500.5 Classifications of Locations
Class II, Division 2.
A Class II, Division 2 location is a location:
 Where combustible dust may be present in the air in quantities that can produce
explosive or ignitable mixtures
 Where combustible dust accumulations are present but there is not enough dust to
interfere with the operation of electrical equipment, but it could interfere with
operation of equipment if there is mishandling of equipment and the dust becomes
suspended in the air.
 Where combustible dust accumulates near electrical equipment it can interfere
with the safe dissipation of heat from electrical equipment, or there could be an
ignitable failure of electrical equipment.
500.6 Material Groups
Class II Group Classifications
 Group E. Atmospheres containing combustible metal dusts, including aluminum,
magnesium, and their commercial alloys, or other combustible dusts whose
particle size, roughness, and conductivity present hazards in the use of electrical
equipment.
 Group F. Atmospheres containing combustible carbonaceous dusts. Coal, carbon
black, charcoal, and coke dusts are examples of carbonaceous dusts.
 Group G. Atmospheres containing combustible dusts not included in Group E or
F, including flour, grain, wood, plastic, and chemicals.
The explosion characteristics of air mixtures of dust vary with the materials involved. For
Class II locations, Groups E, F, and G, the classification involves the tightness of the joints of
assembly and shaft openings to prevent the entrance of dust in the dust- ignition proof enclosure.
If dust enters and accumulates, the layers of dust on the equipment may cause overheating.
Certain dusts may require additional precautions due to chemical phenomena that can
result in the generation of ignitable gases.