A flammable liquid is a combustible liquid which can be easily ignited in air at ambient temperatures, i.e. it has a flash point at or below nominal threshold temperatures defined by a number of national and international standards organisations.
The Occupational Safety and Health Administration (OSHA) of the United States Department of Labor defines a liquid as flammable if it has a flash point at or below 199.4 °F (93 °C). Prior to bringing regulations in line with the United Nations Globally Harmonized System of Classification and Labeling of Chemicals (GHS) in 2012, OSHA considered flammable liquids to be those with a flash point below 100 °F (37.8 °C). Those with flash points above 100 °F and below 200 °F (93.3 °C) were classified as combustible liquids. Studies show that the actual measure of a liquids flammability, its flash point, is dependent on altitude.
Both OSHA and GHS further divide flammable liquids into 4 categories:
|Category I||Category II||Category III||Category IV|
|Hazard Statement||Extremely flammable liquid and vapour||Highly flammable liquid and vapor||Flammable liquid and vapour||Combustible liquid|