Which liquids are those with a flashpoint at or above 100 °F (37.8 °C)?

• A. Combustible liquids
• B. Flammable liquids
• C. Nonflammable liquids
• D. Hazardous liquids

Answer: (A)

Flashpoint is the lowest temperature at which a liquid’s vapors can ignite in air. Liquids with flashpoints below 100 °F are considered flammable because they can form ignitable vapor mixtures at relatively low temperatures. Those with flashpoints at or above 100 °F are classified as combustible, meaning ignition risk appears only at higher temperatures. Therefore, liquids with a flashpoint at or above 100 °F are combustible liquids. For example, heating oil with a flashpoint around 140 °F is combustible, while gasoline, with a much lower flashpoint, is flammable. Nonflammable and hazardous liquids aren’t defined by this 100 °F cutoff in the same way.