Some processes may produce fibers or flyings along with dusts or vapors or both. These may or may not exist in the same location may or may not exist in the same location
Where materials are allowed to accumulate, areas may be classified as Class II or Class III, and in some cases, both. Where sanding takes place, dusts are likely to be produced, but in other areas, such as where saws, shapers, and planers are used, flyings are more likely. Areas where finishes are applied may be classified as Class I areas, depending on the types of finished used.. Where more than one hazard exists, the equipment and wiring methods must be selected so that they are appropriate for all the hazards all the hazards
Where both dusts and fibers or flyings are produced or handled, equipment identified for Class II areas can also be used for Class III areas because the Class II requirements meet the dusttight requirements for Class III, but limits on surface temperatures may be lower for the fibers and flyings than for the dusts..

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