Because Fuel (the gas vapors) in the area came in contact with a very hot surface on the light and ignited the vapors. Since different types of Fuel can be ignited at different temperatures, it’s important to know more about the flammability levels of the Fuels in the different Groups, and also – to know how hot a light fixture can get.This brings us back to the Groups of materials covered in earlier Journals. These Groups are determined in part by a material’s explosiveness and by its
And one key measure of a Group’s flammability is the temperature at which a Group’s material ignites.
Every Fuel listed in Classes I, II and III has a different temperature where they will start to burn. Technically, this is called
spontaneous ignition temperature
(or AIT, auto ignition temperature) at which temperature it will ignite spontaneously.