Of the three types of Hazardous Locations, Class III has the least stringent requirements. Fibers (and flyings) have a much larger particle size than dust (Class II) or gases (Class I). That makes fibers easier to contain and control. But that doesn’t mean they aren’t dangerous or pose less of a threat than the other two types of hazards. People killed in Class III incidents aren’t any less dead than those killed in Class II or Class I.