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Last Update:

16 August 2006

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City of Tucson

PORTABLE FIRE EXTINGUISHERS

are for fighting SMALL fires!

A portable fire extinguisher can save lives and property by putting out a small fire or suppressing it until the fire department arrives. Portable extinguishers, however, have limitations. They are not designed to fight large fires or fires that are spreading quickly. Most portable fire extinguishers sold for homes have a short range of 6 – 10 feet and discharge completely in a very short time of 8 – 10 seconds. They are appropriate for fighting fires such as a stove top or oven fire, or a fire in a wastebasket – if the fire is caught in its early stages. Portable extinguishers will do little against large or established fires.

As a general rule, fire fighting should be left to professionals, and the National Fire Protection Association (NFPA) recommends that the fire department be called in the event of any fire. The NFPA does not recommend teaching children to use fire extinguishers.

In the City of Tucson it is the law that the fire department be notified of all fires.

When to fight a Fire: Personal safety of others is the most important factor when deciding whether to fight a small fire. Before you begin to fight a fire be sure of the following:

  • Everyone has left, or is leaving, the building. Your household should have an evacuation plan and everyone in your home must know what to do in the event of fire.
  • The fire department has been called or is being called. Even if you succeed in putting out the fire, a trained professional should inspect it. In the City of Tucson it is the law that the fire department be notified of all fires.
  • The fire is confined to a small area, such as in a wastebasket, and it is not spreading (getting bigger). A portable fire extinguisher is no match for a large or rapidly advancing fire.
  • Your back is to an unobstructed exit to which the fire will not spread. You must always assume that you may not be able to extinguish the fire you are fighting. If the fire doesn't diminish with your first attack or if anything goes wrong, leave immediately and do not return.
  • The room is not filled with smoke. Fire fighters wear protective breathing equipment because of the dangers of smoke inhalation. Without protection, you may quickly find yourself unable to breathe or see. Smoke can also obscure your exit path.

It is dangerous to fight a fire in any circumstances. If in doubt, leave immediately, close off the area to slow the spread of the fire and smoke, and wait outside for the fire department to arrive.

There are many ways to put out a small fire. Portable extinguishers are a good idea only under certain conditions:

  • The extinguisher must be rated for the type of fire you are fighting: They are designed to fight specific classes of fires. What type of extinguisher to use depends on what is burning.
  • The extinguisher must be large enough to put out the fire. Fire comes in various sizes; generally, larger models can handle larger fires.
  • The extinguisher must be within easy reach. Never move through a fire to get to your fire extinguisher.
  • The extinguisher must be fully charged.
  • The operator must know how to use the extinguisher. When something is on fire, there is no time to find the instruction book or to study the instructions printed on the extinguisher's label. You should be familiar with the operation of each type of portable fire extinguisher in your home.
  • The operator must be strong enough to lift and operate the extinguisher. Most home fire extinguishers are small and lightweight.

Types of Fire Extinguishers: It is essential that the type of extinguisher you use is appropriate for the type of fire you are fighting. If, for example, you spray water on a grease fire, the water will cause the grease to splatter and the fire may spread. Similarly, lf you dowse live electrical equipment with water, you are putting yourself in danger of electrical shock. There are many types of portable fire extinguishers on the market. Depending on their intended use, fire extinguishers use a variety of "fire extinguishing agents"– the water or the chemicals(s) that put out the fire.

Independent testing laboratories test and rate portable fire extinguishers to determine the type and size of fire each model can put out. Do not buy a portable fire extinguisher if it does not carry the label of an independent testing lab.

