Well, perhaps I should give the literal
explanation of how this is accomplished...
Disclaimer: Fire fighting is not something to be taken lightly. Most firefighters go through around 500 hours of training. Don't try this at home (and don't blame me if you do).
First, some background. Fire is a chemical reaction consisting of three basic elements: heat, fuel, and oxygen, also known as the fire triangle1. The concept behind putting out a fire is to remove one of these three sides, which will make the hot stuff go away. In order to remove one of these sides, it is necessary to understand each of them a little more in depth.
Perhaps the easiest to explain. Removing the oxygen supply will quickly suppress the fire. This can be seen by lighting a candle, then covering it with a jar. Note that the flame slowly dies down as the oxygen supply is depleted. This is also used in small brush fires using a tool known as a flapper. The flapper is basically a square of thick rubber or other material attached to a stick that the firefighter places over the fire and steps on to remove the oxygen from the fire. It is also the concept behind Halon systems (a good reason to leave the room when that system is activated).
One of the most important aspects of fire. This is the stuff that burns, or that is destroyed by the fire itself. It can be anything from paper to magnesium. Fuel is broken down into four sub-categories (labled 'A','B','C' and 'D' classes) that can be seen on the side of fire extinguishers:
An example of using the tactic
of removing fuel to put out a fire is a wildland fire
. In wildland fires, the firefighter
s will burn trees and grasses ahead of the fire so that when the fire reaches the burned area it will have no fuel to burn and go out.
"Put the wet stuff on the red stuff"
This is what most people think of when they see fires and fire trucks. And yes, big fires require big water. We carry on our truck a master stream capable of flowing 1500 gallons a minute (Quick math: 1 gal of H2O = ~8lbs = ~12000 lbs of water a minute). The concept here is to cool the fuel past the point of combustion. This method is highly ineffective on most fires. In reality, when we use water, it is for the oxygen removing effect, not the cooling effect. The reason for this is that the steam from water conversion ratio is 1700:1 (meaning 1700 gallons of steam will be created at 100 C for each 1 gallon of water). This steam pushes all of the oxygen out of the area, effictively smothering the fire.
Tips for putting out fires
- First and foremost: CALL THE FIRE DEPARTMENT BEFORE ATTEMPTING TO PUT OUT THE FIRE! If you wait to call, by the time you do call, the fire will be too large, and will cause much damage by the time we get there. Rememeber, you can always cancel us, and we have no problem pulling up and the fire being out, as opposed to you being trapped inside.
- Aim for the base of the fire. Regardless of the extinguishing agent you are using. The only exception to this is flashover/rollover situations which if you are experiencing, umm, hope you followed that first warning.
- P.A.S.S. for extinguishers. That is, Pull (the pin), Aim (at the base of the fire), Spray (the extinguisher, pull the trigger!), and Sweep (side to side, keeping aimed at the base of the fire)
Finally, please please please DO NOT GO BACK INSIDE A BURNING STRUCTURE
FOR ANY REASON. Yes, I know your cat
is in there, or your papers, or maybe even your kid or family member
. Life is much easier for us
if we only have to search for one victim
than for that victim, plus the person who went in to save them, plus the person who went in to save the second person, etc.
Subnote 1: There is some dispute as to whether the term 'fire triangle
' is appropriate. Some people will argue that the chemical reaction
of burning should be a side, etc, etc. Theoretically, you could end up with a 16-side object
, but the triangle
is the most widely recognized and easy to understand.
Subnote 2: Don't, don't, don't put water on a flammable liquid fire. You will simply spread the fire. For grease fires, keep baking soda around, or put the lid on the pan.
Subnote 3: Generally, if you kill the power to a Class C fire, it becomes a class A or class D fire.
Subnote 4: Don't, don't, don't put water on a flammable metal fire unless you have a LOT of water to use. Engine fires in old VW Bugs have this issue because of the amount of magnesium in them. Generally removal of oxygen is the perferred method in this case.