The Occupational Safety and Health Administration (OSHA) has issued more realistic guidance to field inspectors looking at accumulations of wood dust. The new guidance provides explicit instruction on how to address dusts, such as wood, with bulk densities of less than 75 lb/ft3.
OSHA also acknowledges in the guidance that "very low bulk density materials…may not create a deflagration hazard even at an accumulation level of ¼ inch…" or more, depending on the bulk density and other attributes of the dust.
AWC is pleased that OSHA has decided to consider the true bulk density of a dust in order to assess safe limits for accumulation. For comparison, OSHA's web-based reference provides a bulk density for wood shavings as 8 lb/ft3, with a maximum of 16 lb/ft3, or approximately one-ninth of what they had been using for wood.
Going forward, instead of relying on a 1/32 inch maximum accumulation criterion, OSHA inspectors are now being asked to calculate a maximum safe accumulation layer, specifically taking into account bulk density for the particular material. In situations involving very low bulk density dusts, inspectors can now also send dust samples collected to a laboratory for a density determination where the material is very light; the layer thickness is greater than ¼ inch and not more than one inch; and, the accumulation extends over 5 percent of the floor area of a room or a building or 1000 ft2, whichever is less.