Class II Hazardous Areas, Groups E, F and G Explained

The National Electrical Code, or NEC, classifies hazardous areas into three different categories; Class I, Class II, and Class III.  To use equipment in or around these types of areas, caution has to be taken to not cause an explosion or fire.  In the U.S., the Underwriter’s Laboratory, UL, can certify products that can be used safely in these hazardous areas.  EXAIR received our UL Classification for our HazLoc Cabinet Cooler® Systems.  Under certain guidelines, the HazLoc Cabinet Coolers can be used in Class I areas for gases and vapors, Class II areas for flammable dust, and Class III areas for ignitable fibers and flyings.  In this blog, I will cover the Class II hazardous areas.

First, HazLoc Cabinet Coolers are designed to keep electrical components cool during summer months and higher ambient conditions.  They are powered by an EXAIR Vortex Tube which only uses compressed air to generate cold air.  They do not have any moving parts, refrigerant, or refrigerant compressors to fail.  These simple, but effective, cooling devices can be used in the toughest of environments.  With the Vortex Tube as the “engine”, the reliability of the EXAIR HazLoc Cabinet Cooler is unmatched.  It is an easy choice for cooling electrical panels and reduce premature shutdowns.

For a fire to occur, we only need three things as described by the fire triangle; oxygen, fuel, and an ignition source.  For an explosion, we need two other conditions, dust concentration and confinement.  For a Class II area, the fuel is combustible dusts.  “Combustible dusts are fine particles that present an explosion hazard when suspended in air under certain conditions.”1  By NEC standards, dust is categorized into three different groups.  Group E is for metal dust.  This will include aluminum and magnesium dust.   Group F is for carbonaceous dust like charcoal, coal, and carbon black.  And Group G is for non-conductive dust like flour, grain, and plastic.  These fine particles can float and collect on equipment in the surrounding areas.  This collection of material can ignite and cause a fire from a spark or a heat source.  If they are contained like within a panel, then there is a possibility of an explosion.

The ignition source (the second leg of the fire triangle above) is generally from electrical equipment, heat, and static.  Arcs and sparks from motors, contacts, and switches can ignite Class II materials; as well as, high temperatures from equipment.  NEC and UL segregate this hazardous location into two divisions.  Class II Division 1 is in an area where dust material is handled, manufactured, or used.  Class II Division 2 is where the dust material is stored or handled other than in the process of manufacturing.  In both divisions, it is important to protect your electrical systems from these particles “floating” in the surrounding air.

The EXAIR HazLoc Cabinet Cooler Systems are designed to keep your electrical panels cool within hazardous areas like Class II above.  Because system shutdowns from electrical components overheating are costly and potentially dangerous, you can install a HazLoc Cabinet Cooler System without sacrificing your panel’s integrity.  If you would like to discuss in more detail about the different types of EXAIR HazLoc Cabinet Coolers, an Application Engineer at EXAIR will be happy to help you.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

Note 1: Osha.gov publication

Photo: Inflammable Sign Hazardous Symbol European by Clker-Free-Vector-Images.  Pixabay License

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