Final answer:
For a fire to occur, three elements are essential: fuel, an ignition source, and an oxidizer such as oxygen.
Step-by-step explanation:
The three elements that are necessary for a fire to occur are: Fuel, an ignition source, and an oxidizer (typically oxygen). Fuel serves as a combustible material that is characterized by its properties such as moisture content, size, shape, and how it is arranged.
An ignition source such as heat or a flame is responsible for the initial ignition and maintaining the fire. Lastly an oxidizer is required for the chemical reaction of combustion; in most cases, this is oxygen from the air, which makes up about 21% of our atmosphere. Without any one of these elements a fire cannot be sustained.