What is a fire triangle?

A fire triangle is a model that helps explain the necessary components for fire to ignite and sustain itself. The correct components are heat, fuel, and oxygen.

Heat is required to raise the materials involved to their ignition temperature, which is the point at which they can catch fire. Fuel is any combustible material, ranging from wood and paper to gasoline or other flammable substances. Oxygen is essential because fire needs it to support the chemical reaction of combustion. In typical atmospheric conditions, there is enough oxygen (approximately 21%) to sustain combustion.

Each of the other answer options includes elements that are not involved in the basic fire triangle. For instance, carbon dioxide, smoke, and nitrogen do not contribute to the fire's ability to ignite and burn in the same way heat, fuel, and oxygen do. Thus, the combination of heat, fuel, and oxygen is what constitutes the foundation for understanding how fires start and how they can be extinguished by removing one or more of these essential elements.