How do we determine our explosion risk?

Once you have identified combustible dust in your facility, OSHA says that you should carefully assess the following to determine the potential for fire and explosions:

• Processes which use, consume, or produce combustible dusts;
• Open areas where combustible dusts may build up;
• Hidden areas where combustible dusts may accumulate;
• Means by which dust may be dispersed in the air; and
• Potential ignition sources.

The amount of dust accumulation necessary to cause an explosive concentration can vary greatly. This is because there are so many variables – the particle size of the dust, the method of dispersion, ventilation system modes, air currents, physical barriers, and the volume of the area in which the dust cloud exists or may exist. As a result, simple rules of thumb regarding accumulation (such as writing in the dust or visibility in a dust cloud) can be subjective and misleading. The hazard analysis should be tailored to the specific circumstances in each facility and the full range of variables affecting the hazard.

Many locations need to be considered in an assessment. One obvious place for a dust explosion to initiate is where dust is concentrated. In equipment such as dust collectors, a combustible mixture could be present whenever the equipment is operating. Other locations to consider are those where dust can settle, both in occupied areas and in hidden concealed spaces. A thorough analysis will consider all possible scenarios in which dust can be disbursed, both in the normal process and potential failure modes.

After hazards have been assessed and hazardous locations are identified, employers can then implement prevention and control methods to reduce the risk of fires and explosions caused by combustible dust.