BASIC PRINCIPLES OF FIRE. There are commonly three entities which are necessary for the ignition of the fire:- • Fuel – a combustible material or substance that is consumed during the combustion process. In a typical workplace, fuels can include paper and cardboard, wood and soft furnishings, structural materials, petrol and diesel fuels, butane, acetylene and other gases, solvents and other chemicals. • Oxygen – consumed during combustion when it is chemically combined with the fuel. Oxygen is present in air at a concentration of 21%. During a fire oxygen can also come from other sources, including certain oxygen-rich chemicals (usually called oxidising agents), such as ammonium nitrate. • Sources of ignition (heat) – a heat or ignition source is essential to start the combustion process. Once combustion has started it generates its own heat which is usually sufficient to keep the fire bur...