“The flash point of a volatile material is the lowest temperature at which vapours of the material will ignite, when given an ignition source.”
In practical terms knowing the flash point is safety critical for many applications as reduced values mean increased risk of explosion or fire. Reduced flash point can indicate ingress of fuel (engines, generators), dissolution of compressed natural gas (compressors), ingress of pumped process fluids (pumps and other systems) or degradation of the lubricant (especially in thermal/heat transfer fluids and other high temperature applications).
Flash point testing can also help detect petrol in diesel fuel.
Engine sump oil in many emergency generators, lifeboat and fire pump engines suffers from fuel dilution due to intermittent running. Monitoring the flash point ensures that this safety critical kit is safe, healthy and ready to go.