Which is an example of a combustible liquid?

• A. Water
• B. Mineral oil
• C. Gasoline
• D. Vegetable oil

Answer: (B)

Combustible liquids are those that won’t ignite at room temperature but can burn once heated to their flash point—the temperature at which enough vapor is released to form an ignitable mixture with air. Gasoline has a very low flash point, so it’s classified as flammable. Water can’t burn because it doesn’t produce flammable vapors, and it doesn’t ignite. Mineral oil, on the other hand, has a much higher flash point, so it won’t ignite until it’s heated to a higher temperature. That makes it a combustible liquid. (Vegetable oils also have relatively high flash points and are generally considered combustible, but mineral oil is a clear, reliable example of a combustible liquid.)