A fire is caused by sufficient levels of fuel, heat and oxygen existing simultaneously. Fuel is anything that burns, such as wood, paper and flammable solvents and chemicals. Air contains about 21 percent oxygen, and most fires require at least 16 percent oxygen content to burn. Heat comes from many sources.
Fires can be extinguished by cooling them (removing the heat), smothering them (removing the oxygen) or isolating them (removing the fuel).
