Flammability

Overview
Flammability is the ease with which a substance will ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is subject to quantification through fire testing. Internationally, a variety of test protocols exist to quantify flammability. The ratings achieved are used in building codes, insurance requirements, fire codes and other regulations governing the use of building materials as well as the storage and handling of highly flammable substances inside and outside of structures and in surface and air transportation. For instance, changing an occupancy by altering the flammability of the contents requires the owner of a building to apply for a building permit to make sure that the overall fire protection design basis of the facility can take the change into account.

Vapour pressure

 * The vapour pressure is an important parameter in determining the ease of ignition. The higher the vapour pressure, the more flammable vapour is evolved from a free liquid surface at a given temperature.

Examples of flammable liquids
Flammable liquids include, but are not limited to:
 * gasoline
 * ethanol
 * acetone
 * Diesel

Examples of nonflammable liquids

 * Water
 * Sodium silicate

Linguistics: Flammable vs. inflammable
The word "inflammable" came from Latin inflammāre = "to set fire to", where the prefix in- means "in" as in "inside" (compare English "in flames"). But there have been instances of people thinking that this "in-" prefix means "not" as in "invisible" and "incombustible" etc, and thus wrongly thinking that "inflammable" means "cannot burn". To avoid this safety hazard, the shortened word "flammable" has come into use in recent years.