Phosphine X Combustible Gases X Ammonia X Carbon dioxide X X Carbon monoxide X X Chlorine X Chlorine dioxide Industry Refrigerants X X X X X X X X X X X X X X X X X X X X X Sulfur dioxide X VOC’s X 76 Textiles Labs, ﬁne chemical manufacturing X General leak detection process manufacturing Conﬁned space (liquid nitrogen carriers/storage tank maintenance, reactor work, tunnels) Chemical X X X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Rubber Storage warehouses Solvent recovery Holding tanks, transfer areas, loading & unloading areas Chemical Combustible Gases X X X X Ammonia X X X Carbon dioxide X X Carbon monoxide X X Chlorine X X Chlorine dioxide X X Ethylene X X Ethylene oxide X Hydrogen chloride X Industry Hydrogen cyanide X X Hydrogen sulﬁde X X Nitric oxide X Nitrogen dioxide X O2 deﬁciency/enrichment X Phosphine X Refrigerants X Sulfar Dioxide X VOC’s X X X X X 77 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases Press processes Industry Manufacturing ﬂoor, outside of press Coatings & Printing Adhesives X X X X X X Ammonia Carbon dioxide Carbon monoxide Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment Phosphine Refrigerants Sulfar Dioxide VOC’s 78 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia X X X Carbon dioxide X X X Carbon monoxide X Coolers, conﬁned spaces X Heaters & boilers, gasolinepowered equipment, vehicles & forklifts baking facilities X Breweries & wineries, beverage bottling, fermentation tanks, refrigeration facilities, meat packing, food processing Edible oil processing Combustible Gases Grain processing Fruit storage areas Industry Refrigeration facilities & cold storage Food & Beverage X X X X X Chlorine Chlorine dioxide Ethylene X X Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide X Nitrogen dioxide X O2 deﬁciency/enrichment X X Refrigerants X X Sulfur dioxide X X Phosphine X X X X VOC’s 79 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases Ammonia X Carbon dioxide X Carbon monoxide X Disinfecting equipment & utensils X Fumigation of yeast & mold spores, sterilization X Fermentation process, packaging or gassing foods, conﬁned space Drainage & sewage areas, boilers & heaters, food packaging Industry Wastewater tanks, drainage & sewage areas Food & Beverage X X Chlorine X X Chlorine dioxide X X X X Ethylene X Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde X X Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X Phosphine Refrigerants Sulfur dioxide VOC’s 80 X X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases Food packaging (solvent vapor process monitoring) Industry Cold storage & transport facilities, meat packing plants, supermarkets, refrigerator & storage locations, food storage systems monitoring Food & Beverage X Ammonia X Carbon dioxide X Carbon monoxide X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X Phosphine Refrigerants X Sulfur dioxide X VOC’s X 81 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Coremaking Heat-treating processes Conﬁned space Manufacturing ﬂoor, fuel cells Combustible Gases Fuel cell Manufacturing Metal-mining, ﬁnishing work Industry Furnace operation, coremaking, metal preparation & pouring Foundries X X X X X Ammonia Carbon dioxide Carbon monoxide X X X X X X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide X Hydrogen sulﬁde X X Nitric oxide X Nitrogen dioxide X O2 deﬁciency/enrichment X Phosphine Refrigerants Sulfur dioxide VOC’s 82 X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries X X Ammonia X Carbon dioxide Carbon monoxide X Chlorine X Chlorine dioxide X Storage, transfer and treatment X Underground construciton X Combustible Gases Conﬁned space Flammable liquid/ gas storage & pumping facilities Industry HazMat applications HAZMAT X X X X X X X X Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde X Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment Phosphine X Refrigerants Sulfur dioxide X VOC’s X X X X 83 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia Forklift & crane operations X X X Carbon dioxide Carbon monoxide Metal-plating Vehicle emissions X Manufacturing process emissions Combustible Gases Heat-transfer ﬂuids Industry Vehicle manufacturing plants Heavy Manufacturing X X X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride X Hydrogen cyanide X Hydrogen sulﬁde X Nitric oxide Nitrogen dioxide X X X X X X X X X O2 deﬁciency/enrichment Phosphine Refrigerants X X Sulfur dioxide VOC’s 84 X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia X Mechanical equipment rooms X Degreasers Combustible Gases Paint booths Industry Chemical loading/ off-loading Heavy Manufacturing X X X X Carbon dioxide Carbon monoxide Chlorine X X Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X Phosphine Refrigerants X Sulfur dioxide VOC’s X X X 85 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries X Carbon dioxide X Carbon monoxide X X X X X X X X X X X Mechanical rooms X Cold storage & transport facilities, meat packing plants, supermarkets, refrigerator storage locations, food storage system monitoring Ventilation ducts Ammonia Parking garages, tunnels, furnace rooms, maintenance garages X Occupied buildings, ofﬁce buildings, research labs Combustible Gases Parking garages, warehouses Industry Heating boilers or ducting, general ofﬁce applications HVAC X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide X X Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X X X X X X X X X X Phosphine Refrigerants Sulfur dioxide VOC’s 86 X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases Parking garages, tunnels, furnace rooms, maintenance garages, crawl spaces Industry Occupied buildings (industrial, commercial, residential), ofﬁce buildings, research labs Indoor air quality X X Carbon dioxide X X Carbon monoxide X X Ammonia Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X X X X Phosphine Refrigerants Sulfur dioxide VOC’s X 87 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia X Carbon dioxide X Carbon monoxide X X X X Motor maintenance & cleaning, coke oven emissions X Maintenance rooms (chillers) Conﬁned space X Welding X Coking operations Combustible Gases Metal-mining, ﬁnishing work, fuel storage Industry Blast furnance operation & maintenance, converter operation, furnace & gas pipeline leaks Iron & Steel X X X X X X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde X Nitric oxide X Nitrogen dioxide X O2 deﬁciency/enrichment X X X Phosphine Refrigerants Sulfur dioxide VOC’s 88 X X X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Mechanical equipment rooms Decontamination areas Parking garages MRI Central supply, sterilization areas Alcohol’s, “sick building syndrome” Industry Operating rooms, occupied areas Medical Combustible Gases X Ammonia X Carbon dioxide X X Carbon monoxide X X Chlorine Chlorine dioxide Ethylene X X Ethylene oxide X X X Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X Phosphine Refrigerants X Sulfur dioxide VOC’s X X X 89 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries X X Ammonia Diesel-powered machinery, blasting X Diesel exhaust Result of combustion (ﬁre), diesel-powered machinery exhaust, conﬁned space blasting X Metal mining Mining process Combustible Gases Mechanized coal cutting Industry Conﬁned space Mining X X X X X X X Carbon dioxide X Carbon monoxide X X X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide