Fire has been an important element for humans for many years, providing heat, light, and a way to cook food. It is caused by a chemical reaction called combustion where oxygen atoms combine with fuel like hydrogen and carbon to form water and carbon dioxide. The fire triangle consists of oxygen, heat, and a fuel source which are all necessary for fire to occur. Investigators use clues like burn patterns, traces of accelerants, and the appearance of burned materials to determine if a fire was accidental or arson.