How Fires Burn
What a Fire Needs to Burn:
A fire requires four elements to continue burning: oxygen, heat, fuel, and an uninhibited chemical chain reaction. When any of these elements is removed, combustion ceases to take place.
The combustion reaction in a fire releases the energy from chemical bonds in the form of heat and radiant (light) energy. The reaction is usually initiated by the addition of heat, but quickly begins to generate enough heat to feed itself on its own energy. This is why fires rapidly grow to uncontrollable proportions. A fire will double every minute that it is left freely burning.
A Typical Combustion Reaction:
Most combustible materials contain carbon and hydrogen. When oxygen and heat are added, the combustion reaction occurs. In an ideal combustion reaction, the only reactants are: carbon, hydrogen, and heat; and the only products are: carbon dioxide, water, and energy. A typical reaction would look like this:
C5H12 + 8O2 + Heat → 5CO2 + 6H2O + More Heat/Light
In a real fire, however, there are other substances besides carbon, hydrogen, and oxygen, and other vapors and particles can be released into the air. When there is not enough oxygen for clean burning, incomplete combustion occurs, producing free carbon atoms and carbon monoxide molecules.
Carbon atoms scatter light from the orange portion of the visible spectrum, giving fire its characteristic color. Very clean, hot fires can sometimes appear to have no color at all, because all of their carbon molecules have been paired with oxygen.
Carbon monoxide is a colorless, odorless gas that is very toxic to humans. It bonds with the hemoglobin (oxygen carrying molecule) in red blood cells in the same manner that oxygen would. This prevents the uptake of oxygen by red blood cells, and can eventually lead to asphyxiation. Since carbon monoxide is not only produced by fire, carbon monoxide detectors have been installed in many homes to prevent related fatalities.
Fire Hazards
Below is a list of common household and work related fire hazards.
Electrical hazards: overloaded or old fuses, frayed wiring, poor ground connections, static electricity
Chemical Hazards: Flammable liquids/vapors, spontaneous combustion of oily rags, weak fuel pipes
Poor house keeping: smoking, children playing with matches, exposed lights/heaters in contact with combustible materials, stoves/appliances left on without supervision.