X Hydrogen sulﬁde X X Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X X Phosphine Refrigerants Sulfur dioxide VOC’s 90 X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases X Ammonia X X X X X Conversion processes, isomerization, catalytic reforming, treatment processes, leak detection, storage vessels, perimeter monitoring Incomplete combustion, conversion, coking, general processing, leak detection Reﬁneries, petrochemical facilities, perimeter monitoring Reﬁneries Pipeline compressor stations & pumping stations Industry Petroleum reﬁning Oil & Gas X X Carbon dioxide Carbon monoxide X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride X X X X X Hydrogen cyanide Hydrogen sulﬁde X X X Nitric oxide Nitrogen dioxide X O2 deﬁciency/enrichment X Phosphine Refrigerants Sulfur dioxide X X X VOC’s X X X X 91 92 Carbon dioxide Hydrogen sulﬁde Offshore drilling platformsstorage & processing areas, control rooms, living spaces, power generation rooms Reﬁning process, process stream sample collection, general plant operations Mechanical equipment rooms Thermal oxidizers Combustible Gases Natural gas lines Industry Conﬁned space (tank cleaning operations, enclosed bldgs or structures) G a s Reﬁning process, general leak detection, treatment processes, crude separation, drilling rigs M S A D e t e c t i o n X O2 deﬁciency/enrichment Sulfur dioxide X VOC’s X X X H a n d b o o k A Selection of Gases Typically Associated with Various Industries Oil & Gas X X X X X X X Ammonia X X Carbon monoxide Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide X X Nitric oxide Nitrogen dioxide X Phosphine Refrigerants X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia Paper production (coating & dying) Mechanical equipment rooms Combustible Gases Conﬁned spaces (tanks, pits, sumps, vats) Chemical pulping, Kraft pulping Industry Paper production (bleaching) Paper & Pulp X X X X X Carbon dioxide Carbon monoxide Chlorine X Chlorine dioxide X X Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde X X X Nitric oxide Nitrogen dioxide X X O2 deﬁciency/enrichment X Phosphine Refrigerants X Sulfur dioxide X VOC’s X X X 93 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Manufacturing, gas leaks Solvent vapor process monitoring Chemical synthesis operations Labs, ﬁne chemical manufacturing Labs, organic synthesis, liquidsolid separation, compounding, granulating & tablet-coating operations, drying & packaging, ﬁne chemical manufacturing Pharmaceutical Combustible Gases X X X X X Ammonia X X X X X Industry Carbon dioxide X X Carbon monoxide X Chlorine X Chlorine dioxide X Ethylene Ethylene oxide X X X X X X X X X X X Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X Phosphine Refrigerants Sulfur dioxide VOC’s 94 X X X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases Utilities Compressed breathing air Industry Nitrogen blanketing of storage vessels, reactors and centrifuges Pharmaceutical X Ammonia Carbon dioxide Carbon monoxide X X X X X X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment Phosphine Refrigerants X Sulfur dioxide VOC’s 95 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Fuel transportL loading & unloading Fossil fuel power plants Conﬁned space X X X X X Ammonia X Carbon dioxide X Carbon monoxide X X Chlorine X X X Coal & fuel oil oxidization in combustion process (emissions) Fuel storage X Power generation plants Combustible Gases Transformer insulation Industry Home furnace leaks Power generation X X X X X X Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride X X Hydrogen cyanide Hydrogen sulﬁde Nitric oxide X Nitrogen dioxide X O2 deﬁciency/enrichment X X X X Phosphine Refrigerants Sulfur dioxide Sulfur hexaﬂuoride VOC’s 96 X X X X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases X Compressed breathing air Chiller plant Lithography, etching, oxidation, metalization, assembly & testing Cleaning agents, ﬂuorinated compounds As doping agent in manufacturing, diffusion and ion implementation, checmcal vapor deposition Industry Manufacturing, processing Semiconductor fabs X Ammonia X Arsine X Bromine X Carbon monoxide X Chlorine X Chlorine dioxide X Diborane X Germane X Hydrogen chloride X X X Hydrogen cyanide Nitric oxide X Nitrogen dioxide X O2 deﬁciency/enrichment X Phosphine X Refrigerants Silane VOC’s X X X X X 97 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Ammonia X Carbon dioxide Carbon monoxide X Ferry boats X U.S. Navy ships X Oil tanker pumps X LNG transport Waste treatment X Chillers Engine room Combustible Gases Fuel storage & pumping facilities Industry Conﬁned space (storage holds) Shipyard/marine X X X X X X X X X X X Chlorine Chlorine dioxide X Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde X X Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X X Phosphine Refrigerants X X X Sulfur dioxide VOC’s 98 X X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries General processes Sewer work Conﬁned space X X X X X X X Ammonia X Carbon dioxide Pump stations Plant pumps, plant sewage basin monitoring for solvent leaks or dumping X Wet well inﬂuent Stagnant gas, incinerators X Combustible Gases Dechlorinization, storage tanks Digesters, digester gas storage Industry Processing; storage tanks, rooms & pipes Water & Wastewater X X X X X X X Carbon monoxide Chlorine X X X Chlorine dioxide X X X Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde X X X X X X X X Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment X Phosphine Refrigerants Sulfur dioxide VOC’s X X X 99 M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases X Ammonia X Carbon dioxide X Carbon monoxide X Thermite and stud welding, laser welding & chilling, arc air cutting, arc welding, electric resistance & gas pressure welding, metal cutting & ﬂame gouging, brazing General operations Industry Conﬁned space, arc air cutting, ﬂuxshielded & gas shielded arc welding, metal cutting & ﬂame gouging, gas pressure welding Welding X X Chlorine Chlorine dioxide Ethylene X Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide O2 deﬁciency/enrichment Phosphine Refrigerants Sulfur dioxide VOC’s 100 X X M S A G a s D e t e c t i o n H a n d b o o k A Selection of Gases Typically Associated with Various Industries Combustible Gases Conﬁned space welding, electron beam welding Industry Arc welding & cutting, stud welding, arc + air cutting, gas pressure welding, metal cutting & ﬂame gouging Welding X X Ammonia Carbon dioxide Carbon monoxide X Chlorine Chlorine dioxide Ethylene Ethylene oxide Hydrogen chloride Hydrogen cyanide Hydrogen sulﬁde Nitric oxide Nitrogen dioxide X O2 deﬁciency/enrichment X X Phosphine Refrigerants Sulfur dioxide VOC’s 101 Section 5 Hazardous Locations Classification Class I: Flammable Gasses, Vapors or Liquids Class II: Combustible Dusts Class III Ignitable Fibers & Flyings ATEX - Explosive Atmospheres A Selection of Recognized Testing Laboratories System Installation M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification The hazardous location classiﬁcation system was designed to promote the safe use of electrical equipment in environments deﬁned as “hazardous areas”. A hazardous area is a location in which the potential presence of a ﬂammable gas/ air mixture requires special precautions to reduce the possibility of any electronics in the hazardous area