What is a flash point? It is the temperature at and above which a liquid gives off enough flammable vapor to form a mixture with air that can be ignited by contact with a hot surface, spark, or flame. Checking the flash point of your compressor, pump, turbine and/or seal oil in a hydrocarbon environment is a valuable way to reduce safety risk. An oil's typical flash point is 400°F. If the equipment has a process leak and mixing with the oil, the oil's flash point can be greatly reduced, thus creating a fire/explosion hazard. Simply put, the lower the flash point, the greater the risk!


Checking the flash point of engine oils is a good way to check for excessive fuel dilution. No. 2 diesel fuel has a flash point of around 180°F, while gasoline has a flash point below 0°F. Most engine oils have a flash point around 425°F. A 2% diesel fuel dilution will lower the flash point of engine oil to about 400 degrees, while a 2% gasoline fuel dilution will even be lower.

Approximately two ounces of oil are poured into an open brass cup. The flash cup is then placed on top of a heater which slowly raises the temperature of the oil. A calibrated thermometer is placed in the oil to monitor the temperature, and a small flame is placed approximately 1/2" above the cup. When the oil gets hot enough to give off flammable gases, the flame will flash the gases. The temperature of the oil at this point is the flash point. The temperature at which the lube oil is capable of sustaining a flame is the fire point.

FLASH AND FIRE POINT