flammableliquid

Flammable liquid is a term used to describe liquids that can ignite easily and form ignitable vapors under normal conditions. Safety standards typically define a flammable liquid by its flash point—the lowest temperature at which its vapor can form an ignitable mixture with air. In many jurisdictions, liquids with a flash point below 100°F (37.8°C) are classified as flammable; liquids with higher flash points are classified as combustible.

Flammable liquids can emit vapors that travel to potential ignition sources and ignite, sometimes at distances from the liquid itself. They often have high volatility and can produce a broad range of flammable vapor concentrations between the lower flammable limit and upper flammable limit. Because vapors may be heavier or lighter than air, the behavior varies by substance.

Common examples include gasoline, acetone, ethanol, methanol, toluene, and diethyl ether. Not all flammable substances are liquids, and not all liquids are flammable; water and many oils are not flammable under typical conditions. The hazard increases with volatility, vapor pressure, and proximity to ignition sources.

Handling and storage require controls: store in approved flammable-liquid cabinets and away from heat sources, ignition sources, and oxidizers. Use grounded and bonded equipment during transfers; keep containers closed when not in use; provide adequate ventilation. Use labeling and follow hazard communication requirements (for example, H226 or H225 under GHS, and the flame pictogram).

Fire and spill response: extinguish fires with foams, dry chemical, or CO2 as appropriate for the liquid; avoid water jets on hydrocarbon fires. In a spill, seal the area, ventilate, and absorb with inert materials. Personal protective equipment such as goggles, gloves, and flame-resistant clothing should be used when handling flammable liquids.

Regulatory notes: Classifications and thresholds vary by jurisdiction. In the U.S., NFPA 30 and OSHA commonly use a 100°F (37.8°C) flash point threshold to distinguish flammable from combustible liquids. GHS labeling uses H226 for flammable liquids and H225 for highly flammable liquids.