What characterizes the fire point of a combustible liquid?

The fire point of a combustible liquid is characterized as the temperature at which a liquid produces enough vapor to sustain combustion when exposed to an ignition source. At this temperature, the vapors released can ignite and continue to burn as long as there is enough liquid present to provide a vapor supply.

This definition distinguishes the fire point from related concepts like the flash point, which is the temperature at which vapors can ignite but may not sustain combustion. Thus, understanding the fire point is critical for fire investigations and safety assessments, as it indicates a heightened risk of fire and the potential for sustained burning.

The other choices involve definitions that do not accurately capture the essence of the fire point. For instance, while the lowest temperature for flame production might hint at aspects of combustion, it doesn't precisely define the fire point. The concept of temperature needed for the flash point refers to a lower threshold than the fire point itself. The idea of temperature at which it burns indefinitely suggests a state rather than the specific temperature measurement that would define the fire point. Each of these aspects serves a related purpose in understanding fire behavior, but only the definition related to sustaining combustion aligns directly with the fire point.