This is one of the very best documents for combustible dusts. Although it is from outside the USA, facilities having combustible dusts should sit up and take notice of this information. There is movement in the USA regarding a Com Dust rule from OSHA, but until then it is up to each employer to ensure a safe workplace; this document goes along way to explaining many of the basic safety systems needed for combustible dust. CLICK HERE to download Ontario Fire Code, Illustrated Commentary SECTION 5.10 COMBUSTIBLE DUST PRODUCING PROCESSES (pdf).