becoming a source of ignition. In the gas detection applications, hazardous areas are generally deﬁned by two factors: the type of gas that may be present, and the degree of probability that it will be present at any given instant. Hazardous areas are deﬁned slightly differently in various countries, but essentially the same result is achieved. Areas are classiﬁed according to the likelihood that they will produce a combustion hazard for the electronic device. In a hazardous area each apparatus must possess the appropriate approvals for safe operation in that area (i.e., to ensure that it does not become a source of ignition). Various methods of protection are used to meet this need. Area Classification Each area is classiﬁed according to the likelihood that the hazard will be present at any given instant. There are two major hazardous location classiﬁcations: • Classiﬁcation 1: Used in North American installations (US National Electric Code“ and Canadian Electric Code). Areas are subdivided into “Classes” and “Divisions”. • Classiﬁcation 2: Used in European (CENEL EC) and International Electrotechnical Committee- (IEC) aligned countries such as Australia; also used in some North American installations. Areas are categorized into “Zones”. Gas Groups Gases are grouped according to their ignition energies which are produced from spark sources (from most easily ignited to least easily ignited). 104 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Temperature Class Gases are also grouped according to their ignition temperature. This is the maximum surface temperature that can be attained by an apparatus or component at maximum-rated ambient temperature. Six basic temperature classes are used to categorize this factor (T1 through T6). The higher the temperature class, the lower the maximum surface temperature and thus the wider the range of gases for which the apparatus is suitable. Protection Methods Various forms of ignition protection are used, such as intrinsic safety, explosionproof, ﬂameproof, purging/ pressurization, hermetic sealing and non-sparking design. Environmental Protection Environmental protection refers to design methods used to minimize equipment exposure to invasive environmental conditions such as water, ice, dust and corrosion. As with Hazardous Area Classiﬁcations, equipment environmental protection ratings vary somewhat within and outside of North America. As seen in the following two tables, National Electrical Manufacturers Association (NEMA) and Ingress Protection (IP) Codes provide similar information regarding instrument protection against various environmental conditions. Attaining one rating does not imply that the other ratings have also been met. 105 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification INGRESS PROTECTION (IP) CODES (IEC/EN 60529) FIRST NUMERAL Protection against solid bodies SECOND NUMERAL Protection against liquids No Protection 0 0 No Protection Objects Greater Than 50mm 1 1 Vertically Dripping Water Objects Greater Than 12mm 2 2 Angled Dripping Water - 75° to 90° Objects Greater Than 2.5mm 3 3 Sprayed Water Objects Greater Than 1.0mm 4 4 Splashed Water Dust-Protected 5 5 Water Jets Dust-Tight 6 6 Heavy Seas 7 Effects of Immersion 8 Indefinite Immersion Example: IP65 equipment is dust-tight and protected against water jets 106 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Enclosure Ratings NEMA, UL, & Approximate CSA Type Rating IEC/IP classification Abbreviated protection description 1 IP30 Indoor, from contact with contents 2 IP31 Indoor, limited, from dirt & water 3 IP64 Outdoor, from rain, sleet, windblown dust & ice damage 3R IP32 Outdoor, from rain, sleet & ice damage 4 IP66 Indoor & outdoor, from windblown dust, rain, splashing & hose directed water & ice damage 4X IP66 Indoor & outdoor, from corrosion, windblown dust, rain, splashing & hose directed water & ice damage 6 IP67 Indoor & outdoor, from hose-directed water, water entry during submersion & ice damage 12 IP55 Indoor, from dust, falling dirt & dripping non-corrosive liquids 13 IP65 Indoor, from dust, spraying water, oil & non-corrosive liquids 107 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class I: Flammable Gases, Vapors or Liquids Class I Area Classification Division 1: Where ignitable concentrations of ﬂammable gases, vapors or liquids can exist all of the time or some of the time under normal operating conditions. Division 2: Where ignitable concentrations of ﬂammable gases, vapors or liquids are not likely to exist under normal operating conditions. Zone 0: Where ignitable concentrations of ﬂammable gases, vapors or liquids are present continuously or for long periods of time under normal operating conditions. Zone 1: Where ignitable concentrations of ﬂammable gases, vapors or liquids are likely to exist under normal operating conditions. Zone 2: Where ignitable concentrations of ﬂammable gases, vapors or liquids are not likely to exist under normal operating conditions. Class I Groups Division 1 and 2 A acetylene B hydrogen, fuel and combustible process gases containing more than 30% hydrogen by volume, or gases or vapors of equivalent hazard such as butadiene, ethylene oxide, propylene oxide and acrolein C cyclopropane, ethyl ether, ethylene, or gases or vapors of equivalent hazard D acetone, ammonia, benzene, butane, ethanol, gasoline, hexane, methane, natural gas, naptha, propane, or gases or vapors of equivalent hazard Zone 0, 1 and 2 IIC acetylene and hydrogen, fuel and combustible process gases containing more than 30% hydrogen by volume, or gases or vapors of equivalent hazard such as butadiene, ethylene oxide, propylene oxide and acrolein IIB cyclopropane, ethyl ether, ethylene, or gases or vapors of equivalent hazard IIA acetone, ammonia, benzene, butane, ethanol, gasoline, hexane, methane, natural gas, naptha, propane, or gases or vapors of equivalent hazard 108 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class I: Flammable Gases, Vapors or Liquids Class I Temperature Codes (Maximum surface temperature of apparatus) Division 1 and 2 Zone 0, 1, and 2 T1 (≤450°C) T1 (≤450°C) T2 (≤300°C) T2 (≤300°C) T2A, T2B,T2C,T2D (≤280°C, ≤260°C, ≤230°C, ≤215°C) - T3 (≤200°C) T3 (≤200°C) T3A, T3B, T3C (≤180°C, ≤165°C, ≤160°C) - T4 (≤135°C) T4A (≤120°C) T4 (≤135°C) T5 (≤100°C) T5 (≤100°C) T6 (≤85°C) T6 (≤85°C) 109 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class I: Flammable Gases, Vapors or Liquids Class I, Division 1 and 2 Protection Methods Applicable Certification Documents Area Protection Methods • Explosionproof Div. 1 • Intrinsic safety (2 fault) UL 1203 CSA-30 UL 913 CSA-157 NFPA 496 • Hermetically sealed UL 1604 CSA-213 • Nonincendive UL 1604 CSA-213 • Non-Sparking UL 1604 CSA-213 NFPA 496 NFPA 496 — — UL 2279 CSA-E79 Series • Purged/Pressurized (Type Z) • Any Class I, Div. 1 method • Any Class I, Zone 0, 1 or 2 method 110 Canada NFPA 496 • Purged/pressurized (Type X or Y) Div. 2 USA M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class I: Flammable Gases, Vapors or Liquids Class I, Zone 0, 1 and 2 Protection Methods Applicable Certification Documents IECEx Scheme† Europe E60079-11 IEC 60079-11 EN 60079-11 No IEC 60079-26 EN 60079-26 UL 60079-18 CSA-E79-18 IEC 60079-18 EN 60079-18 UL 60079-1 E60079-1 IEC 60079-1 EN 60079-1 • Increased safety, ‘e’ UL 60079-7 