Dust

The NFPA defines a combustible dust as ‘any finely divided solid material that is 420 micrometers or smaller in diameter and that presents a fire or explosion hazard when dispersed and ignited in air.’

References:

– NFPA 654, 2013, ‘Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible’. http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=654 [Retrieved 11/05/2015]

– NFPA 68, 2013, ‘Standard on Explosion Protection by Deflagration Venting’.

– Crowl, D. A. and J. F. Louvar (2001). Chemical process safety: fundamentals with applications, Pearson Education.