Combustion is a chemical reaction that involves the oxidation of a fuel by an oxidizing agent, with the development of heat and electromagnetic radiation, often including light radiation.
The “fire triangle” consists of the three elements that are necessary for the combustion reaction to take place. These three elements are:
fuel: it is the substance that is oxidized in the combustion process. It can be of various types, for example: hydrocarbons, timber or coal;
oxidizer: a substance that acts as an oxidizing agent of a fuel in a combustion reaction. The oxidizer par excellence is oxygen present in the air, but other substances can also act as oxidisers (eg. Ozone, hydrogen, etc.);
trigger: the reaction between the fuel and the comburent is not spontaneous but occurs by an external trigger. The trigger can be represented for example by a heat source or a spark. The trigger represents the activation energy necessary for the reactant molecules to start the reaction and must be supplied from the outside. Subsequently, the energy released by the reaction itself makes self-sustenance possible, without further external energy inputs.