A flash fire spreads rapidly through a diffuse fuel, such as dust, gas, or the vapors of an ignitable liquid, without the production of damaging pressure. The intensity of a flash fire depends on the size of the gas or vapor cloud. Hydrocarbon (oil and gas) flash fires generate temperatures of 1,000 to 1,900 degrees Fahrenheit. The duration of a flash fire can last up to five seconds.
This information is quoted in “NFPA 2112: Standard on Flame Resistant Garments for Protection of Industrial Personnel Against Flash Fire.” This voluntary standard of the National Fire Protection Association (NFPA) specifies the minimum performance requirements and test methods for flame-resistant (FR) fabrics and components and the design and certification requirements for garments for use in areas at risk from flash fires.