E60079-7 IEC 60079-7 EN 60079-7 • Intrinsic safety, ‘ib’ (1 fault) E60079-11 IEC 60079-11 EN 60079-11 • Oil immersion, ‘o’ UL 60079-11 UL 60079-6 E60079-6 IEC 60079-6 EN 50015 • Powder ﬁlling, ‘q’ UL 60079-5 E60079-5 IEC 60079-5 EN 50017 • Pressurization, ‘px’ or ‘py’ ISA 12.04.01 E60079-2 IEC 60079-2 EN 60079-2 Protection Methods USA • Intrinsic safety, 'ia' (2 fault) UL 60079-11 • Special requirements Pending • Encapsulation, ‘m’ • Flameproof, ‘d’ Canada Zone 2 Zone 1 Zone 0 Area • Any Class I, Zone 0 Yes Yes Yes Yes • Any Class I, Div. 1 Yes Yes No No • Non-sparking, 'nA' UL 60079-15 E60079-15 IEC 60079-15 EN 60079-15 • Enclosed break, 'nC' UL 60079-15 E60079-15 IEC 60079-15 EN 60079-15 • Energy limited, 'nL' UL 60079-15 E60079-15 IEC 60079-15 EN 60079-15 • Restricted breathing, 'nR' UL 60079-15 E60079-15 IEC 60079-15 EN 60079-15 • Pressurization, 'pz' ISA 12.04.01* E60079-2 IEC 60079-2 EN 60079-2 • Any Class I, Zone 0 or 1 method Yes Yes Yes Yes • Any Class I, Div. 1 or 2 method Yes Yes No No Note: 60079-0 General requirements used in conjunction with 60079-xx. UL 60079-xx equivalents are available as ANSI/ISA 60079-xx. Note 2: UL 60079-xx equivalents are available as ANSI/ISA 60079-xx. Note 3: Requirements subject to change without notice. Check your local authorithy having jurisdiction for current requirements. * See NFPA 496 for Type X, Y, and Z. 111 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class II: Combustible Dusts Class II Area Classification Division 1: Where ignitable concentrations of combustible dusts can exist all of the time or some of the time under normal operating conditions. Division 2: Where ignitable concentrations of combustible dusts are not likely to exist under normal operating conditions. Class II Groups Division 1 and 2 E (metals – Div. 1 only) F (coal) G (grain) Class II Temperature Codes Division 1 and 2 T1 (≤450°C) T2 (≤300°C) T2A, T2B,T2C,T2D (≤280°C, ≤260°C, ≤230°C, ≤215°C) T3 (≤200°C) T3A, T3B, T3C (≤180°C, ≤165°C, ≤160°C) T4 (≤135°C) T4A (≤120°C) T5 (≤100°C) T6 (≤85°C) 112 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class II: Combustible Dusts Class II, Division 1 and 2 Protection Methods Applicable Certification Documents Area Protection Methods • Dust-ignitionproof Div. 1 • Intrinsic safety • Pressurized Div. 2 USA Canada UL 1203 CSA-25 or CSA-E1241-1-1 UL 913 CSA-157 NFPA 496 NFPA 496 • Dusttight UL 1604 CSA-157 or CSA-E1241-1-1 • Hermetically sealed UL 1604 — • Nonincendive UL 1604 — NFPA 496 NFPA 496 — — • Pressurized • Any class II, Div. 1 method 113 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Hazardous Locations Markings Class I, II & III, Division 1 & 2 (USA & Canada) – This marking would include: Class(es), Division(s), Gas/Dust Group(s), Temperature Code Example: Class I, Division 1, Group C & D, T4A Class I, Zone 0, 1 & 2 (USA) – This marking would include: For Zone Listings based on 60079-xx Class, Zone, AEx, Protection Method(s), Gas Group, Temperature Code Example: Class I, Zone 1, AEx de IIB T4 Class I, Zone 0, 1 & 2 (Canada) – This marking would include: For Zone Listings based on Canadian Zone Certiﬁcation Documents Class, Zone, Ex, Protection Method(s), Gas Group, Temperature Code Example:Class I, Zone 1, Ex de IIB T4 Zone 0, 1 & 2 (IECEx Scheme) – This marking would include: Ex, Protection Method(s), Gas Group, Temperature Code Example: Ex de IIB T4 Zone 0, 1 & 2 (Europe) – This marking would include: EEx, Protection Method(s), Gas Group, Temperature Code Example: Ex de IIB T4 ATEX Directive (Europe) – In addition to the European Ex marking string noted above, this marking would include: Non-mining: CE, Notiﬁed Body (NB) Identiﬁer, , Equipment Group & Category, G (gas)/D (dust) Example: (for DEMKO): 0539 II 2 Mining: 114 CE, Notiﬁed Body (NB) Identiﬁer, , Equipment Group & Category Example: (for DEMKO): 0539 I2 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class III: Ignitable Fibers & Flyings Class III Area Classification Division 1: Where easily ignitable ﬁbers or materials producing combustible ﬂyings are handled, manufactured or used. Division 2: Where easily ignitable ﬁbers are stored or handled. Class III Groups Division 1 and 2 None Class III Temperature Codes Division 1 and 2 None Note: Article 503 of the NEC limits the maximum temperature for Class III equipment to 165ºC for equipment not subject to overloading and to 120ºC for equipment that may be overloaded. 115 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification Class III: Ignitable Fibers & Flyings Class III, Division 1 and 2 Protection Methods Applicable Certification Documents Area Protection Methods • Dusttight Div. 1 • Hermetically sealed • Intrinsic safety • Nonincendive Div. 2 116 • Any Class III, Div. 1 method USA Canada UL 1604 UL 1604 UL 913 CSA--157 — CSA-157 UL 1604 — — M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification UL’s Hazardous Locations Standards UL 515 Electrical Resistance Heat Tracing for Commercial and Industrial Applications ANSI/UL 583 Electric-Battery-Powered Industrial Trucks ANSI/UL 674 Electric Motors and Generators for Use in Division 1 Hazardous (Classiﬁed) Locations ANSI/UL 698 Industrial Control Equipment for Use in Hazardous (Classiﬁed) Locations ANSI/UL 698A Industrial Control Panels Relating to Hazardous (Classiﬁed) Locations ANSI/UL 781 Portable Electric Lighting Units for Use in Hazardous (Classiﬁed) Locations ANSI/UL 783 Electric Flashlights and Lanterns for Use in Hazardous (Classiﬁed) Locations ANSI/UL 823 Electric Heaters for Use in Hazardous (Classiﬁed) Locations ANSI/UL 844 Electric Lighting Fixtures for Use in Hazardous (Classiﬁed) Locations ANSI/UL 877 Circuit Breakers and Circuit-Breaker Enclosures for Use in Hazardous (Classiﬁed) Locations ANSI/UL 886 Outlet Boxes and Fittings for Use in Hazardous (Classiﬁed) Locations ANSI/UL 894 Switches for Use in Hazardous (Classiﬁed) Locations ANSI/UL 913 Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division I, Hazardous (Classiﬁed) Locations 117 M S A G a s D e t e c t i o n H a n d b o o k Hazardous Locations Classification UL’s Hazardous Locations Standards ANSI/UL 1002 Electrically Operated Valves for Use in Hazardous (Classiﬁed) Locations ANSI/UL 1010 Receptacle-Plug Combinations for Use in Hazardous (Classiﬁed) Locations ANSI/UL 1067 Electrically Conductive Equipment and Materials for Use in Flammable Anesthetizing Locations ANSI/UL 1203 Explosionproof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classiﬁed) Locations ANSI/UL 1207 Sewage Pumps for Use in Hazardous (Classiﬁed) Locations UL 1604 ANSI/UL 2208 UL 2225 ANSI/UL 2279 118 Electrical Equipment for Use in Class I and II, Division 2, and Class III Hazardous (Classiﬁed) Locations Solvent Distillation Units Metal-Clad Cables and Cable-Sealing Fittings for Use in Hazardous (Classiﬁed) Locations Electrical Equipment for Use in Class I, Zone 0, 1 and 2 Hazardous (Classiﬁed) Locations M S A G a s D e t e c t i o n H a n d b o o k CE Approval CE is a labeling system required by some European countries to identify those products which are permitted to be sold in EU (European Union) member states. CE approval is used to verify compliance with certain European health and safety rules known as “Directives”. The Directives relevant to permanent gas detection instrumentation are the Electromagnetic Compatibility (EMC) Directive, Low Voltage Directive and ATEX Directive. EMC Directive The Electromagnetic Compatibility Directive 89/336/EEC is designed to limit the effects that one piece of equipment may have on another piece of equipment due to the electrical interference it produces. The effects of such interference can be severe enough to cause a device to shut down when another one is switched on. Electrical signals called EMI (Electromagnetic Interference) are the main cause of these effects. Most of the interference is in the form of radio waves (electromagnetic radiation, also called “emissions”) that are produced inside electrical equipment as a result of high speed communications involving the switching of high speed currents. The EMC Directive requires that equipment emissions be minimized and that the device be rendered immune to the emissions of other equipment. This is accomplished by designing the unit to meet the requirements set forth in European standard EN 50270, which sets limits on the amount of emissions permitted and susceptibility levels (immunity) for equipment. Electrostatic Discharge (ESD), another form of electrical interference that can disrupt equipment functions, is also addressed in EN 50270. Low Voltage Directive The Low Voltage Directive (LVD) is a European personal safety Directive that is comparable to a US/Canadian ﬁre/shock and safety approval. It applies to AC line powered devices and high voltage DC equipment. Speciﬁcally, the Directive applies to any equipment powered from a 50 VAC or 75 VDC or higher power source. The standard used for designing to compliance is EN/IEC 61010. 119 M S A G a s D e t e c t i o n H a n d b o o k ATEX – Explosive Atmospheres ATEX is the term used for the European Union’s Directive 94/9/EC which concerns equipment and protective systems intended for use in potentially explosive atmospheres. The purpose of the directive is to facilitate trade within the EU by aligning the laws of the Member States in Europe regarding safety requirements for hazardous area products. ATEX approval requires that the following issues be met: 1. Safety requirements The product must meet the applicable hazardous location requirements. 2. Performance requirements If the product is designed to monitor combustible gas and/or oxygen, then it must meet certain performance criteria in ﬁelds such as response time, accuracy and linearity. 3. Quality management certification The manufacturer must have an approved quality management system. 120 M S A G a s D e t e c t i o n H a n d b o o k ATEX Explosive Atmospheres EXPLOSION SAFETY HIERARCHY (European Standard EN 1127-1) Avoid the hazard • Use non-ﬂammable materials, or • Contain the ﬂammable materials in order to avoid the formation of an explosive atmosphere Control the risk If an explosive atmosphere cannot be avoided, even under abnormal conditions: • Prevent ignition of the explosive atmosphere, or • Control the effects of explosions to avoid damage to people and property CONTROLLING EXPLOSIONS Use a protective system to: PREVENT IGNITION Identify potential ignition sources • Electric arcs • Compression ignition • Contain • Electric sparks • Static Electricity • Isolate • Flames • Electromagnetic radiation • Hot surfaces • Ionizing radiation • Suppress – actively • Suppress – passively • Mechanical impact • Chemical reactions • Friction • Acoustic energy • Relieve (vent) the explosion A B 121 M S A G a s D e t e c t i o n A PROTECTIVE SYSTEMS H a n d b o o k B PROTECT IGNITION SOURCES Explosion suppression systems Explosionproof equipment Flame arresters Explosion venting devices Inerting Limitation of concentration of combustibles Dust explosion venting systems Gas explosion venting systems Explosion suppression devices Active explosion extinguishing barriers Explosion barriers for mines Mechanical explosion barriers Category of protection (EU Directive 94/9/EC – ATEX) Mining equipment – Group I Category M1 Very high level of protection. Equipment can be operated in presence of explosive atmosphere Category M2 High level of protection. Equipment to be de-energized in presence of explosive atmosphere Non-mining equipment – Group II Category 1 Very high level of protection. Used where explosive atmosphere is present continuously or for long periods of time (Zone 0, 20)* Category 2 High level of protection. Used where explosive atmosphere is likely to occur in normal service (Zone 1, 21)* Category 3 Normal level of protection. Used where explosive atmosphere is unlikely to occur and would be infrequent and for short time (Zone 2,22)* * EN 1127-1:1997. Clause 6.3 C 122 D M S A G a s D e t e c t i o n H a n d b o o k ATEX Explosive Atmospheres C Methods Of Protection: Standards Category Electrical equipment for ses, vapors and mists (G) Code Cenelec EN IEC General requirements 50014 79-0 M1 M2 1 2 Oil immersion o 50015 79-6 + Pressurized p 50016 79-2 + Powder ﬁlled q 50017 79-5 + Flameproof enclosure d 50018 79-1 + + Increased safety e 50019 79-7 + + Intrinsic safety ia 50020 79-11 Intrinsic safety ib 50020 79-11 Encapsulated m 50028 79-18 Type of protection ‘n’ n 50021 79-15 Category I G 50284* - Category MI 50303* - + 3 + + + + + + + Electrical equipment for flammable dusts (D) Construction and testing Non-electrical equipment 50281-1-1 + + CEN EN General requirements xxxx Pt 1* Restrictive breathing enclosure xxxx Pt 2* Flameproof enclosure xxxx Pt 3* Inherent safety xxxx Pt 4* Constructional safety xxxx Pt 5* Control of ignition sources xxxx Pt 6* *Standards in preparation + E 123 124 T6 T1 T2 T3 T4 T5 T6 Maximum surface temperature 450°C 300°C 200°C 135°C 100°C 85°C * In presence of explosive atmosphere MI – energized* M2 – de-energized* Equipment Category Zone G Gas vapor mist 21 22 20 Zone D Dust Type of explosive Atmosphere (Group II) 2 non-mining 1 – very high 0 protection 2 – high protection 1 3 – normal protection 2 I mining Equipment Group EU Explosive Atmosphere Symbol CE Marking (EU Directive 94/9/EC) CE II I G D D e t e c t i o n Gas Group I Methane (ﬁredamp) Mining Only IIA Propane Typical gases IIB Ethylene classiﬁed according IIC Hydrogen to ignitability of II No ignitability gas/air mixture classiﬁcation T Class Temperature Class (Group II) Referred to ambient of – 20°C to +40°C unless indicated as above Tamb = -40°C to 50°C Explosion Protection Type of Protection symbol Code see table above CENELEC/IEC Ex d IIB E G a s Conformity with European Standard. IEC marking omits this character E Equipment Marking M S A H a n d b o o k Note for reference only, ATEX now supercedes Cenelec ATEX Explosive Atmospheres M S A G a s D e t e c t i o n H a n d b o o k A Selection of Recognized Testing Laboratories North America CSA Canadian Standards Association ENT Entela, Inc. ETL ETL SEMKO, Intertek Testing Service FMGT FM Global Technologies LLC MET MET Laboratories, Inc. MSHA Mine Safety and Health Administration UL Underwriters Laboratories Inc. Australia TestSafe TestSafe Australia Safety Engineering, Testing and Certiﬁcation Services Brazil CEPEL Centro De Pesquisas De Enrgia Electrica France INERIS Institut National De L'Environnemant Industriel Et Des Germany DMT Deutsche Montan Technologie GmbH TUV TUV Product Services GmbH KEMA KEMA Registered Quality, Inc. Russia GOSSTAND ART Gosstandart of Russia 125 M S A G a s D e t e c t i o n H a n d b o