A combustible dust rule being developed by OSHA should include provisions that specifically address metal dust and should be published within one year, says the U.S. Chemical Safety Board (CSB).

The recommendation is part of a final report on three fires at a powdered metal plant that killed five workers and injured three.

CSB's investigation found that significant amounts of fine iron powder had accumulated over time at the facility, and that the company knew from its own testing and experience with flash fires in the plant that the dust was combustible. Yet the company failed to take steps to reduce the hazards through basic housekeeping and engineering controls, such as enclosing conveyors and installing properly designed dust collection equipment.

Investigators also found that the company did not institute procedures such as combustible gas monitoring or provide training for employees on avoiding flammable gas fires and explosions.

The three accidents were entirely preventable, according to CSB. In January 2011, a flash fire sparked by a bucket elevator and fueled by combustible iron dust killed two workers. Two months later, a furnace fire: also fueled by combustible dust: injured one worker. A third explosion, caused by a hydrogen leak and further fueled by combustible metal dust, killed three more workers.

CSB has also released a safety video, "Iron in the Fire", that features computer animations depicting each accident.