Some information on the flash point and fire point of cooking oil.
How do Grease Fires Start?
Now, to the part you probably didn't know. There is more than one way for a kitchen grease fire to erupt. First, let's say you are heating oil in a pan on the stove. It has to get to a certain high temperature before it can ignite, or, in other words, catch on fire. Why?
Well, that is because liquid oil itself does not burn. Rather, it is the vapor from oil that has reached its boiling and vapor point that ignites. There are three things, for our purposes, to understand. The flash point, the fire point, and the ignition point.
Flash Point of Cooking Oils
The flash point of a flammable liquid material is the lowest temperature at which the material, our vegetable oil, can form an ignitable mixture in air. This means that it is giving off vapors that can be ignited by an ignition source. Usually, at home, this ignition source is the source of heat that is heating the oil, your gas burner or electric stove. As already mentioned, an electric burner is more likely to ignite a hot cooking oil than a gas flame.
The ignition source has to be somewhat hotter than the oil. Now, comes the fire point. The fire point is the temperature that must be reached for the vapor to continue to burn after being ignited, even if the ignition source is removed. This explains why, as I mentioned above, sometimes just turning off the flame will stop the fire. At a certain temperature, the oil will need a continued source of heat to continue burning. When you turn off an electric stove, of course, the burner remains hot for a while, so you are not really immediately removing the heat source. On a gas stove, once the flame is off, it is possible for an oil that has reached flame point, but not fire point, to go out. But don't depend on it! For the fire to be self-sustaining, the temperature has to be a little hotter than the initial flash point.
The fact that vegetable and animal cooking oils have very high flash points is part of why they are not considered hazardous materials. Consider a household chemical which will ignite at room temperature and compare this with cooking oil, which must be heated to a very high temperature before a flame or spark can set it off. The flashpoint, in fact, is used as a dividing line between when a liquid is considered flammable or combustible. Cooking oils are not flammable, but once they reach their flash point and are ignited they can burn very intensely. A fire from a hot pan of grease can seem like a raging inferno. So, although they are combustible liquids rather than flammable ones, and they are not considered hazardous materials, you should consider them potentially very dangerous, indeed. The cut-off point between a flammable and combustible liquid is usually considered a flash point of 100°F (38°C), with anything under this being a flammable.
The flash point of a vegetable oil could be affected by how it is refined, and whether solvents were used. If solvent residues are left in the oil, which could be dangerous, the flash point will be lower. It would not be possible to give an accurate flash point for all types of oil, such as corn, canola, olive, peanut, sunflower, etc., but they are somewhere between 300 to 330°C (572 to 626°F). The average flash point for cooking oils is usually given as 600°F.
http://www.culinarylore.com/food-science:how-hot-before-cooking-oil-ignites
