WEBVTT - BrainStuff Classics: How Do Fire Extinguishers Work?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,

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<v Speaker 1>I'm Lauren Vogelbaum, and this is a classic episode from

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<v Speaker 1>our previous host, Christian Sager. The fire extinguisher is an

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<v Speaker 1>amazing piece of simple equipment that can help you smother

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<v Speaker 1>of fire should it happen to get a little out

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<v Speaker 1>of control. In this episode, we explain how they work

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<v Speaker 1>and what kinds work for what kinds of fires. Hey,

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<v Speaker 1>brain Stuff, it's Christian Sager. Let's talk about fire. Fire

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<v Speaker 1>is the result of a chemical combustion reaction, typically between

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<v Speaker 1>oxygen and some sort of fuel like wood or gasoline.

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<v Speaker 1>For the reaction to occur, the fuel has to reach

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<v Speaker 1>its ignition temperature. For wood, that's about five hundred degrees

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<v Speaker 1>fahrenheit or two hundred and sixty degrees celsius. The heat

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<v Speaker 1>decomposes some of the woods cellulose, and the decomposed stuff

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<v Speaker 1>is released as volatile gases, like a compound of hydrogen, carbon,

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<v Speaker 1>and oxygen. When the gas is hot enough, its molecules

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<v Speaker 1>break apart. The atoms recombine with the oxygen to form water,

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<v Speaker 1>carbon dioxide, and other products. The heat keeps the fuel

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<v Speaker 1>at the ignition temperature, so it keeps burning as long

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<v Speaker 1>as there is fuel and oxygen. So there you have it.

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<v Speaker 1>Fire the result of extreme heat, oxygen and fuel. But

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<v Speaker 1>what about fire extinguishers They remove at least one of

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<v Speaker 1>these elements from the equation. Fire extinguishers are metal cylinders

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<v Speaker 1>filled with water or smothering material, and when you depress

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<v Speaker 1>a lever at the top, the material is expelled by

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<v Speaker 1>high pressure, kind of like an aerosol. Can imagine a

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<v Speaker 1>fire extinguisher cut in half. Okay, that plastic siphon tube

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<v Speaker 1>leads from the bottom of the fire suppressant reservoir to

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<v Speaker 1>the top of the extinguisher. A spring mounted valve blocks

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<v Speaker 1>the passageway from the siphon to the nozzle, and at

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<v Speaker 1>the top of the cylinder there is a smaller cylinder

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<v Speaker 1>filled with compressed gas liquid carbon dioxide for example. A

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<v Speaker 1>release valve keeps the compressed gas from escaping. When you

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<v Speaker 1>pull out the safety pin and depress the operating lever,

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<v Speaker 1>it pushes on an actuating rod. The rod presses the

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<v Speaker 1>spring mounted valve down to open up the passage to

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<v Speaker 1>the nozzle. The bottom of the actuating rod has a

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<v Speaker 1>sharp point which pierces the gas cylinder. Release valve. The

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<v Speaker 1>compressed gas escapes applying downward pressure on the fire suppressant material.

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<v Speaker 1>This drives the material up the siphon and out the nozzle.

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<v Speaker 1>The proper way to use the extinguisher is to aim

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<v Speaker 1>it directly at the fuel, not the flames, and spray

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<v Speaker 1>in a sweeping motion. There are three main types of extinguisher.

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<v Speaker 1>A water extinguisher can put out things like burning wood, paper,

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<v Speaker 1>or cardboard, but it doesn't work well on electrical fires

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<v Speaker 1>or fires involving inflammable liquids. In an electrical fire, water

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<v Speaker 1>may conduct the current, which could electrocute you. Water will

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<v Speaker 1>only spread an inflammable liquid, making the fire worse. Then

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<v Speaker 1>there's the carbon dioxide extinguisher. The CEO two is kept

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<v Speaker 1>in a pressurized liquid form. When the container is opened,

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<v Speaker 1>the CO two forms a gas. This gas is heavier

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<v Speaker 1>than oxygen, so it deplaces the oxygen surrounding the fuel.

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<v Speaker 1>This extinguisher is common in restaurants because it won't contaminate

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<v Speaker 1>cooking equipment or food. The most popular extinguisher material is

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<v Speaker 1>the dry chemical extinguisher. These cylinders contain foam or powder,

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<v Speaker 1>typically made of sodium bi carbonate, also known as baking

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<v Speaker 1>soda potassium bicarbonate or mono ammonium phosphate. Baking soda starts

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<v Speaker 1>to decompose at only a hundred and fifty eight degrees

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<v Speaker 1>fahrenheit or seventy degrees celsius, and when it decomposes, it

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<v Speaker 1>releases c O two. The CEO two, along with the

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<v Speaker 1>insulation of the foam, smothers fire. The best way to

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<v Speaker 1>tell which fire extinguisher you have and which fires it's

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<v Speaker 1>best suited to fight is to look at the rating.

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<v Speaker 1>All fire extinguishers have an A, B or C rating.

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<v Speaker 1>A Class A fire extinguisher works best against fires involving paper, wood, plastic,

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<v Speaker 1>and textiles. A Class B fire extinguisher can put out

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<v Speaker 1>flammable liquid fires, you know, things like cooking oil, gasoline, paint,

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<v Speaker 1>or oil, and a Class C extinguisher is your go

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<v Speaker 1>to for live electrical fires. Each extinguisher will have a

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<v Speaker 1>number by the letter indicating the size of the fire

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<v Speaker 1>that it can tackle. But please be careful. Most fire

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<v Speaker 1>extinguishers contain a small amount of suppressant. You can use

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<v Speaker 1>it up in seconds. That's why they're only effective on

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<v Speaker 1>relatively small fires. To put out a bigger fire, you

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<v Speaker 1>need more equipment. Like a fire engine as well as

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<v Speaker 1>trained professionals, but for the blazes that can pop up

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<v Speaker 1>in your house, a fire extinguisher can be a life sapor.

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<v Speaker 1>Today's episode was written by Ben Boland and produced by

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<v Speaker 1>Tyler Clang. For more on this and lots of other topics,

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<v Speaker 1>visit how stuffworks dot com. Brain Stuff is a production

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<v Speaker 1>of I Heart Radio. For more podcasts on my heart Radio,

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<v Speaker 1>visit the i heart Radio app, Apple Podcasts, or wherever

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<v Speaker 1>you listen to your favorite shows.