Some solids may exhibit smoldering which is glowing combustion on the surface of the material. Combustion that occurs in confinement with the subsequent generation of pressure will result in an explosion. For example, flammable gases that are premixed with oxygen upon ignition will expand and result in considerable pressure. If confined, they may explode the container. The combustible material must be heated to its ignition temperature before it will support combustion or the spread of flames.
Fire control is based on achieving some or all of the above conditions.
As a special note, with the advent of synthetic materials, a fourth element has been added which is the combined effects of combustible products. This chemical reaction is considered another component of burning and is represented by a tetrahedron or pyramid-like figure. As previously mentioned, fire is a chemical reaction known as combustion which is the rapid chemical combination of fuel with oxygen that releases heat and light. Sources of heat are open flames, the sun, hot surfaces, sparks, friction, electrical energy, and compression of gasses. Many sources of fuel are present in numerous offices and departments on campus.