Welcome to brain Stuff from How Stuff Works. Hey, brain stuff, it's Christian Seger. Let's talk about fire. Fire is the result of a chemical combustion reaction, typically between oxygen and some sort of fuel like wood or gasoline. For the reaction to occur, the fuel has to reach its ignition temperature. For wood, that's about five hundred degrees fahrenheit or two
hundred and sixty degrees celsius. The heat decomposes some of the woods cellulose, and the decomposed stuff is released as volatile gases, like a compound of hydrogen, carbon, and oxygen. When the gas is hot enough, its molecules break apart. The atoms recombine with the oxygen to form water, carbon dioxide, and other products. The heat keeps the fuel at the ignition temperature, so it keeps burning as long as there is fuel and oxygen. So there you have it. Fire,
the result of extreme heat, oxygen, and fuel. But what about fire extinguishers? They remove at least one of these elements from the equation. Fire extinguishers are metal cylinders filled with water or smothering material, and when you depress a lever at the top, the material is expelled by high pressure, kind of like an aerosol. Can imagine a fire extinguisher cut in half. Okay, that plastic siphon tube leads from the bottom of the fire suppressant reservoir to the top
of the extinguisher. A spring mounted valve blocks the passageway from the siphon to the nozzle, and at the top of the cylinder there is a smaller cylinder filled with compressed gas liquid carbon dioxide. For example, A release valve keeps the compressed gas from escaping. When you pull out the safety pin and depress the operating lever, it pushes on an actuating rod. The rod presses the spring mounted valve down to open up the passage to the nozzle.
The bottom of the actuating rod has a sharp point which pierces the gas cylinder release valve. The compressed gas escapes, applying downward pressure on the fire suppressant material. This drives the material up the siphon and out the nozzle. The proper way to use the extinguisher is to aim it directly at the fuel, not the flames, and spray in a sweeping motion. There are three main types of extinguisher.
A water extinguisher can put out things like burning wood, paper, or cardboard, but it doesn't work well on electrical fires or fires involving inflammable liquids. In an electrical fire, water may conduct the current, which could electrocute you. Water will only spread an inflammable liquid, making the fire worse. Then there's the carbon dioxide extinguisher. The CO two is kept in a pressurized liquid form. When the container is opened,
the CO two forms a gas. This gas is heavier than oxygen, so it deplaces the oxygen surrounding the fuel. This extinguisher is common in restaurants because it won't contaminate cooking equipment or food. The most popular extinguisher material is the dry chemical extinguisher. These cylinders contain foam or powder, typically made of sodium bi carbonate also known as baking soda,
potassium bicarbonate, or mono ammonium phosphate. Baking soda starts to decompose at only a hundred and fifty eight degrees fahrenheit or seventy degrees celsius, and when it decomposes, it releases c O two. The c O two, along with the insulation of the foam, smothers fire. The best way to tell which fire extinguisher you have and which fires it's best suited to fight is to look at the rating. All fire extinguishers have an A, B or C rating.
A Class A fire extinguisher works best against fires involving paper, wood, plastic, and textiles. A Class B fire extinguisher can put out flammable liquid fires you know, things like cooking oil, gasoline, paint, or oil, and a Class CE extinguisher is your go to for live electrical fires. Each extinguisher will have a number by the letter indicating the size of the fire that it can tackle, But please be careful. Most fire extinguishers contain a small amount of suppressing. You can use
it up in seconds. That's why they're only effective on relatively small fires. To put out a bigger fire, you need more equipment like a fire engine, as well as trained professionals. But for the blazes that can pop up in your house, a fire extinguisher can be a lifesaver. Check out the brainstuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com.