Flammable And Combustible Liquids Definitions:

As defined through DOT, OSHA, and the Flammable and Combustible Liquids Code and National Fire Protection Association Standard, NFPA 30, a flammable liquid is one having a flash point below 100ºF, that having a vapor pressure not exceeding 40 psia at 100ºF.  The combustible liquids are those along with flash points at or above 100ºF, but below 200ºF.  While combustible liquids do not ignite as simply as flammable liquids that must be handled along with caution since of their ability to ignite under certain conditions. Combustible and Flammable liquids are additional subdivided through NFPA 30 within classes as follows.

Class I  - These liquids having flash points below 100ºF.

IA - Those liquids having flash points below 73ºF and having a boiling point below 100ºF.

IB - Those liquids having flash points below 73ºF and having a boiling point at or above 100ºF.

IC - These liquids having flash points at or above 73ºF and below 100ºF.

Class II  - These liquids having flash points at or above 100ºF and below 140ºF.

Class III - These liquids having flash points above 140ºF.

IIIA - Those liquids having flash points at or above 140ºF and below 200ºF.

IIIB - Those liquids having flash points above 200ºF.

Flammable and combustible liquids vaporize to form flammable combination while they are stored in open containers, while they leak or are spilled, or while heated.  The hazard which exists from these mixtures is hugely dependent upon the flash point of the liquid, a concentration of the combination, and the potential of a source of ignition at a temperature enough to cause the combination to burst into flame.

Because it is the vapor-air mixture established from the evaporation of the liquid that poses the hazard, exposures of huge liquid surface areas and sources of heat should be prevented or avoided during storage or handling of these liquids.