What is Considered a Hazardous Location?
The Occupational Safety and Health Administration (OSHA) defines a hazardous location as environments that host combustible gases, liquids, vapors, dust or fibers/flyings. According to OSHA Publication 3073, in order for a hazardous location classification to be valid, concentration levels of combustible materials inside the area must be sufficient enough to generate explosions, fires and ignitions. The US-based safety organization calls for explosion proof methods to maintain safety in hazardous locations. Moreover, specific installation methods must be applied to prevent interactions with flammable compounds.
NEC and CEC Hazardous Locations
In the National Electric Code (NEC), as well as the Canadian Electric Code (CEC), considerations for hazardous locations are extended to include areas where combustible substances are always present during normal, everyday operations (Division 1) or sites that contain flammable compounds only during abnormal working conditions, such as emergencies and equipment failure (Division 2).
When it comes to protective measures for equipment used in hazardous locations, “explosion proof” may refer to protection for Division 1 rated sites, while “hazardous location” may refer to protection for Division 2 rated facilities.
Devices used in hazardous locations are classified as: Class I, Class II or Class III. A Class I rated site deals with explosive gases, liquids and vapors; while a Class II rated area hosts flammable or metallic dust. A Class III rated environment is a location where combustible fibers/flyings are present.
Hazardous Location Groups
Groups can be applied to hazardous location ratings to specify certain flammable compounds that are addressed by explosion proof devices:
• Group A: Acetylene
• Group B: Hydrogen, Ethylene Oxide, Propylene Oxide
• Group C: Ethylene, Ethyl Ether
• Group D: Butane, Gasoline, Acetone, Propane
• Group E: Magnesium, Explosive Alloys
• Group F: Coal, Carbon Black, Charcoal
• Group G: Flour, Wood, Grain, Chemicals
To prevent ignitions due to high temperatures, equipment used in hazardous locations can come with temperature ratings. Lastly, to greatly reduce or eliminate the creation sparks, non-sparking or spark-resistant materials are utilized to manufacture explosion proof systems. Examples of such robust materials include: copper-free aluminum, polycarbonate, thermoplastics, glass, polyamide, etc.