Fire. It's an element that has the potential to help and destroy at the same time. To understand fire, one must realize it is the result of a combustion reaction--rapid oxidation of fuel with the addition of heat and light. Slow oxidation would occur rusting, whereas fast oxidation occurs detonations and explosions, like bombing and fireworks. For combustion to occur, four components must be present: oxygen, fuel, heat, and a self-sustained chemical reaction, otherwise known as a chain reaction. Without just one of these four components, combustion will not occur. The fuel used to start a fire has a chemical that will bond with oxygen, for it is found in air. Fuel can be solid, liquid, or gaseous; for solid fuels, pyrolysis, the decomposition of a susbtance through heat, occurs. Products of water vapor, carbon dioxide, charcoal, and various vapors are results of pyrolysis, depending on the temperature of the reaction. 

There are three phases of fire: the incipient, or growth, phase; the free-burning, or fully developed, phase, and the smoldering, or decay, phase. In the incipient phase, the fire produces water vapor, carbon dioxide, and other gases such as carbon monoxide and sulfur dioxide in small quantities. This is because the oxygen in air has not been reduced significantly; heat is building at this point, and will keep increasing. In the free-burning phase, the temperature of the fire is the hottest; firefighters must use protective gear and masks, or they risk lung and skin damage when attempting to extinguish the flame. Convection occurs here, as the fire quickly draws in more oxygen and carries the heat to confined areas. Lastly, int he smoldering phase, there is little to no flame, as glowing embers appear and continuously burn.