E2.2 The ignition of solids, liquids, and gases Assessment criteria: E2.1-E2.3: Describe the principles of combustion in relation to fire safety.
Definitions Flash point
A liquid is classified as flammable or combustible depending on its flash point. In the UK, a flammable liquid has a flash point below 55°C, while a Highly Flammable liquid has a flash point less than 21°C, and an Extremely Flammable is one with a flash point less than 0°C and a boiling point of 35°C. Definitions may vary globally. For example, the US and Canada classify a combustible liquid as one with a flash point above 37.8 0 C and below 93.3 0 C and a flammable liquid with a flash point < 37.8 0 C. The flash point of a fuel is ‘the lowest temperature at which the vapour given off by a substance can be momentarily ignited in the air’. As a further explanation, it is the temperature when the vapour pressure of a substance becomes high enough to allow the air or vapour layer over the substance to be ignited. It is worth pointing out that some flash points may vary from country to country. Certain substances, such as Ether and Acetone have flash points below room temperature, which makes them very dangerous. For example, no additional heat needs to be applied to the fuel source for the flash point to be reached. The lower the flash point, the greater the potential fire hazard. Fire point
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