Class III areas and Article 503 do not consider or cover fibers or flyings that are in suspension in air. Fibers and flyings are large enough that they will settle out of the air rapidly, so the primary concern is that they may accumulate and form easily ignitable quantities. These materials will burn readily and rapidly readily and rapidly
In some cases, a flash fire may spread so rapidly through accumulated fibers that the materials burn completely without igniting any structural parts. Nevertheless, the shortage of oxygen that may result, along with the resulting smoke and other toxic products of combustion, represent a serious hazard to the building occupants, if not to the building itself.when they are ignited. They may be ignited either by stray arcs or sparks from electrical equipment or by high surface temperatures on electrical equipment.

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