o k Approvals System Installation Permanent gas detection systems can be used in both hazardous and nonhazardous rated locations. In North America, if a monitoring system is located in a hazardous area then it must carry the appropriate approvals for that area, (Class, Division and Group). (See “Hazardous Location Classiﬁcation” earlier in this section for descriptions of hazardous area classiﬁcations.) Most hazardous area monitoring applications require Class 1, Division 1 approval, which means that ignitable atmospheres are likely to be present, and thus protection from ignition sources is required to reduce the possibility of an explosion. The three protection methods approved for electrical equipment in this type of area are explosionproof, intrinsically safe and purged/pressurized. I. Explosionproof The device prevents an explosion in a hazardous location by containing any combustion within the device, and thereby preventing it from spreading into the atmosphere surrounding the enclosure. (Note: wires connected to explosionproof classified devices must be contained in an explosionproof classified conduit.) 126 M S A G a s D e t e c t i o n H a n d b o o k Approvals Instead of having both the sensor and the controller rated explosionproof (XP), explosionproof sensor housings are sometimes used with general purpose (GP) controllers that are located in non-hazardous locations. • Widely used in US • More costly to install and maintain • Requires conduit and seals • Non-intrusive calibration enhances installation • If atmosphere ignites, it remains inside enclosure II. Intrinsically Safe The device prevents explosions in hazardous locations through an electrical design in which the possibility of ignition is eliminated. To achieve this, protective components are often added in series with energy storage devices. The protective components eliminate the risk of ignition from sparks or an increased component surface temperature. In this situation, an intrinsically safe sensor assembly is located in the hazardous area and an intrinsically safe barrier is installed in the nonhazardous area to reduce the chance of an electrical spark reaching the hazardous area. If multiple sensors are required, then multiple barriers are used. 127 M S A G a s D e t e c t i o n H a n d b o o k Approvals • Eliminates explosion proof conduit for electrical safety • Requires electrical barriers to limit energy to sensor • Both heat and electrical energy are kept below ignition thresholds III. Purged/ Pressurized Purged/ pressurized equipment cabinets containing spark-producing devices exclude ﬂammable atmospheres. This is done by using compressed air or an inert gas such as nitrogen to pressurize the cabinet’s interior. The unit is also designed to turn off the spark-producing device and trigger an alarm in the event of a pressurization failure. NFPA-496 contains speciﬁc design requirements for purged/ pressurized equipment. There are three types of purging: • Type X purging – reduces the classiﬁcation within an enclosure from Division 1 to nonhazardous • Type Y purging – reduces the classiﬁcation within an enclosure from Division 1 to Division 2 • Type Z purging – reduces the classiﬁcation within an enclosure from Division 2 to nonhazardous When a purged/pressurized system is used, the unit is located in the hazardous area. Purging/ pressurization works in one of two ways: by either preventing outside atmospheres from entering the enclosed unit, or by removing ﬂammable gases from the enclosure by ﬂushing it with inert gas and maintaining internal pressure on the unit. 128 M S A G a s D e t e c t i o n H a n d b o o k Approvals IV. Flameproof With the ﬂameproof method of protection, the sample is pumped from the hazardous area to the GP sensor, which is located in the non-hazardous area. Flashback arrestors are installed at the hazardous area barrier to reduce the chance of an ignition source entering the hazardous area. For each of the preceding circumstances, the detection system components should have a label similar to those shown below, indicating that they have received the approvals appropriate to the environment in which they are to be installed. NOTE: When installing a gas detection system, always follow National Electric Code (NEC) installation requirements and check the manufacturer’s guidelines for calibration. 129 130 Certified to the standard D e t e c t i o n Temperature classification Gas group G a s Protection concept (flameproof) Explosion-proof approval marking Explosion protected M S A H a n d b o o k Area Classification Gas Groups ! WARNING Substitution of components may impair intrinsic safety. The ultimate user must read and understand the instruction manual before use. Failure to follow instructions can result in serious personal injury or death. D e t e c t i o n LISTING NO.E112025. INTRINSICALLY SAFE IN CLASS I, DIV. 1, GROUPS C AND D, HAZARDOUS LOCATIONS, WHEN INSTALLED IN ACCORDANCES WITH DRAWING DSK3098-13. Conduit seals must be installed within 18 inches of enclosure. Disconnect the equipment from the supply circuit before opening. Keep assembly tightly closed when in operation. Failure to comply with this warning can result in ignition of hazardous atmospheres. ! WARNING CLASSIFIED BY UNDERWRITERS LABORATORIES INC.® AS TO EXPLOSION AND FIRE HAZARD ONLY. ENCLOSURE FOR USE HAZARDOUS LOCATION. CLASS I, DIV. 1, GROUPS B, C AND D. TYPE 4X Enclosure Rating G a s MSA CONDULET ASSEMBLY ULTIMA® North American Underwriters Laboratories, Inc approval marking M S A H a n d b o o k 131 132 Area Classification Gas Groups P/N S/N TAG NO: 218923 D e t e c t i o n Input: From MSA Ultima Transmitter AVERTISSEMENT: LIRE ATTENTIVEMENT LES INSTRUCTIONS AVANT DE METTRE EN MARCHE WARNING: UNDERSTAND MANUAL BEFORE OPERATING GROUPS A, B, C & D North American Hazardous Location Certification G a s CSA C22.2 No. 152 CLASS I Canadian Standards Association (CSA) Approval Marking M S A H a n d b o o k Section 6 Sensor Placement Guide M S A G a s D e t e c t i o n H a n d b o o k Quantity and Placement of Sensors MSA gas detection systems monitor the concentration of speciﬁed gases at the immediate location of the sensor. The installation instructions and other information from MSA provide only basic guidance on the properties of the gas in question as well as the effects of certain environmental conditions on the function of the sensor. While this information may be used to help determine the number of sensors needed and the optimum sensor placement, do not rely on this information alone to determine the appropriate quantity and placement of the sensors for any particular site or area to be monitored. It is recommended that the user consult with appropriate industrial hygiene, environmental, and/or health professionals when determining the quantity and placement of sensors to adequately monitor the speciﬁc area in question. WARNING MSA gas detection systems monitor the gas concentration only at the immediate location of the sensor. The user must perform an appropriate environmental analysis on the specific installation site to determine the preferred quantity of sensors and optimum sensor placement. Improper installation can cause a gas release to be undetected and result in serious personal injury or loss of life. 134 M S A G a s D e t e c t i o n H a n d