An oxidizer (or oxidizing agent) is defined as a compound which is capable of accepting electrons in a chemical reaction. The oxidizer (or oxidizing agent) is thus "reduced" and a fuel (or the reducing agent) is oxidized as it looses electrons.

The reaction is exothermic and the gases produced expand rapidly. The reaction essentially releases all of the energy that was stored in the fuel as heat and pressure. To initiate the reaction between oxidizers and fuels that are commonly found in blasting agents, a strong pulse of energy is required. This energy can be supplied by source which ignites, provides an electric current or small explosion.