The classes defines the general nature of hazardous material in the surrounding atmosphere.
Class | Hazardous Material in Surrounding Atmosphere |
Class I | Hazardous because flammable gases or vapors are present in the air in quantities sufficient to produce explosive or ignitable mixtures. |
Class II | Hazardous because combustible or conductive dusts are present. |
Class III | Hazardous because ignitable fibers or flying's are present, but not likely to be in suspension in sufficient quantities to produce ignitable mixtures. (Group classifications are not applied to this class.) |
The division defines the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere.
Division | Presence of Hazardous Material |
Division 1 | The substance referred to by class is present during normal conditions. |
Division 2 | The substance referred to by class is present only in abnormal conditions, such as a container failure or system breakdown. |
The group defines the hazardous material in the surrounding atmosphere.
Group | Hazardous Material in Surrounding Atmosphere |
Group A | Acetylene |
Group B | Hydrogen, fuel and combustible process gases containing more than 30% hydrogen by volume or gases of equivalent hazard such as butadiene, ethylene, oxide, propylene oxide and acrolein. |
Group C | Ethyl and ethylene or gases of equivalent hazard. |
Group D | Gasoline, acetone, ammonia, benzene, butane, cyclopropane, ethanol, hexane, methanol, methane, natural gas, naphtha, propane or gases of equivalent hazard. |
Group E | Combustible metal dusts, including aluminum, magnesium and their commercial alloys or other combustible dusts whose particle size, abrasiveness and conductivity present similar hazards in connection with electrical equipment. |
Group F | Carbonaceous dusts, coal black, charcoal, coal or coke dusts that have more than 8% total entrapped volatiles or dusts that have been sesitized by other material so they present an explosion hazard. |
Group G |
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