Final answer:
A fire is caused by a combination of oxygen, fuel, and heat, also known as the 'fire triangle'. Oxygen supports the chemical reactions, fuel provides a combustible material, and heat is the ignition source that also sustains and spreads the fire.
Step-by-step explanation:
What causes a fire? The answer is oxygen, fuel, and heat. These three elements are essential for a fire to occur. Oxygen is a key component of the air we breathe, and in the context of a fire, it supports the chemical reactions that happen during combustion. Fuel can be any combustible material with varying moisture content, size, shape, and quantity, which determines how readily it will burn. Heat serves as the initial ignition source and also helps to maintain and spread the fire by drying out nearby fuel and warming the surrounding air. This combination of elements is sometimes referred to as the 'fire triangle.'
For example, when methane burns in the presence of oxygen, the chemical reaction produces carbon dioxide, water, heat, and sometimes other by-products like carbon monoxide if the oxygen supply is limited. This reaction is exothermic, meaning it releases energy in the form of heat, which further perpetuates the combustion process.