Flash fire

A flash fire is a sudden, intense fire caused by ignition of a mixture of air and a dispersed flammable substance such as a solid (including dust), flammable or combustible liquid (such as an aerosol or fine mist), or a flammable gas. It is characterized by high temperature, short duration, and a rapidly moving flame front.

A flash fire is defined by CGSB 155.20-2000 and NFPA 2113 as:

Flash fires may occur in environments where fuel, typically flammable gas or dust, is mixed with air in concentrations suitable for combustion.

In a flash fire, the flame spreads at subsonic velocity, so the overpressure damage is usually negligible and the bulk of the damage comes from the thermal radiation and secondary fires. When inhaled, the heated air resulting from a flash fire can cause serious damage to the tissue of the lungs, possibly leading to death by asphyxiation. Flash fires can lead to smoke burns.

Flash fire is a particular danger in enclosed spaces, as even a relatively small fire can consume enough oxygen and produce enough smoke to cause death of the persons present, whether by asphyxiation or by smoke inhalation.

Protective clothing made of fire-retardant materials (e.g. Nomex) reduces or prevents thermal injury in the body areas that are covered by the fire-retardant material. Even normal clothing can provide partial protection.

Small flash fires can occur in the operating room during surgery where the presence of ignition sources such as electrical instruments or lasers, an oxygen-rich environment, and flammable vapors (e.g. alcohol-based disinfectants) may set the stage for such an accident. While apparently smaller fires go unreported, surgical flash fires have led to burn injuries and fatalities.

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