What is a flashpoint?

A flashpoint is the lowest temperature at which the vapors of a volatile material can ignite. This is an important factor when evaluating safety precautions in any area where flammable materials are used. In many factories great care must be taken to ensure the temperature never approaches the flashpoint of various materials or it could cause serious dangers.


Measuring Flashpoint

When working to determine the flashpoint of a material there are two measurements that can be used:

  • Open Cup – The open cup method is where a sample is contained in an open cup and it is slowly heated. At various intervals a flame will be brought over the surface. When the solution is heated sufficiently to produce vapors that can ignite, that will be the open cup flashpoint.
  • Closed Cup – There are actually two types of closed cup measurements. The first is where the vapors above a liquid and the vapors are of not of equal temperature and the other is where they are. In either case, the cups are sealed with a lid that has a way for a flame to be introduced. As with the open cup measurement, the temperature at which there is ignition is the flashpoint.

Flashpoint of Common Items

Knowing the flashpoint of various items can help when planning out workplace safety. The following are some of the more common types of fuel or other materials where the flashpoint is important. All degrees are listed in Fahrenheit:

  • Ethanol (70%) – 61.9 Degrees
  • Diesel Fuel – 126 Degrees
  • Jet Fuel – 100 Degrees
  • Vegetable Oil – 621 Degrees
  • Biodiesel – 266 Degrees

Flashpoint vs Autoignition Temperature

A common misconception about flashpoints is that it is the temperature at which the material will ignite. That is actually known as the autoignition temperature. If one were to take vegetable oil and put it in an area that was 621 degrees (its flashpoint) it would not actually ignite unless there were an ignition point (a flame or spark, for example). Despite this fact, however, one must always take great care whenever working with hazardous materials in temperatures anywhere near their flashpoint or autoignition temperature.

Additional Flashpoint facts:


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