North American Hazardous Location Class and Division System
The Class and Division system is the North American method for classifying hazardous locations where flammable gases, dusts or fibres may be present. Class defines the type of hazardous material, Division defines how likely the hazard is to occur, and equipment such as that certified by UL or FM Approvals must match the classification of the area.
Key Takeaways
The Class and Division system classifies hazardous locations in the United States and Canada.
Class I covers gases and vapours, Class II covers combustible dust and Class III covers fibres and flyings.
Division 1 indicates a hazard present in normal operation and Division 2 a hazard present only abnormally.
Equipment is certified by bodies such as UL and FM Approvals for a specific class and division.
The Class identifies the nature of the hazardous material. Class I covers flammable gases and vapours, Class II covers combustible dusts and Class III covers easily ignitable fibres and flyings.
The Division describes how likely the hazardous material is to be present. Division 1 covers locations where the hazard exists under normal operating conditions, while Division 2 covers locations where it is present only under abnormal conditions.
Equipment for these areas is assessed by certification bodies such as Underwriters Laboratories and FM Approvals. Rugged devices intended for North American hazardous sites state the class and division for which they are approved.
Frequently Asked Questions
A location where flammable gases or vapours are present in sufficient quantity under normal operating conditions.
Both classify hazardous areas, but Class and Division is the North American system while zones are used under ATEX and IECEx. They are broadly equivalent in purpose.
Bodies such as Underwriters Laboratories and FM Approvals assess and certify equipment for specific class and division ratings.
Division 1 areas have the hazard present in normal operation, while Division 2 areas have it present only under abnormal conditions.
From Theory to Application
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