A fire that spreads by means of a flame front rapidly through a diffuse fuel, such as dust, gas, or the vapors of an ignitable liquid, without the production of damaging pressure
Flash fires generate temperatures in the range from 1000ºF to 1900ºF.
The main hazard of the rapidly moving flame front is ignition of flammable materials including clothing.
Similar to an arc flash, FR clothing is a precaution designed to give personnel some time to escape the situation.
The major test in the certification program is the full-scale flash fire test (Instrumented Mannequin) according to ASTM F1930 Standard Test Method for Evaluation of Flame Resistant Clothing for Protection Against Fire Simulations Using an Instrumented Mannequin.
An instrumented mannequin is a unique and very complex test system representing a human body. It is equipped with a minimum of 100 thermal energy sensors uniformly distributed within each area in the mannequin. After the test garment is on, the mannequin is exposed to flames simulating a flash fire. The duration of flame exposure is three seconds. Data from the test is used to calculate burn percentage for second and third degree burns and distribution on the body.