b o o k Sensor Placement Guide MSA Guide to Gas Sensor Selection and Placement STEP 1: To determine where to place sensors, perform an analysis of the potential gas hazards in your facility STEP 2: Create drawings indicating all potential leak sites, as well as the severity of each site’s hazard potential There are two main categories of hazardous locations: A. Potential gas discharge points. These are places where hazardous gases may be released, such as valve stem seals, gaskets, compression ﬁttings and expansion joints. B. Potential contact areas. These are places where hazardous gases may endanger workers or damage equipment or property. Examples include populated areas, conﬁned spaces, pits, stairwells, crawl spaces, shelters, and residential, business and industrial environments located nearby. STEP 3: Since gases do not always behave in the same way, take air ﬂow conditions, as well as potential gas pockets, into consideration before placing sensors. MSA smoke tubes (P/N 458481) can be useful in measuring the direction and rate of air ﬂow to determine areas where gases may accumulate. 135 M S A G a s D e t e c t i o n H a n d b o o k Sensor Placement Guide In general, when placing sensors the following principles should be considered: • Place sensors in areas where the air currents are likely to produce the highest gas concentration, including areas where gas buildup is likely, such as corners or stopping points of moving devices that release gas. • If you are attempting to take a representative room sample, do not place sensors near entrances or fresh air vents (because sample concentration will be diluted by incoming air) unless there is a need to sample that speciﬁc area of the room. • Place sensors close to the possible gas/leak source. • Place combustible gas sensors between the potential leak and the ignition source. • Place toxic (and oxygen deﬁciency) sensors between the potential leak and the populated area, and in the workers’ breathing zone. • Consider ease of access to the sensor for maintenance requirements, such as periodic calibration. Use a remote sensor for high or inaccessible locations. • Avoid mounting sensors near radio transmitters or other RFI-producing sources (e.g., welding activity and induction heaters), to reduce possible RFI interference. • Avoid locations where airborne particles may coat or contaminate the sensor, such as paint booths. • Install in a position that prevents water or dust accumulation on the sensor head (which may impede the diffusion of gas into the sensor). Preferred position is facing downward; horizontal placement is also acceptable. • Facility air intakes are generally good locations for sensors. • Ensure that the entire area in question is sufﬁciently monitored, including little-used areas such as closets, warehouses and other storage areas. • Factor in the vapor density of the monitored gases, when compared to air. 136 M S A G a s D e t e c t i o n H a n d b o o k Sensor Placement Guide Gases Gas Density Sensor Placement carbon dioxide, heavy hydrocarbons greater than air closer to the ground hydrogen, methane less than air near the ceiling carbon monoxide, nitrogen similar to air according to air current path, at or near breathing level (usually 4 to 6 ft. from ﬂoor) Combustible Gas Sensors • Hydrogen and methane are lighter than air, so place sensors near the ceiling, and in ceiling corners where pockets of air may collect. • For electric motor monitoring, place sensors near the ignition source. • Gasoline is heavier than air, so place sensors near—but not directly on—the ﬂoor. • When monitoring multiple combustible gases, calibrate the instrument for the least sensitive gas. Toxic & Oxygen Gas Sensors • Place carbon monoxide and carbon dioxide sensors for indoor air quality monitoring near air intake ducts. • In general, in occupied areas (e.g., conﬁned spaces), monitor for oxygen and toxic gases in the workers’ breathing zone (4-6 feet). This will vary, depending on whether the density of the gas is heavier, the same as, or lighter than, air or oxygen. Toxic & Combustible Sensors • Place sensors near the potential release source for process monitoring applications (e.g., pipelines, valves). • Gas cylinder storage areas: If they are ventilated, place sensor near the return air vent. • Acid/ solvent drum storage areas: These gases are heavier than air (e.g., heavy hydrocarbons) so place sensors close to the ground and in corners where air may collect in pockets. • If the hazard is outside, place sensors near the air intake for both combustible and toxic gas monitoring; if the hazard is inside, place sensors near the exhaust. 137 M S A G a s D e t e c t i o n H a n d b o o k Sensor Placement Guide • Some gases may collect in pockets in room corners, at both ﬂoor and ceiling levels. Place sensors in these areas if necessary. Referigerant Monitor Placement • ASHRAE 15 states that a refrigerant monitor capable of detecting the TLV for a refrigerant gas must be installed in a mechanical equipment room. • Place the end of the sample line in the location most likely to develop a refrigerant gas leak or spill. Such areas include valves, ﬁttings and the chiller itself. Also, monitor any refrigerant storage location. It is good practice to keep all sampling lines as short as possible when an aspirated or pumped sampling system is used. • Since most refrigerant gases are heavier than air, monitor these gases close to the ﬂoor. Any pits, stairwells or trenches are likely to ﬁll with refrigerant gas before the main area. It may be necessary to monitor these locations for refrigerant gas. • If ventilation exists in the chiller room, MSA smoke tubes (P/N 458481) will help to determine the most appropriate gas monitoring locations. • Monitor displays can be placed just outside the doorway of the monitored area. Personnel can check the status of the instrument before entering the area. • ASHRAE Standard 147P states the following; 4.8 Refrigerant Monitor. On Large refrigerating systems for which a refrigerant monitor is required per ASHRAE 15, a refrigerant monitor capable of detecting refrigerant concentrations of 1 ppm by volume or less shall be used to provide early warning of leaks. Guideline for Sensor Placement When monitoring multiple combustible gases, calibrate the instrument for the least sensitive gas. Note: This is for informational purposes only and is intended for use as a general guide to important considerations in sensor placement. It is not intended to serve as an exhaustive review of all considerations. Due to the large number of variables present, each site should be considered individually by a trained professional. The services of a Certified Industrial Hygienist (CIH) or Certified Safety Professional (CSP) should be considered if an onsite survey is required. 