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NOTE: This is an unformatted excerpt from our online fire protection training library.

Classification Basics

From NEC 500.1 (emphasis added):

"Articles 500 through 504 cover the requirements for electrical and electronic equipment and wiring for all voltages in Class I, Divisions 1 and 2; Class II, Divisions 1 and 2; and Class III, Divisions 1 and 2 locations where fire or explosion hazards may exist due to flammable gases, flammable liquid-produced vapors, combustible liquid-produced vapors, combustible dusts, or ignitible fibers/flyings."

From NEC 500.6(A)(2):

        "(2)  Group B. Flammable gas, flammable liquid-produced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode, having either a maximum experimental safe gap (MESG) value less than or equal to 0.45 mm or a minimum igniting current ratio (MIC ratio) less than or equal to 0.40. [NFPA 497:3.3.5.1.2"
NOTE: This is an unformatted excerpt from our online fire protection training library.

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