Causes of Chemical Fires
What is a Chemical Fire?
A chemical fire is any flame that begins due to a chemical reaction that ignites a solid, liquid, or gas chemical compound. Just as run-of-the-mill fires can be extremely destructive, chemical fires are incredibly dangerous, able to cause severe and fatal burns, and destroy most living or material things that stand in their way. In order to properly defend against chemical fires, it is crucial to understand how they start and stay burning.
The Chemistry Behind Them:
First of all, let's talk about what causes a normal fire. Fire operates under a paradigm appropriately known as the fire triangle. The triangle is a simple model that examines which physical laws govern the environmental interactions that, in turn, spark the production of a flame. Three components must interact with each other in order to create a flame (hence, the triangle name); fuel, oxygen, and heat.
- Fuel: Some sort of combustible element is required to act as the ignition source of the fire, as well as to keep it burning. A fire will die most often because of a lack of fuel, either because it consumed all the available fuel in the environment, or because the fuel was mechanically or chemically removed in an attempt to douse the flame. We usually think of wood or paper as the fuel for our fires, but in a chemical fire, any flammable solid, liquid, or gas chemical can act as the fuel.
- Oxygen: An oxidizer, usually oxygen, is needed to react with the fuel in order for a fire to begin and continue. The less concentration of oxygen available, the slower the fuel will combust, since there is less for the fuel to react with. This is why a lit candle will go out if a glass is placed over it.
- Heat: In order to start a fire, the fuel and oxygen reacting with each other must exceed a threshold called the flash point. The flash point is the temperature at which the chemical reaction can combust, producing a flame. Different chemicals have different flash points, some relatively high, and some incredibly low. The lower the flash point of a compound, the more easily that compound ignites.
If you're unsure of the danger chemical fires can pose, this video should clear things up.
The Danger of Chemical Fires:
Aside from the obvious burning, chemical fires also are quite likely to explode, depending on the chemicals in question. This can lead to injuries from the heat, the shockwaves emitted by the explosion, the resulting smoke, and any debris sent hurling.
Which Chemicals Start Them?
Although there are many more flammable chemicals than one can list, below are descriptions of a few of the most commonly seen sources of chemical fires;
- Azides: These can be very dangerous when mixed with heavy chemicals such as lead or copper. They degrade quickly when exposed to heat, given them explosive potential.
- Ether: A very common, highly flammable and potentially explosive compound found in anesthetics, refrigerants, and alcohol. Ethers have low flash points,below 73 degrees f Fahrenheit, meaning it doesn't take much heat to set them off.
- Gasoline: Gasoline is a mixture of approximately 150 different chemicals, many of them flammable. This makes gasoline vapors extremely dangerous when close to heat sources. Gasoline is incredibly volatile and explosive.
- Glycerol: This chemical has widespread use in pharmaceuticals and is combustible at about 140 degrees F.
- Perchloric Acid: Perchloric acid is a laboratory reagent that can ignite when in contact with products containing cellulose (plant products) like wood and paper.
- Picric Acid: Also a reagent, picric acid is mainly used in solid form and detonates when struck, rubbed, or heated.
- Petroleum: At the base of gasoline, diesel, kerosene, and really every other oil product lies petroleum. Depending on the product the petroleum is used in, the volatility may vary, but care should be taken when handling any petroleum product.
How to Avoid/Extinguish Chemical Fires:
Each element of the fire triangle is as pivotal as the others. That being said, if one of these elements is removed from the reaction, whether is be fuel, oxygen, or heat, the fire will not be able to continue. The most effective way to extinguish a small chemical fire (or any fire for that matter) yourself is to use a dry fire extinguisher. Most home come equipped with these handy devices, capable of choking the flame by replacing the oxygen around it with carbon dioxide, which the flame cannot react with. Be sure to read the directions on the fire extinguisher carefully, hopefully before a fire starts! Water can be dangerous for use in chemical fires, as the steam resulting from evaporation may actually accelerate the temperature rise. For larger flames, don't hesitate to call the fire department. A quick response could mean the difference between some singed carpet and a burned down home.
Of course, it's preferable to avoid starting a chemical fire in the first place. The best way to do so is to carefully follow the directions on any containers of chemicals you may be using. Be sure to store them in cool, dry places, don't mix the chemicals, and do not use in a situation where they will be subjected to high temperatures.