Definition - What does Flash Point mean?
A flash point is the lowest temperature at which a combustible liquid vaporizes, mixes with the adjacent air and ignites if suitably initiated by an ignition source such as hot substance, spark or flame. Ignition source is an essential for measuring a flash point and the burning ceases as soon as the ignition source is removed (contrary to auto ignition, which does not require any ignition source).
Safeopedia explains Flash Point
Flash point of any liquid indicates how easy it is to ignite the said liquid. The lower the flash point of any liquid, the easier it is to ignite. Gasoline’s flash point is minus (-) 40°C and diesel’s flash point is (+) 62°C. It is therefore much easy, to ignite gasoline than diesel. Liquids those have lower flash points are more flammable and extremely fire hazard.
Liquids and chemicals used in industries need to be categorized as per their potential level of fire hazard. Flash point is one of the major considerations for deciding which flammable class a particular liquid or chemical belongs to. Flash point can be measured in two ways, open cup and closed cup. In an open cup method, a flame is brought to the surface of the liquid held in an open cup. In a closed cup method, the cup containing liquid is sealed with a lid and ignition source is introduced through the lid in equilibrium or non-equilibrium condition.