A trio of explosions in 1990 in the dust collector system for sever 400 watt YAG laser hole drilling machines was found to be caused by an accumulation of organic material in the metallic flue dust. The explosion covered 75,000 square feet of the building with a visible layer of dust, however, no injuries occurred from the explosion as the dust collector system was in an isolated location.
Analysis of the dust yielded 30 percent organic material with the remainder being metallic oxides. Use of a low flash point aerosol cleaning compound along with wax combined with inadequate cleaning of the dust collector system combined with fan impeller rubbing of casing apparently gave sparks that ignited the dust and set off the explosion.
Corrective action included changing of cleaning compound along with a new easier serviced dust collection system. The presence of aluminum and cobalt in the dust may also have catalytically contributed to the explosive mixture. The chemistry of typical laser drilled metal holes is examined.