Which property is most directly linked to the potential for vapor release in a pool fire scenario?

• A. Density
• B. Vapor pressure
• C. Boiling point
• D. Heat of combustion

Answer: (B)

Vapor release in a pool fire is governed by how readily the liquid forms vapor at the ambient temperature and heat input, which is captured by its vapor pressure. The higher the vapor pressure at the operating temperature, the more fuel vapor sits above the liquid, creating a larger, potentially flammable vapor-air mixture that can feed and sustain the fire. Density matters for how vapor moves—whether it tends to rise or stay near the surface—but it doesn’t tell you how much vapor will be generated. Boiling point relates to the temperature at which the liquid boils, but vapor generation occurs well before reaching that point if the vapor pressure is sufficient. Heat of combustion describes how much energy is released when the vapor actually burns, not how much vapor is produced in the first place.