flammable

Flammable is a term used in safety and chemistry to describe substances that can ignite and burn in air under ordinary conditions. It applies to solids, liquids, and gases. In common usage, flammable liquids are those with a low flash point—the lowest temperature at which their vapors can form an ignitable mixture with air. If a liquid’s vapors reach or exceed the flash point in the presence of an ignition source, ignition can occur. Some materials have very low flash points and are considered highly flammable, while others have higher flash points and may be described as combustible in some regulatory frameworks. Inflammable is an older synonym that can cause confusion, so many labels now use flammable to denote easily ignitable substances.

Key flammability characteristics include flash point, autoignition temperature, vapor pressure, and the flammable or explosive range. For gases, flammability refers to the concentration range at which mixtures with air can ignite. For solids, ignition may occur from heat, friction, or sparks.

Safety and handling guidelines emphasize keeping flammable materials away from heat, sparks, open flames, and static sources. Use properly grounded and bonded containers, ensure adequate ventilation, and store in approved flammable-liquid cabinets. Label and segregate by compatibility, and follow local regulations and standards such as OSHA, WHMIS/GHS, and related hazard communication requirements. Personal protection should be chosen according to the material and task.

Common examples include gasoline, ethanol, acetone, and toluene. Non-flammable substances include water and many mineral oils.