Fire! Which Extinguisher Should You Use?

HOW often we walk right past that silent little sentinel on the wall without ever sparing it a thought! Yet, one day it might save our office or factory or even our home from going up in smoke. Portable fire extinguishers can help prevent a small problem—a pan aflame on the stove or curtains ignited by a heater—from getting out of hand. Like rapid-response weapons, they are designed to snuff out a cruel enemy before it gathers strength.

Because this enemy comes in many forms—wood fires, oil and gas fires, electrical fires—portable extinguishers also come in many forms. Naturally, you want to know both your enemy and your weapons. This does not mean having the insight of a professional fire fighter, but it does mean knowing a few basic principles. For example, what would you have done in the following situation?

A pastry cook was heating a rack of 20 new, well-oiled pans in an oven when preparing to bake bread. The thermostat was faulty, however, and the temperature soared, making the oil smoke. The cook, with gloved hands, quickly opened the oven and pulled the rack out. But in doing so, he immersed the smoking oil in a rich bath of air. Whoof! Spontaneous combustion sent flames shooting toward the ceiling. Unharmed, the cook dashed off and returned within seconds armed with a carbon dioxide fire extinguisher and quickly put the fire out. But immediately more smoke formed, and the oil ignited again. This cycle was repeated four times! Fearing the extinguisher would soon be exhausted, the cook pulled a fire blanket from its nearby holder and tossed it over the rack. To his relief, it snuffed out the fire—and kept it out.

Naturally, we want to use the best weapons at hand to extinguish a small but threatening fire. But had the cook known about spontaneous combustion—a strong possibility whenever there is smoke—he might simply have turned the oven off, kept the doors shut, and let  the contents of the oven cool down naturally. Or he might have employed the fire blanket first and then, if necessary, the carbon dioxide extinguisher. Whatever the case, the experience shows the value of a basic knowledge of fires and how best to put them out.

The “Triangle” That Spells Fire

What is called the fire triangle is a common-sense formula that sets out the conditions for combustion: fuel plus oxygen plus heat equals fire. Remove just one component, and you not only put out the fire but also prevent further fire. Let’s see how this works.

FUEL: Like us, fires die without food. Firemen exploit this principle in forest and brush fires when they create a firebreak in the path of the main fire. In a kitchen setting, eliminating the fuel may simply mean turning off the gas. In other settings, however, eliminating the fuel may be difficult if not impossible.

OXYGEN: Once again, like us, a fire must breathe. Toss a shovelful of dirt or a fire blanket over a fire, and you smother it. The oxygen level, incidentally, need not go down to zero for a fire to suffocate. If you reduce the oxygen level from the normal 21 percent in the air around us to 15 percent, many substances—flammable liquids, for example, and even some solids—will no longer burn.

HEAT: The heat source to start a fire could be a space heater, a stove, wires to an overloaded electrical outlet, a spark or cinder, lightning, or the heat generated by decaying vegetation, volatile chemicals, or any number of other things. Remember, if you see smoke, especially if it is rising from fats or cooking oils over a heat source, spontaneous combustion could be just seconds away.

Tailor-Made for Every Kind of Small Fire

While many homes do not have fire extinguishers, factories, offices, and public buildings are often required by law to be equipped with them. The basic types are water, wet chemical, foam, dry powder, and carbon dioxide. Halon extinguishers are being phased out because it is thought that they are destructive to the ozone layer in the earth’s atmosphere. To help users choose the correct extinguisher in an emergency, most models have picture symbols showing where they can and cannot be used, or they may be color coded. And most have a letter, such as A, B, or C, showing a specific fire classification. The propellant, pressurized gas, forces the active ingredient out through the nozzle at high velocity when the trigger handle is squeezed. Because extinguishers contain gas under pressure, they need to be tested from time to time. And extinguishers should always be mounted near exits and should be easy to access.  Let’s now take a brief look at each type of extinguisher.

Dry powder extinguishers chemically inhibit combustion and come close to being the universal fire retardant. Not only is dry powder effective against both class A and class B fires but it is also useful in combating class C (electrical equipment) fires. Understandably, this multipurpose extinguisher offers excellent protection for your home. Dry powder tends to make a mess—but then a mess might be a small price to pay!

Pressurized water extinguishers are ideal for fires involving paper, wood, plastics, rubbish, or fabrics. These are often called class A fires. Water’s potency as an extinguishing agent stems from its great capacity for absorbing heat. In sufficient volume, water simply steals heat faster than the fire can regenerate it, and thus the fire dies out. But do not use water on flammable liquids. You merely spread the fire—explosively! Also, because water conducts electricity, you should not use it or any extinguisher that incorporates it where there may be live electrical wires.

