Final answer:
A fire requires four elements known as the fire tetrahedron: heat, fuel, oxygen, and a chemical chain reaction. These elements are crucial for ignition and sustaining a fire.
Step-by-step explanation:
The four components that must be present for a fire to occur are commonly known as the fire tetrahedron. This includes: heat, fuel, oxygen, and a chemical chain reaction.
Heat provides the necessary energy to start and sustain a fire. Fuel, which can be any kind of combustible material, is what the fire consumes to sustain itself. Oxygen, present in air at approximately 21 percent, is necessary to support the combustion process.
And finally, a chemical chain reaction occurs as the fuel burns and reacts with oxygen, producing the heat and light we see as fire. Without any one of these components, a fire cannot start or continue to burn.