According to NFPA 1, a highly volatile liquid is defined as which of the following?

• A. A liquid with a boiling point of 68 degrees F or higher
• B. A liquid with a boiling point well above room temperature
• C. A liquid with a boiling point of less than 68 degrees F
• D. A liquid with a flash point below 0 F

Answer: (C)

In NFPA 1, how volatile a liquid is classified hinges on its boiling point. A liquid is considered highly volatile if its boiling point is below 68°F, because at typical room temperatures it readily forms vapors that can mix with air to create flammable or explosive conditions. The threshold is set at 68°F to reflect that liquids boiling under this temperature will vaporize easily in normal environments, making them more hazardous. The flash point, while important for flammability, isn’t the criterion used here. So the best description is a liquid with a boiling point under 68°F.