One of the most frequently neglected safety and environmental concerns is the accumulation of fine dust particles at the work place. Fine dust particles can become combustible and pose a safety and fire hazard. The National Fire Protection Association defines combustible dust as particles that are smaller than 420 microns in diameter. These are the same particles that pass through a #40 U.S. standard sieve.
However – the combustible factor also depends on various other factors such as shape, moisture and content of the particle. So you may have particles that are larger than 420 microns and still pose a fire hazard.
Combustible particles exist in many industries; food manufacturing (candy, sugar, starch, flour and feed), furniture, woodworking, metal grinding, textile, dyes, coal, etc. Most synthetic organic material can form combustible dusts.
Normally noncombustible material can be transformed into combustible dust if it undergoes a manufacturing process that turns it into finely divided state. Very often, a primary explosion near a collection of fine particles will trigger a massive secondary explosion.
Here is a short video from the Chemical Safety Board on a combustible dust explosion at Imperial Sugar that killed 14 persons. It describes the events and causes that lead to the deadly explosion:
Note that the plant management was aware of the existing danger of combustible dust explosion as evidenced by earlier internal inspection, according to the CSB. But the dust was allowed to continue ot accumulate. This is another classic example of why you should pay attention to your own internal audit findings and act on them in a timely manner.
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