The flash point of a fuel is the temperature at which it gives off enough flammable vapours to ignite when a source of ignition, like an open flame, is introduced. This should not be confused with the fire point, which is the temperature at which the vapours of the fuel will continue to burn once the source of ignition is removed, usually for a minimum of five seconds. A third point, the autoignition temperature, should also not be confused with the first two. The autoignition temperature is the temperature at which the fuel will spontaneously ignite without the need for a spark, flame, or any other ignition source.
Understanding flash points and auto-ignition temperatures is vital if you work in the fuel industry, or in an industry that utilises industrial amounts of fuel. This is because some fuels – like kerosene – have a flash point that’s within the normal temperature ranges of some places on earth. This means, if you live in a hot region like Australia, North Africa, or the Middle-East, kerosene fuel may be more volatile and will ignite far more easily than it would in Northern Europe, North America, or Russia.
Let’s take a look at some of the common fuels in the industry and what their flash points and autoignition temperatures are:
Petrol and Diesel
Petrol (gasoline) has a fairly low flashpoint at −43 °C (−45 °F). This means that, unless you’re in one of the coldest places in the world, your petrol fuel is above its flashpoint. White Diesel, on the other hand, enjoys a mid-range flash point of over 52 °C (126 °F), meaning the exact opposite! Diesel will likely be below its flash point unless you are in a particularly hot place.
Both petrol and diesel have quite high autoignition temperatures, or our vehicles would be in trouble! Petrol and diesel have autoignition temperatures of 280 °C (536 °F) and 210 °C (410 °F), respectively.
