Classifications for flammable & combustible liquids
Flammable and combustible liquids are part of our everyday life and the use and storage of them at home and work is regulated for our safety.
The National Fire Protection Association establishes the classifications for flammable and combustible liquids and the Department of Labor's Occupational Safety and Health Administration sets the rules and regulations in working environments for those liquids.
The National Fire Protection Association's classifications were established together with the Department of Transportation and OSHA to make a standardised list of liquids in order to set safety policy. The classifications are used to establish work safety requirements and transport restrictions and regulations. Classes are determined by the temperature at which the liquid vaporises in the air and can ignite in the air. This temperature is called the flash point.
The flash point of flammable liquids is below 37.8 degrees Celsius. Class IA liquid's flash point is below 22.8 degrees C and the boiling point is below 37.8 degrees C. Class IA liquids include diethyl ether, ethylene oxide, acetaldehyde and pentane. Class IB flammable liquids have a flash point below 22.8 degrees C and a boiling point at or above 37.8 degrees C. Class IB liquids include acetone, benzene, cyclohexane, ethanol, methyl alcohol, butyl alcohol and toluene. Class IC liquids have a flash point above 22.8 degrees C and a boiling point less than 37.8 degrees C. Class IC liquids include xylene, turpentine and isopropanol.
Combustible liquids have a flash point above 37.8 degrees Celsius. Class II combustible liquids have a flash point between 37.8 and 60 degrees Celsius and include diesel fuel, motor oil, kerosene and cleaning solvents. Class IIIA combustible liquids have a flash point between 141 and 199 degrees and include home heating oil, acetic acid, oil-based paints, linseed oil and mineral oil. Class IIIB combustible liquids have a flash point of 200 degrees and above and include cooking oils, lubricating oils, and motor oil.
Flammable and combustible liquids are volatile and ignite easily. Vapours in the air will burn until the ignition source is removed and fires with flammable and combustible liquids can burn intensely and for long periods of time. Storage regulations for flammable and combustible liquids are extremely detailed and strict. In biological and chemical labs, chemical plants, schools, hospitals and other working environments, the amount of flammable and combustible liquid stored in one area is restricted and the containers and cabinets required to store them are regulated using the liquid's classification.