Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain stuff,
Speaker 1: it's Christian Seger. Let's talk about fire. Fire is the
Speaker 1: result of a chemical combustion reaction, typically between oxygen and
Speaker 1: some sort of fuel like wood or gasoline. For the
Speaker 1: reaction to occur, the fuel has to reach its ignition temperature.
Speaker 1: For wood, that's about five hundred degrees fahrenheit or two
Speaker 1: hundred and sixty degrees celsius. The heat decomposes some of
Speaker 1: the woods cellulose, and the decomposed stuff is released as
Speaker 1: volatile gases, like a compound of hydrogen, carbon, and oxygen.
Speaker 1: When the gas is hot enough, its molecules break apart.
Speaker 1: The atoms recombine with the oxygen to form water, carbon dioxide,
Speaker 1: and other products. The heat keeps the fuel at the
Speaker 1: ignition temperature, so it keeps burning as long as there
Speaker 1: is fuel and oxygen. So there you have it. Fire,
Speaker 1: the result of extreme heat, oxygen, and fuel. But what
Speaker 1: about fire extinguishers? They remove at least one of these
Speaker 1: elements from the equation. Fire extinguishers are metal cylinders filled
Speaker 1: with water or smothering material, and when you depress a
Speaker 1: lever at the top, the material is expelled by high pressure,
Speaker 1: kind of like an aerosol. Can imagine a fire extinguisher
Speaker 1: cut in half. Okay, that plastic siphon tube leads from
Speaker 1: the bottom of the fire suppressant reservoir to the top
Speaker 1: of the extinguisher. A spring mounted valve blocks the passageway
Speaker 1: from the siphon to the nozzle, and at the top
Speaker 1: of the cylinder there is a smaller cylinder filled with
Speaker 1: compressed gas liquid carbon dioxide. For example, A release valve
Speaker 1: keeps the compressed gas from escaping. When you pull out
Speaker 1: the safety pin and depress the operating lever, it pushes
Speaker 1: on an actuating rod. The rod presses the spring mounted
Speaker 1: valve down to open up the passage to the nozzle.
Speaker 1: The bottom of the actuating rod has a sharp point
Speaker 1: which pierces the gas cylinder release valve. The compressed gas escapes,
Speaker 1: applying downward pressure on the fire suppressant material. This drives
Speaker 1: the material up the siphon and out the nozzle. The
Speaker 1: proper way to use the extinguisher is to aim it
Speaker 1: directly at the fuel, not the flames, and spray in
Speaker 1: a sweeping motion. There are three main types of extinguisher.
Speaker 1: A water extinguisher can put out things like burning wood, paper,
Speaker 1: or cardboard, but it doesn't work well on electrical fires
Speaker 1: or fires involving inflammable liquids. In an electrical fire, water
Speaker 1: may conduct the current, which could electrocute you. Water will
Speaker 1: only spread an inflammable liquid, making the fire worse. Then
Speaker 1: there's the carbon dioxide extinguisher. The CO two is kept
Speaker 1: in a pressurized liquid form. When the container is opened,
Speaker 1: the CO two forms a gas. This gas is heavier
Speaker 1: than oxygen, so it deplaces the oxygen surrounding the fuel.
Speaker 1: This extinguisher is common in restaurants because it won't contaminate
Speaker 1: cooking equipment or food. The most popular extinguisher material is
Speaker 1: the dry chemical extinguisher. These cylinders contain foam or powder,
Speaker 1: typically made of sodium bi carbonate also known as baking soda,
Speaker 1: potassium bicarbonate, or mono ammonium phosphate. Baking soda starts to
Speaker 1: decompose at only a hundred and fifty eight degrees fahrenheit
Speaker 1: or seventy degrees celsius, and when it decomposes, it releases
Speaker 1: c O two. The c O two, along with the
Speaker 1: insulation of the foam, smothers fire. The best way to
Speaker 1: tell which fire extinguisher you have and which fires it's
Speaker 1: best suited to fight is to look at the rating.
Speaker 1: All fire extinguishers have an A, B or C rating.
Speaker 1: A Class A fire extinguisher works best against fires involving paper, wood, plastic,
Speaker 1: and textiles. A Class B fire extinguisher can put out
Speaker 1: flammable liquid fires you know, things like cooking oil, gasoline, paint,
Speaker 1: or oil, and a Class CE extinguisher is your go
Speaker 1: to for live electrical fires. Each extinguisher will have a
Speaker 1: number by the letter indicating the size of the fire
Speaker 1: that it can tackle, But please be careful. Most fire
Speaker 1: extinguishers contain a small amount of suppressing. You can use
Speaker 1: it up in seconds. That's why they're only effective on
Speaker 1: relatively small fires. To put out a bigger fire, you
Speaker 1: need more equipment like a fire engine, as well as
Speaker 1: trained professionals. But for the blazes that can pop up
Speaker 1: in your house, a fire extinguisher can be a lifesaver.
Speaker 1: Check out the brainstuff channel on YouTube, and for more
Speaker 1: on this and thousands of other topics, visit how stuff
Speaker 1: works dot com.