138 Section 7 Calibration M S A G a s D e t e c t i o n H a n d b o o k Calibration Instrument Calibration Whether an instrument warns and/ or alarms at the proper time depends on its ability to translate the quantity of gas it detects into an accurate reading. “Calibration” refers to an instrument’s measurement accuracy relative to a known concentration of gas. Gas detectors perform relative measurements: rather than independently assessing the quantity of gas present, they measure the concentration of the air sample and then compare it to the known concentration of the gas that the instrument is conﬁgured to sample. This “known concentration” serves as the instrument’s measurement scale, or reference point. If the instrument’s reference point has moved, then its reading will also move. This is called “calibration drift” and it happens to most instruments over time. (Common causes of calibration drift include the normal degradation of sensors, exposure of the sensor to poisons, and harsh operating conditions.) When an instrument experiences calibration drift it can still measure the quantity of gas present, but it cannot convert it into an accurate numerical reading. Regular calibration with a certiﬁed standard gas concentration updates the instrument’s reference point, re-enabling it to produce accurate readings. There are two methods of verifying instrument calibration: through a functional or “bump” test (or span check) or by performing a full calibration. Each is appropriate under certain conditions. Bump (or Span) Check A bump check is a means of verifying calibration by exposing the instrument to a known concentration of test gas. The instrument reading is then compared to the actual quantity of gas present (as indicated on the cylinder). If the instrument’s response is within an acceptable range of the actual concentration, then its calibration is veriﬁed. When performing a bump test, the test gas concentration should be high enough to trigger the instrument alarm. If the bump test results are not within the acceptable range, then a full calibration must be performed. 140 M S A G a s D e t e c t i o n H a n d b o o k Calibration Full Calibration A full calibration is the adjustment of the instrument’s reading to coincide with known concentrations (generally a certiﬁed standard) of zero and span gases, to compensate for calibration drift. In most cases, a full calibration is only necessary when an instrument does not pass the bump test (or after it has been serviced). Zero Check A zero check is performed to verify that the instrument reads true zero (also referred to as the “baseline”) in an environment in which no amount of target gas is present. Common situations in which a zero check is performed include: • after exposure of the sensor to a sensor contaminant • after the sensor has been exposed to a very high concentration of the target gas • as the sensor ages, since it may gradually drift • after the unit has operated in varying background conditions (e.g. humidity levels) • after exposure to extreme conditions (e.g. high temperature or humidity) If the instrument fails the zero check, then a zero adjustment should be performed, where the instrument is adjusted to true zero. Frequency of Calibration The frequency of calibration depends on the sensor’s operating time, conditions of use (including chemical exposure) and user experience with the instrument. New sensors should be calibrated more often until the calibration records prove sensor stability. The calibration frequency can then be reduced to the schedule set by the safety ofﬁcer or plant manager. Before calibrating the sensors, it is good practice to apply power to the unit to allow the sensor to adapt to the new environment. Sensors should be powered at least one full hour before any calibration attempt is made. 141 Section 8 Resources M S A G a s D e t e c t i o n H a n d b o o k Resources: Code of Federal Regulations (CFR) Title 29 Part 1910, U.S. Department of Labor (DOL), Occupational Safety and Health Administration (OSHA), Washington, D.C. Available online at: www.osha.gov/comp-links.html and www.access.gpo.gov/nara/cfr/waisidx_01/29cfr1910_01.html NIOSH Pocket Guide to Chemical Hazards, Department of Health and Human Services (DHHS), National Institute of Occupational Safety and Health (NIOSH), 85-114. Available online at: www.cdc.gov/niosh/npg/npg.html Occupational Health Guidelines for Chemical Hazards, DHHS, DOL, Washington, D.C., January 1981, DHHS (NIOSH) No. 81-123. Available online at: www.cdc.gov/niosh/81-123.html Fire Protection Guide to Hazardous Materials, 13th edition, National Fire Protection Association (NFPA) One Battery Park, Quincy, MA 02269 (2002). Available online at: www.nfpa.org 2002 TLVs® and BEIs®, American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, OH 45240. Available online at: www.acgih.org Many governmental agencies and other safety organizations with health and safety expertise maintain web sites on the Internet. GOVERNMENT AGENCIES: Agency for Toxic Substances and Disease Registry (ATSDR) www.atsdr.cdc.gov Bureau of Labor Statistics (BLS) www.bls.gov Center for Disease Control and Prevention (CDC) www.cdc.gov Code of Federal Regulations (CFR) www.access.gpo.gov/nara/cfr/cfr-tablesearch.html Department of Transportation (DOT) Ofﬁce of Hazardous Materials Safety www.hazmat.dot.gov Federal Mine Safety and Health Review Commission www.fmshrc.gov National Institute of Environmental Health Sciences www.niehs.nih.gov National Institute for Occupational Safety and Health (NIOSH) www.cdc.gov/niosh/homepage.html National Institute of Health (NIH) www.nih.gov National Safety Council (NSC) www.nsc.org Nuclear Regulatory Commission (NRC) www.nrc.gov Occupational Safety and Health Administration (OSHA) www.osha.gov Ofﬁce for Mine Safety and Health Research www.cdc.gov/niosh/mining U.S. Department of Health and Human Services (US DHHS) www.os.dhhs.gov U.S. Department of Labor, Mine Safety and Health Administration (MSHA) www.msha.gov U.S. Environmental Protection Agency (EPA), Washington, D.C. www.epa.gov 144 M S A G a s D e t e c t i o n H a n d b o o k Resources: PROFESSIONAL & TRADE ASSOCIATIONS: Air and Waste Management Association www.awma.org American Board of Industrial Hygiene www.abih.org American Conference of Governmental Industrial Hygienists (ACGIH) www.acgih.org American Industrial Hygiene Association (AIHA) www.aiha.org American Society of Heating, Refrigerating and Air Conditioning Engineers www.ashrae.org American Society of Safety Engineers (ASSE) www.asse.org Building Ofﬁcials and Code Administrators (BOCA) International www.bocai.org Center for Chemical Process Safety, American Institute of Chemical Engineers www.aiche.org/ccps/index.htm Chemical Manufacturers Association www.cmahq.com Compressed Gas Association www.cganet.com International Society for Measurement and Control (ISA) www.isa.org National Fire Protection Association (NFPA) www.nfpa.org National Safety Council (NSC) www.nsc.org Water Environment Federation® (WEF) www.wef.org World Health Organization (WHO) www.who.int World Safety Organization www.worldsafety.org APPROVALS & STANDARDS ORGANIZATIONS: American National Standards Institute (ANSI) www.ansi.org Canadian Standards Association (CSA) International www.csa-international.org European Committee for Electrotechnical Standardization (CENELEC) www.cenelec.org National Electrical Manufacturers Association (NEMA) www.nema.org Underwriters Laboratories, Inc. (UL) www.ul.com International Electrotechnical Commission (IEC) www.iec.ch GAS DETECTION INSTRUMENTATION SUPPLIER: Mine Safety Appliances Company (MSA) www.msagasdetection.com 145 MSA Instrument Division P.O. Box 427 Pittsburgh, PA 15230 Phone: 1.800.MSA.INST Fax: 1.724.776.3280 www.msagasdetection.com ID 5555-312-MC / Aug 2007 © MSA 2007 Printed in U.S.A.