Puttin’ out the Fire
The last item on the home fire safety equipment list is the fire extinguisher.
You can easily compare the three items as parts of a three-legged stool: all are necessary to reduce the loss of life and property in home fires. Without just one of the three, that stool collapses.
The role of the residential fire extinguisher is similar to a sprinkler system with one variable: you. A small fire can be easily put out if caught in time and attacked with the right equipment and knowledgeable equipment user. Professionals stress that an extinguisher’s primary function is to help people escape safely.
What Suppressant Works with Which Fire
There are three different materials used in fire extinguishers: water, pure carbon dioxide and dry chemical foam, the most popular and most effective for home use. Water works well on Class A fires where the fuel is ordinary combustibles like wood, paper, etc. However, on Class B fires (flammable liquids, including cooking oils and fats), the water mixes with the liquid, dilutes and spreads the fire. The degree to which the burning liquid is diluted is not enough to extinguish the flame. Water on a Class B fire not only does not work, it could make the fire worse. The use of water on Class C, electrical fires, is even more dangerous. Water conducts electricity. The fire extinguisher user is at the end of that conductivity and could get electrocuted.
With pure carbon dioxide extinguishers, the gas is contained in pressurized liquid form in the canister. When the pressure is released and the canister opened, carbon dioxide enters the atmosphere in its gas form. Since it is heavier than oxygen, it smothers the fuel and displaces the oxygen that feeds the flames. This type of extinguisher is often used in restaurants since it does not contaminate the food or cooking equipment.
The chemical in dry chemical foam extinguishers is usually sodium bicarbonate (baking soda). Exposed to temperatures of just 158 degrees F, sodium bicarbonate decomposes, releasing carbon dioxide which, with the foam, smothers the fire.
Residential fire extinguishers are fairly lightweight and easy to use. The trade-off is that they do not contain large quantities of the fire suppressant material. For this reason, your quick, calm reaction to a small flame is very important.
How an Extinguisher Works
Before we explain the basics of using a fire extinguisher, it’s good to understand a little about how the equipment works. Extinguishers work much like aerosol cans. The metal canister contains the water or suppressant material under pressure. At the top of the canister is a lever kept in place with a metal safety pin. When the pin is pulled and the lever depressed, the material is released through the nozzle. The compressed gas is contained in a smaller cylinder near the top of the extinguisher with a release valve that keeps the pressurized gas from escaping. Dry chemical extinguishers generally will have a pressure gauge. If that gauge indicates “recharge,” the pressure may be too low to expel the suppressant. The National Fire Protection Association recommends having dry chemical extinguishers inspected every six years, even if the gauge indicates the correct pressure. To keep track of the age of the equipment, it may be a good idea to identify the purchase date of the extinguisher with an indelible marker.
The best location for an extinguisher is near an exit. More on why in the next section on how to use an extinguisher.
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