1 00:00:02,040 --> 00:00:07,120 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain stuff, 2 00:00:07,160 --> 00:00:10,680 Speaker 1: it's Christian Seger. Let's talk about fire. Fire is the 3 00:00:10,720 --> 00:00:14,800 Speaker 1: result of a chemical combustion reaction, typically between oxygen and 4 00:00:14,960 --> 00:00:18,079 Speaker 1: some sort of fuel like wood or gasoline. For the 5 00:00:18,120 --> 00:00:21,920 Speaker 1: reaction to occur, the fuel has to reach its ignition temperature. 6 00:00:22,239 --> 00:00:25,680 Speaker 1: For wood, that's about five hundred degrees fahrenheit or two 7 00:00:25,800 --> 00:00:29,600 Speaker 1: hundred and sixty degrees celsius. The heat decomposes some of 8 00:00:29,640 --> 00:00:33,879 Speaker 1: the woods cellulose, and the decomposed stuff is released as 9 00:00:34,000 --> 00:00:38,680 Speaker 1: volatile gases, like a compound of hydrogen, carbon, and oxygen. 10 00:00:39,000 --> 00:00:41,960 Speaker 1: When the gas is hot enough, its molecules break apart. 11 00:00:42,240 --> 00:00:46,680 Speaker 1: The atoms recombine with the oxygen to form water, carbon dioxide, 12 00:00:46,720 --> 00:00:49,920 Speaker 1: and other products. The heat keeps the fuel at the 13 00:00:49,920 --> 00:00:53,239 Speaker 1: ignition temperature, so it keeps burning as long as there 14 00:00:53,320 --> 00:00:56,480 Speaker 1: is fuel and oxygen. So there you have it. Fire, 15 00:00:56,720 --> 00:01:00,360 Speaker 1: the result of extreme heat, oxygen, and fuel. But what 16 00:01:00,480 --> 00:01:05,119 Speaker 1: about fire extinguishers? They remove at least one of these 17 00:01:05,200 --> 00:01:09,840 Speaker 1: elements from the equation. Fire extinguishers are metal cylinders filled 18 00:01:09,840 --> 00:01:13,120 Speaker 1: with water or smothering material, and when you depress a 19 00:01:13,240 --> 00:01:16,600 Speaker 1: lever at the top, the material is expelled by high pressure, 20 00:01:16,720 --> 00:01:20,240 Speaker 1: kind of like an aerosol. Can imagine a fire extinguisher 21 00:01:20,440 --> 00:01:24,880 Speaker 1: cut in half. Okay, that plastic siphon tube leads from 22 00:01:24,920 --> 00:01:28,280 Speaker 1: the bottom of the fire suppressant reservoir to the top 23 00:01:28,360 --> 00:01:32,320 Speaker 1: of the extinguisher. A spring mounted valve blocks the passageway 24 00:01:32,400 --> 00:01:35,119 Speaker 1: from the siphon to the nozzle, and at the top 25 00:01:35,160 --> 00:01:38,319 Speaker 1: of the cylinder there is a smaller cylinder filled with 26 00:01:38,400 --> 00:01:43,199 Speaker 1: compressed gas liquid carbon dioxide. For example, A release valve 27 00:01:43,319 --> 00:01:46,960 Speaker 1: keeps the compressed gas from escaping. When you pull out 28 00:01:46,959 --> 00:01:50,080 Speaker 1: the safety pin and depress the operating lever, it pushes 29 00:01:50,200 --> 00:01:53,480 Speaker 1: on an actuating rod. The rod presses the spring mounted 30 00:01:53,560 --> 00:01:56,360 Speaker 1: valve down to open up the passage to the nozzle. 31 00:01:56,680 --> 00:01:59,600 Speaker 1: The bottom of the actuating rod has a sharp point 32 00:01:59,640 --> 00:02:04,160 Speaker 1: which pierces the gas cylinder release valve. The compressed gas escapes, 33 00:02:04,440 --> 00:02:08,760 Speaker 1: applying downward pressure on the fire suppressant material. This drives 34 00:02:08,760 --> 00:02:11,520 Speaker 1: the material up the siphon and out the nozzle. The 35 00:02:11,600 --> 00:02:14,080 Speaker 1: proper way to use the extinguisher is to aim it 36 00:02:14,200 --> 00:02:17,640 Speaker 1: directly at the fuel, not the flames, and spray in 37 00:02:17,680 --> 00:02:22,000 Speaker 1: a sweeping motion. There are three main types of extinguisher. 