The oxidizer is the other reactive element in the chemical reaction.
In most cases it is the ambient air, and in particular one of its components: oxygen.
By depriving a fire of air, we can extinguish it; for example, when covering the flame of a small candle with an empty glass, fire stops;
to the contrary, if we blow on a wood fire, we can activate it (by providing more air).
In certain torches, the presence of oxygen improves combustion.
In very particular cases (often with explosives such as aluminum), the oxidizer and the combustible are the same (as for nitroglycerin, an instable molecule
made of one oxidizing part linked to a reducing part).
The reaction is initiated by an activating energy, in most cases, heat.
Friction for example, in case of matches, heating electrical wire, flames (propagation of fire),
sparks (from a lighter or any electrical device).
There are many other ways to bring sufficient activation energy such as: electricity, radiation, and pressure …
which will all lead to a rise in temperature.
In most cases, heat production enables self-sustainability of the reaction, or even growth into a chain reaction.
The temperature at which a liquid produces a sufficient amount of vapor to form an ignitable mixture in air is called the flash-point.
