Explanation of Intrinsically Safe Classes and Divisions.
The hazardous location ratings are divided into Class, Division, and Group to indicate the existence of flammable gases or vapors, ignitable dust, fibers, or filings under normal or unlikely conditions of operation.
Class
Class l – Areas in which flammable gases or vapors may be present in sufficient quantities to be explosive or ignitable.
Class ll – Areas made hazardous by the presence of combustible dust.
Class lll – Areas in which there are easily ignitable fibers or flyings present, due to the type of material being handled, stored or processed-but in which such fibers or flyings are not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures.
Divisions
Division 1 – Normal Situation: A hazard is present in the everyday normal production operation or during frequent repair and/or maintenance activity.
Division 2 – Abnormal Situation: Potentially hazardous material is expected to be safely confined within closed containers or closed systems, and will be present in the atmosphere only through accidental rupture, breakage, or abnormal operation.
Groups
Group A, B, C & D Gases and vapors in Class l locations are classified into four groups, by the code A, B, C, and D. These materials are grouped according to the ignition temperature of the substance, its explosion pressure and other flammability characteristics.
Groups E, F & G Combustible dust in Class ll locations are classified according to ignition temperature and the conductivity of the hazardous substance.
- Group A
- Acetylene
- Group B
- Flammable Gas, Flammable Liquid Vapor or Combustible Liquid Vapor, such as Hydrogen
- Group C
- Flammable Gas, FlammableLiquid Vapor or Combustible Liquid Vapor, such as Ethylene
- Group D
- Flammable Gas, Flammable Liquid Vapor or Combustible Liquid Vapor, such as Propane
- Group E
- Atmosphere contains combustible metal dust, including Aluminum, Magnesium and other commercial alloys
- Group F
- Atmosphere contains combustible carbonaceous dust, including Coal, Carbone black, Charcoal, and Coke
- Group G
- Atmosphere contains combustible dust, including Flour, Grain, Wood, Plastic, and Chemical
Always check what your company policy is for Classes, Divisions and Groups.