Wet chemical extinguishers employ a pressurized solution of alkali salts in water and are particularly effective against fats and cooking oils but not against petroleum products. They are also effective against class A fires.

Foam extinguishers work well, not only on class A fires but especially on fires involving flammable liquids (industrial lubricants, fuels, paints), generally known as class B fires. There are two kinds of foam extinguishers, so check which one best suits your needs. When applied to a burning liquid, the foam coats it with an impervious film that arrests flammable vapors and also keeps oxygen away. Thus, foam must be applied more gently so that it does not penetrate the liquid but, rather, spreads readily over it. Be careful not to use foam near electricity.

Carbon dioxide extinguishers can be used against practically all fires except gas fires. They work on the principle that carbon dioxide displaces oxygen. But as we saw earlier, if the combustible keeps its heat, spontaneous reignition is possible. Carbon dioxide is a gas, so a breezy, open environment limits its effectiveness. Its cleanness, however, makes it the extinguisher of choice for use on delicate machinery and electronic equipment. In confined spaces, though, carbon dioxide can asphyxiate, so if you use it in such a setting, be sure to leave when the fire is out and shut the door behind you.

The fire blanket * is a handy fire fighter and is  ideal for small, contained fires such as you might have on the top of a kitchen stove or in a small patch of carpet. Just pull the blanket from its tidy little wall-mounted holder, stretch it out in front of you to protect yourself from the flames, and place the blanket over the fire. Of course, if you have not already done so, turn the heat source off immediately if at all possible.

Fire blankets are also lifesavers should your clothing catch fire. In that event, remember this vital rule: “Stop, drop, and roll.” Never run; you simply fan the flames. If you or anyone else is able to wrap a fire blanket around you as you roll, you will snuff the fire out even more quickly.

Better Than Extinguishers

The best protection against fires is, of course, fire prevention; so use good sense. Keep matches and lighters away from children. Remove all materials on or near your stove that could catch fire. Never cook while wearing clothes with loose, dangling sleeves that may catch fire. Install smoke detectors in your home.

Here are some additional tips. Never overload electrical outlets or extension cords. Never leave fats or oils frying unattended on a hot stove. Be careful where you place space heaters. If you have bottled gas cylinders near the house, point the safety valves—a potential blowtorch in a fire—away from the building. Use electrical fuses of the correct size. Replace damaged electrical cords.

Have you considered home fire drills? These can indeed save lives. Arrange for the family to meet at a specific location—any clearly defined safe spot that is easy to find day or night. And delegate responsibilities: Who will help infants or disabled individuals to safety? Who will call the fire department? Yes, drills save lives because they rehearse the right response, making it automatic and speedy.

Should the Worst Happen

Remember, goods can be replaced but lives cannot. Do not risk your life to fight a fire. If, however, it is safe for you to go ahead and fight the fire, do so from a position that will allow you access to an exit. But if you doubt that the extinguisher you have is the correct one or if you fear that the fire is too big for it, get out fast and call the fire department.

Note, too, that smoke, especially toxic smoke from synthetics, kills more people than flames—it can kill in less than two minutes! So when escaping from a burning building, stay low. There is less smoke near the floor, and the air is cooler. If possible, hold a damp cloth over your mouth. Before using a door, touch it with the back of your hand. If it’s hot, fire is on the other side; find another exit. And shut all doors behind you as you go. This limits the oxygen flow to the fire. Elevators, of course, are an absolute no-no in a fire—they might trap you and become an oven!

So if you intend to purchase fire protection for your home, car, or business, it may be best to discuss the matter with your local fire authorities. More specific details may vary from country to country and so are outside the scope of this article.

In any case, next time you see one of those silent little sentinels, stop and get better acquainted. You may be deeply indebted to it one day.

[Footnote]

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FIRE

fuel

heat

oxygen

[Pictures]

CLASS A

CLASS B

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Chubb Fire Safety

[Diagram on page 26]

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If your clothes catch fire, don’t run

1. STOP

2. DROP

3. ROLL

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© Coastal Training Technologies Corp. Reproduced by Permission

[Picture on page 24]

There are many multipurpose fire extinguishers for the home

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Above illustration: Reprinted with permission from NFPA 10-1998, Portable Fire Extinguishers, Copyright © 1998, National Fire Protection Association, Quincy, Massachusetts 02269. This reprinted material is not the complete and official position of the NFPA on the referenced subject which is represented only by the standard in its entirety.