inflammable

Inflammable describes a substance that can ignite and burn easily. Substances with low flash points or that vaporize readily—such as gasoline, ethanol, acetone, and many solvents—fall into this category. Inflammable materials pose fire and explosion hazards when exposed to heat, sparks, or friction, and vapors can travel with air to ignition sources.

The term is historically linked to the root inflammare from Latin, meaning to set on fire. The prefix in- here is not a negation; inflammable is not the opposite of flammable. For clarity in safety communications, many organizations use flammable for easily ignitable materials and nonflammable or nonflammable for materials that do not ignite readily. In practice, inflammable and flammable are widely used as synonyms, though inflammable may cause confusion and is less common in modern signage.

Regulations and hazard classifications often refer to a material's flash point to determine flammability. A typical benchmark is a flash point below 100°F (37.8°C) for a material to be described as flammable; higher flash points imply lower immediate risk, though ignition is still possible under sufficient heat or vapor concentration. Safe handling emphasizes keeping ignition sources away, proper storage, ventilation for vapors, and adherence to local codes and safety data sheets. See also flammable materials and fire safety.