How should a combustible dust be rated?
HMIS® has adopted the OSHA criteria for determining flammability and physical hazards. Information on determining material ratings is located in Chapter 7 of this manual. Care should be used in the application of flammability and physical hazard ratings to combustible dusts. The explosion hazard potential of a combustible dust is similar to the explosion hazard of flammable liquid vapors or combustible gases. The major difference is that a combustible dust must be put into suspension by some outside mechanism before an explosion can occur, whereas the flammable liquid vapors and combustible gases have their own capability of diffusing with air to provide possible explosive mixtures. Keep in mind that the HMIS® is intended to provide ratings for normal workplace use, rather than worst-case conditions. Therefore, the HMIS® user should not misapply unnecessarily high flammability ratings to combustible dusts so as to reflect the worst-case scenario. Doing so will confuse the end user and
