What is fire? We’ve all seen fire. Probably felt it too. Fire is the rapid oxidation of a material – a process known as combustion. It is exothermic, therefore it releases heat. We also know it produces light. Lastly, we know it burns or vaporizes things.
Mechanism of fire onset:
Fire is nothing without its three components – oxidizing agent, heat and fuel. The visible part of fire is called the flame. In my previous post, I mentioned how the fascination towards colorful flames caused a severe accident. Anyway, we’ll get to the safety aspects in a while. So, fire only comes into existence when there is enough oxidizing agent (mostly oxygen), enough heat and enough fuel. When I say ‘enough’, I am trying to quantify it. What I mean is, if one of these three components is in less supply, there won’t be any fire. It also means that as long as these three components are in sufficient supply, the chain reaction that causes fire will continue and the fire will not go away.
Why do we need to extinguish fire?
We know that fire can cause loss of life, loss of property and environmental destruction. To know how fire extinguishers work therefore comes handy. For those who do not know what fire extinguishers are – fire extinguishers are red cylinders containing a certain fire extinguishing chemical inside it. In simple terms, these are devices that can contain small fires.
How do fire extinguishers work?
Fire extinguishers smother fire by:
- keeping oxidizing agent from reaching it
- replacing the oxidizing agent with an inert gas
- preventing the chain reaction (chemical reaction) that’s causing the fire to sustain itself
- absorbing the heat from the burning material
Fire extinguishing materials:
The most common and probably the most easily available fire extinguisher is water. But beware, it doesn’t work in all cases. It won’t work if the fire is caused due to, say, electronic short-circuit. It can therefore do more damage than good. OSHA (Occupational Safety and Health Administration) provides a list of common fire extinguishing materials and here they are:
- Water – removes heat
- Carbon Dioxide (CO2) – replaces oxidizing agent
- Dry Chemical – interrupts chemical reactions
- Multipurpose Dry Chemical – interrupts chemical reactions
- Halon 1301 – interrupts chemical reactions
- Halon 1211 – interrupts chemical reactions
The last two types were discontinued from use when the Montreal protocol came into effect. This is because when the two chemicals decompose, they decompose into bromine and chlorine, which then mess with the ozone layer.
Fire classes:
The tricky part of all this is knowing which fire extinguisher to use for which type of fire. Yes, there are types of fire and they are categorized into a number of different fire classes.
- Class A: Ordinary combustibles
- Class B: Flammable liquid and gas
- Class C: Electrical
- Class D: Metal
- Class K OR Class F: Cooking oils and fats (kitchen fires)
Fire classes can vary a bit according to the country you reside in. So, it is important that you first find out information specific to your own country. For example, in the UK, class B is further divided into two parts: one for liquids and another class C for gases.
Fire training:
Most laboratory and industry personnel have basic or rigorous training in fire fighting. For those who don’t have any access to such training, Wikihow can help, but only so much. You really have to get some practical knowledge – a single demonstration can someday help you save yourself or others. May be a friend from a fire fighting department can help you give a demo or one can request them to have such sessions for your entire community. Training – no training, fret not. Here’s something you can do yourself. Get to your nearest fire extinguisher, you probably know how it looks like. All you have to do now is to read what is written on it. Click here to read about how you can read the details on the cylinder and what it means in simple English. Next, go to YouTube and find videos which demonstrate how to use a fire extinguisher. Something like this video:
Further reading:
Enjoy the song. ;)
anujasawant.com 
An important topic.
Organizations (universities & companies) should offer regular (~ once a year) hands-on fire extinguisher training on a real, although small, fire.
Also, one should have a fire extinguisher at home: ours is ABC rated (Multipurpose Dry Chemical) and has its place in the kitchen. :)
After use, one has to make sure to replace a fire extinguisher with a new/completely filled one. There is a story to tell about that. :)
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