Flash Point

Last updated: January 2, 2021

What Does Flash Point Mean?

Flash point refers to the lowest temperature at which a liquid emits enough vapor to ignite when exposed to air. Flash points are measured at the surface of the liquid at the point where the material converts from a liquid to a gaseous state. This area of transition from liquid to gas is referred to as the vapor zone.

U.S. Occupational Safety and Health Administration (OSHA) set forth guidelines for measuring the closed-cup flash point of a liquid using a standard closed container and an open-cup flash point using an open container.

To determine the flash point of a substance, a specified amount of the fluid is exposed to oxygen and a flame. The lowest temperature at which exposure to the flame triggers ignition at the vaporization zone is the flash point.


WorkplaceTesting Explains Flash Point

When categorizing chemicals in the workplace, the flash point of a liquid is used to classify the liquid as flammable or combustible. This categorization is then used to assess the risk of fire or explosion associated with the chemical.

The vapor from a liquid with a low flash point is capable of igniting and burning at room temperature. Thus, such liquids must be stored and handled in a way that prevents a concentration of vapors in the immediate atmosphere that could be ignited and trigger an explosion or fire.

The American Society for Testing Materials (ASTM) categorizes liquids as flammable if it has a flash point of 93 degrees Celsius (199.4 degrees Fahrenheit). Other systems of categorization, such as the Canadian Centre for Occupational Health and Safety (CCOSH), distinguish between flammable liquids having a flash point of 37.8 degrees Celsius (100 degrees Fahrenheit) or lower and combustible liquids, or those having a flash point above 37.8 degrees Celsius.


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