38 00:02:22,320 --> 00:02:25,800 Speaker 1: A water extinguisher can put out things like burning wood, paper, 39 00:02:26,080 --> 00:02:29,880 Speaker 1: or cardboard, but it doesn't work well on electrical fires 40 00:02:30,000 --> 00:02:34,960 Speaker 1: or fires involving inflammable liquids. In an electrical fire, water 41 00:02:35,280 --> 00:02:39,600 Speaker 1: may conduct the current, which could electrocute you. Water will 42 00:02:39,680 --> 00:02:43,880 Speaker 1: only spread an inflammable liquid, making the fire worse. Then 43 00:02:44,280 --> 00:02:47,880 Speaker 1: there's the carbon dioxide extinguisher. The CO two is kept 44 00:02:47,919 --> 00:02:51,560 Speaker 1: in a pressurized liquid form. When the container is opened, 45 00:02:51,760 --> 00:02:55,240 Speaker 1: the CO two forms a gas. This gas is heavier 46 00:02:55,280 --> 00:02:58,720 Speaker 1: than oxygen, so it deplaces the oxygen surrounding the fuel. 47 00:02:59,080 --> 00:03:03,320 Speaker 1: This extinguisher is common in restaurants because it won't contaminate 48 00:03:03,400 --> 00:03:08,240 Speaker 1: cooking equipment or food. The most popular extinguisher material is 49 00:03:08,240 --> 00:03:13,240 Speaker 1: the dry chemical extinguisher. These cylinders contain foam or powder, 50 00:03:13,480 --> 00:03:18,160 Speaker 1: typically made of sodium bi carbonate also known as baking soda, 51 00:03:18,520 --> 00:03:24,360 Speaker 1: potassium bicarbonate, or mono ammonium phosphate. Baking soda starts to 52 00:03:24,440 --> 00:03:28,359 Speaker 1: decompose at only a hundred and fifty eight degrees fahrenheit 53 00:03:28,520 --> 00:03:32,880 Speaker 1: or seventy degrees celsius, and when it decomposes, it releases 54 00:03:33,080 --> 00:03:35,800 Speaker 1: c O two. The c O two, along with the 55 00:03:35,840 --> 00:03:39,920 Speaker 1: insulation of the foam, smothers fire. The best way to 56 00:03:39,960 --> 00:03:43,200 Speaker 1: tell which fire extinguisher you have and which fires it's 57 00:03:43,240 --> 00:03:45,920 Speaker 1: best suited to fight is to look at the rating. 58 00:03:46,400 --> 00:03:49,800 Speaker 1: All fire extinguishers have an A, B or C rating. 59 00:03:50,120 --> 00:03:55,360 Speaker 1: A Class A fire extinguisher works best against fires involving paper, wood, plastic, 60 00:03:55,400 --> 00:03:58,680 Speaker 1: and textiles. A Class B fire extinguisher can put out 61 00:03:58,720 --> 00:04:03,160 Speaker 1: flammable liquid fires you know, things like cooking oil, gasoline, paint, 62 00:04:03,320 --> 00:04:07,040 Speaker 1: or oil, and a Class CE extinguisher is your go 63 00:04:07,200 --> 00:04:11,440 Speaker 1: to for live electrical fires. Each extinguisher will have a 64 00:04:11,600 --> 00:04:14,560 Speaker 1: number by the letter indicating the size of the fire 65 00:04:14,600 --> 00:04:18,559 Speaker 1: that it can tackle, But please be careful. Most fire 66 00:04:18,560 --> 00:04:22,400 Speaker 1: extinguishers contain a small amount of suppressing. You can use 67 00:04:22,440 --> 00:04:25,760 Speaker 1: it up in seconds. That's why they're only effective on 68 00:04:25,880 --> 00:04:29,520 Speaker 1: relatively small fires. To put out a bigger fire, you 69 00:04:29,560 --> 00:04:32,920 Speaker 1: need more equipment like a fire engine, as well as 70 00:04:32,960 --> 00:04:35,880 Speaker 1: trained professionals. But for the blazes that can pop up 71 00:04:35,920 --> 00:04:39,280 Speaker 1: in your house, a fire extinguisher can be a lifesaver. 72 00:04:45,279 --> 00:04:47,520 Speaker 1: Check out the brainstuff channel on YouTube, and for more 73 00:04:47,560 --> 00:04:50,119 Speaker 1: on this and thousands of other topics, visit how stuff 74 00:04:50,120 --> 00:05:04,360 Speaker 1: works dot com.