The elements required for a fire to start are

The elements required for a fire to start are oxidizing agent, heat, and fuel.

The oxidizing agent is usually oxygen - when there is a lot of air, of oxygen, a fire can broke out more easily if the conditions are right - if there is no oxygen, the fire won't start - we put out a fire by depriving it of oxygen. Next, you need some heat and fuel to start a fire, which can all be seen in this triangle.

Heat, Fuel, and Oxidizing agent