inflammability

Inflammability is the property of a material that describes how easily it can ignite and sustain combustion. It covers gases, liquids, and solids and is assessed by different criteria. In common usage, flammable refers to materials that ignite readily, while combustible describes those that require more heat. The term inflammable has historically been used to mean the same as flammable, from the Latin inflammare meaning to set on fire. Because of potential confusion, many safety resources now prefer flammable and nonflammable; some older signs still use inflammable.

Measuring flammability involves flash point, autoignition temperature, and flammable limits. A liquid’s flash point is the lowest temperature at which its vapors can ignite in air; liquids with flash points below 37.8 C (100 F) are typically deemed flammable, while higher flash points indicate combustible liquids. Gases have a flammable range in air and an autoignition temperature. Solids ignite through heat, friction, or sparks and are generally described as combustible.

Regulatory labeling and handling emphasize avoiding ignition sources and controlling vapors. In workplaces, the terms flammable and nonflammable are common; safety data sheets may use GHS classifications such as H225 Flammable liquid. Practical guidance includes storing flammable substances away from heat, ensuring adequate ventilation, and using grounding and bonding to prevent static discharge during transfer.