Flash Fire
Flash fires may occur in environments where fuel, typically flammable gas or dust, is mixed with air in concentrations suitable for combustion.
INDUSTRIAL FLASH FIRE
A Flash Fire is defined by the Canadian General Standards Board (CGSB 155.20) and NFPA (NFPA 2112) as ‘a rapidly moving flame front, which can be a combustion explosion. Flash fire may occur in environments where fuel and air become mixed in adequate concentrations to combust; flash fire has a heat flux of approximately 84 kW/m2 for relatively short periods of time, typically less than 3 seconds’.
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 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.
The purpose of FR clothing worn by a worker should be to minimise the severity and percentage of body burn when exposed to a flash fire. Third-degree burn injury should be prevented while second-degree burns should be minimised. This will create the best chance for worker survivability.
CAN/CGSB-155.20 AND NFPA 2112
The CGSB and NFPA standards are similar: however the NFPA 2112 standard is more comprehensive in its requirements. In addition, NFPA 2112 is the first clothing standard worldwide to include a requirement that textiles used in FR clothing systems be tested in a simulated flash fire exposure using an instrumented mannequin. This provides a quantitative assessment of the predicted body area burn injury for specified exposure energy using a standard garment made from a specific FR textile.
Workers in the Petroleum, Petrochemical and Chemical industries as well as Manufacturing environments where combustible dust can accumulate, encounter daily risk of an incident by flash fire.
WESTEX ULTRASOFT® FLASH FIRE TESTING OVERVIEW
This Westex UltraSoft® flash fire testing video (8:52) was conducted at the University of Alberta’s PCERF Laboratories. PCERF is a protective clothing and equipment research facility and one of the foremost flash fire laboratories in the world. The testing is performed under the protocols of ASTM F1930 and the guidelines of NFPA 2112. The average predicted total area of body burn for the specimens tested must be equal to or less than 40%. Fabrics of differing blends and weights might comply with the standard but they can do so with very different numbers. You can comply at 39% body burn or at 1% body burn, which is an enormous difference. It’s critically important that when you evaluate flame resistant fabrics for potential use in your program that you do not consider anything that does not pass the standard.
NASCO INDUSTRIES, INC. – UNDERSTANDING FLASH FIRE RAINWEAR ASTM F2733
This video (7:58) presented by NASCO Industries, Inc., explains the difference between rainwear that passes a vertical flame test and rainwear that is compliant to ASTM F2733. For workers in the oil and gas industry, this video is a must see.
For the petroleum, petrochemical and chemical industries, the flash fire hazard has been a growing concern. Recently however, several very serious incidents have made the industry look at ways to protect their workforce. The flash fire hazard can be deadly due to the burn injury sustained during an exposure.
A person's ability to survive is a function of their age, the severity and amount of burn injury. Not having the ability to control a workforce's age means an employer must try to reduce the severity and amount of burn injury. As age, severity and amount of burn injury increases, survivability decreases.