In addition to classifying Hazardous Locations by Class and Division, each location is also classified by its "Group." A Group refers to the type of flammable material present in the atmosphere. See below for a list of all the groups and their materials.
Group A
- Acetylene
Group B
- Acrolein (inhibited)
- Arsine
- Butadiene
- Ethylene oxide
- Hydrogen
- Manufactured gases containing more than 30% hydrogen (by volume)
- Propylene oxide
- Propylnitrate
Group C
- Acetaldehyde
- Allyl alcohol
- n-butyraidehyde
- Carbon monoxide
- Crotonaldehyde
- Cyclopropane
- Diethyl ether
- Diethylamine
- Epichlorohydrin
- Ethylene
- Ethylenimine
- Ethyl mercaptan
- Ethyl sulfide
- Hydrogen cyanide
- Hydrogen sulfide
- Morpholine
- 2-nitropropane
- Tetrahydrofuran
- Unsymmetrical dimethyl hydrazine (UDMH 1, 1-dimethyl hydrazine)
Group D
- Acetic acid (glacial)
- Acetone
- Acrylonitrile
- Ammonia
- Benzene
- Butane
- 1-butanol (butyl alcohol)
- 2-butanol (secondary butyl alcohol)
- n-butyl acetate
- Isobutyl acetate
- Di-isobutylene
- Ethane
- Ethanol (ethyl alcohol)
- Ethyl acetate
- Ethyl acrylate (inhibited)
- Ethylene diamine (anhydrous)
- Ethylene dichloride
- Ethylene glycol monomethyl ether
- Gasoline
- Heptanes
- Hexanes
- Isoprene
- Isopropyl ether
- Mesityl oxide
- Methane (natural gas)
- Methanol (methyl alcohol)
- 3-methyl-1 butanol (isoamyl alcohol)
- Methyl ethyl ketone
- Methyl isobutyl ketone
- 2-methyl-1 -propanol (isobutyl alcohol)
- 2-methyl-2-propanol (tertiary butyl alcohol)
- Petroleum naphtha
- Pyridine
- Octanes
- Pentanes
- 1-pentanol (amyl alcohol)
- Propane
- 1-propanol (propyl alcohol)
- 2-propanol (isopropyl alcohol)
- Propylene
- Styrene
- Toluene
- Vinyl acetate
- Vinyl chloride
- Xylenes
Group E
- Atmospheres containing metal dust, including aluminum, magnesium, and their commercial alloys, and other metals of similarly hazardous characteristics.
Group F
- Atmospheres containing carbon black, coal or coke dust.
Group G
- Atmospheres containing flour, starch or grain dust.