The primary element required for fire is oxygen. Fire is a chemical reaction known as combustion, which occurs when a fuel reacts rapidly with oxygen, producing heat, light, carbon dioxide, and water. While fuels can vary, the presence of oxygen is crucial, as it supports the oxidation process. This is why fire can be extinguished by cutting off its oxygen supply, a principle used in fire-fighting techniques. The classic fire triangle—fuel, heat, and oxygen—demonstrates these essential components for sustained combustion.