Flash Point

Flash point of a substance is the lowest temperature at which it can vaporize to form a combustible mixture in air.  At this temperature, if an ignition source (such as a spark or flame) is present, the substance can ignite, but the fire will not be sustained if the ignition source is removed.  Flash point is an important safety measure, as it indicates how easily a substance can catch fire in various conditions.

There are Two Main Methods for Measuring Flash Point

Closed-cup Flash Point  -  The substance is placed in a closed container, and the vapor is tested for flammability.  This generally gives a lower flash point because vapor is contained, making ignition easier.
Open-cup Flash Point  -  The substance is placed in an open container, allowing vapor to escape, which often results in a higher flash point.