Effect of Particle Shape and Size Distribution on Combustible Dust Explosibility

NFPA 664 standard on wood and cellulosic materials proclaims that dry wood dust can not present a flash fire or explosion hazard if 50% of the particles (by mass) is greater than 420 microns. Similarly, NFPA 61 standard on agricultural and food materials proclaims only the material that all pass through 420 micron sieve can present a flash fire or explosion hazard. These definitions are clearly an outcome of the consensus process which is often unencumbered by science or test data.

This paper will focus on the effect of particle size distribution on dust explosibility. New data will be presented.