Flammability is based off of how well a substance reacts with an oxidant, which is most commonly oxygen, and gives off a flame. Almost every element can form compounds with oxygen, but their flammability differ. For example, sodium burns violently in oxygen, while silver can't react with air even when heated. Some substances can also burn in oxidants other than oxygen. For example, magnesium can burn in nitrogen gas.
Notable examples[]
- Materials such as carbon tetrachloride, silicon dioxide, perfluorohexane, water do not burn under typical fire conditions. Examples of intrinsically noncombustible materials are concrete, stone, and sand.
- Some substances require considerable preheating, under all ambient temperature conditions, before ignition and combustion can occur (e.g., mineral oil, ammonia, ethylene glycol).
- Some chemicals must be moderately heated or exposed to fairly high ambient temperature before ignition can occur (e.g., diesel fuel, paper, sulfur and multiple finely divided suspended solids that do not require heating before ignition can occur).
- Materials (including finely divided suspended solids) that can be ignited under almost all ambient temperature conditions (e.g., acetone, ethanol)
- Certain chemicals rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily (e.g., gasoline, acetylene, propane, hydrogen gas, diborane, tert-Butyllithium).