Hazardous Location Signals
Introduction
The Environment
A
Hazardous Location Environments are those indoor or outdoor
areas where the potential for an explosion and/or fire may exist
due to the presence of flammable gases, liquids and vapours
(Class I), combustible or electrically conductive dusts (Class II), or
easily ignitable fibers, or flyings (Class III).
Classes
B
C
D
The Canadian Standard Association has defined three classes of
hazardous locations:
Class I Locations – Hazardous Gases
Class I locations are areas in which vapours or flammable gases
are or can be present in the air in sufficient quantities to produce
explosive or ignitable mixtures.
Class II Locations – Hazardous Dusts
Class II locations represent areas that are hazardous due to the
presence of combustible and/or electrically conductive dust in the
atmosphere.
Class III Locations – Hazardous Fibers
Class III locations have easily ignitable fibers or flyings that are
present in sufficient quantities to produce ignitable mixtures in
the atmosphere or a risk of fire due to their accumulation on heat
producing equipment.
Divisions
E
F
G
Each of the three hazardous location classes are broken
down into two divisions. In general terms, Division 1 refers to
environments where flammable gases, dusts or fibers exist under
normal operating conditions or are routinely present because
of normal maintenance and repair procedures. Division 1
classification can also apply to areas where flammable materials
can exist as the result of faulty operation of equipment.
Division 2 applies to locations where the potential for an explosion
or fire is reduced because the flammable material is normally
confined within closed systems or containers. Release of these
materials in Division 2 environments would only occur as the
result of an abnormal condition, such as the accidental rupture of
a storage tank.
Group B:
Areas containing hydrogen and other gases or vapours or
equivalent hazards, such as manufactured gas, ethylene oxide or
propylene oxide.
Group C:
Atmospheres containing acetaldehyde, cyclopropane, diethyl
ether, ethylene, or unsymmetrical dimenthyl hydrazine (UDMH), or
other gases or vapours of equivalent hazard.
Group D:
Atmospheres containing acetone, acrylonitrile, alcohol, ammonia,
benzine, benzol, butane, ethylene dichloride, gasoline, hexane,
isoprene, lacquer solvent vapours, naphtha, natural gas, propane,
propylene, styrene, vinyl acetate, vinyl chloride, xylenes, or other
gases or vapours of equivalent hazard.
Typical Class I Hazardous Areas
• Spray painting and finishing areas (residue factors to be a
consideration)
• Utility gas plants
• Petroleum refining production plants
• Petroleum dispensing locations
• Dry cleaning facilities
• Dip tanks containing combustible or flammable liquids
• Plant facilities extracting solvents
• Inhalation anesthetics areas
• Process facilities manufacturing or using pyroxylin (nitro-cellulose) type
plastics (Class II as well)
Class II Groups*
Group E:
Areas containing metal dusts of aluminum, magnesium or their
commercial alloys, and similar metals.
Group F:
Areas containing dusts of carbon black, charcoal, coal or coke.
Group G:
Areas containing dusts of chemicals or grain such as plastics,
flour or starch.
Typical Class II Hazardous Areas
Class I locations are divided into four groups - A, B, C, and D.
Class II locations are divided into three groups - E, F, and G. These
groups designations identify specific types of gases and dusts.
Each group contains materials which have similar characteristics,
including flame temperature, ignition energy and electrical
conductivity.
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Class III locations are not divided into separate group
designations. Allexplosionproof units should be installed per the
latest issue of the CSA Installation Standard.
Typical Class III Hazardous Areas
Groups
Class I Group*
Group A:
Areas containing acetylene.
Flour mills
Feed mills
Grain elevators and grain handling facilities
Fireworks plants and storage areas
Aluminum manufacturing and storage areas
Magnesium manufacturing and storage areas
Coal preparation and handling facilities
Starch manufacturing and storage areas
Confectionary plants
Pulverizer sugar and cocoa manufacturing, packaging and storage
plants
• Spice grinding and storage plants
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Textile mills
Woodworking plants
Furniture manufacturers
Cotton gins
Cotton seed milling plants
Flax plants
Carpet manufacturers
* Refer to Canadian Standard Association Hazardous Location guide for a complete
listing of hazardous materials.
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