  • Dry Chemical extinguishers are usually rated for multiple purpose use. They contain an extinguishing agent and use a compressed, non-flammable gas as a propellant.
  • Halon extinguishers contain a gas that interrupts the chemical reaction that takes place when fuels burn. These types of extinguishers are often used to protect valuable electrical equipment since they leave no residue to clean up. Halon extinguishers have a limited range, usually 4 to 6 feet. The application of Halon should be made at the base of the fire, even after the flames have been extinguished.
  • Water extinguishers contain water and compressed gas and should only be used on Class A (ordinary combustibles) fires.
  • Carbon Dioxide (CO2) extinguishers are most effective on Class B and C (liquids and electrical) fires. Since the gas disperses quickly, these extinguishers are only effective from 3 to 8 feet. The carbon dioxide is stored as a compressed liquid in the extinguisher; as it expands, it cools the surrounding air. The cooling will often cause ice to form around the "horn" where the gas is expelled from the extinguisher. Since the fire could re-ignite, continue to apply the agent even after the fire appears to be out.

Types of fires: The A, B, C, D, K classifications describe a fire's fuel – i.e. what's burning. When the classifications are used for rating fire extinguishers, they tell you what classes of fire the unit should or should not be used on.

 

  • Class A Extinguishers will put out fires in ordinary combustibles, such as wood and paper. The numerical rating for this class of fire extinguisher refers to the amount of water the fire extinguisher holds and the amount of fire it will extinguish.
  • Class B Extinguishers should be used on fires involving flammable liquids, such as grease, gasoline, oil, etc. The numerical rating for this class of fire extinguisher states the approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish.
  • Class C Extinguishers are suitable for use on electrically energized fires. This class of fire extinguishers does not have a numerical rating. The presence of the letter "C" indicates that the extinguishing agent is non-conductive.
  • Class D Extinguishers are designed for use on flammable metals and are often specific for the type of metal in question. There is no picture designator for Class D extinguishers. These extinguishers generally have no rating nor are they given a multi-purpose rating for use on other types of fires.
  • Class K Extinguishers are the newest classification providing for protection of cooking appliances that use combustible cooking media (vegetable or animal oils and fats). These extinguishers do not carry a numerical rating.

Note: Extinguishers provided for the protection of cooking grease fires shall only be of the sodium bicarbonate or potassium bicarbonate dry chemical type (Class B-C). Cooking grease fires are a special hazard requiring agents suitable for this application. Sodium bicarbonate and potassium bicarbonate dry chemicals are considered suitable for the special nature of heated grease fires, others may not be due to agent characteristics. Additionally, the residues of multipurpose dry chemical extinguishers (Class A-B-C) can cause corrosion when left in contact with metal surfaces. NFPA 10 and 96 standards.

Multi-Class Ratings

This is the new style of labeling that shows this extinguisher may be used on Ordinary Combustibles, Flammable Liquids, or Electrical Equipment fires.
Many extinguishers available today can be used on different types of fires and will be labeled with more than one designator, e.g. A-B, B-C, or A-B-C. Make sure that if you have a multi-purpose extinguisher it is properly labeled.

This is the old style of labeling indicating suitability for use on Class A, B, and C fires.
This is the new labeling style with a diagonal red line drawn through the picture to indicate what type of fire this extinguisher is NOT suitable for. In this example, the fire extinguisher could be used on Ordinary Combustibles and Flammable Liquids fires, but not for Electrical Equipment fires.

Household Extinguishers:  Most household portable fire extinguishers on the market use a "dry-chemical" extinguishing agent. Depending on the type of dry-chemical extinguishing agent used, these will be label BC (meaning they are rated for fighting Class B and C fires) or "multipurpose" ABC (rated for fighting all three classes of fires).

Extinguisher Size:  A–rated and B–rated portable fire extinguishers are rated for the size of fire they can extinguish.  When selecting a fire extinguisher, the rule of thumb, of course, is the bigger the better. Larger extinguishers, however, can be heavy and therefore difficult to operate.

It is important for safety reasons that you have some idea of a portable extinguisher's capacity before you attempt to fight a fire. Many people are unaware that the majority of portable extinguishers are best suited for fighting very small fires (in wastebasket or toaster oven, for example). Some discharge completely in as few as 8 seconds.

The "size" of an extinguisher is determined by standard tests during which experienced laboratory technicians attempt to put out fires in a controlled setting. All extinguishers rated for Class A or B fires are labeled with a number: from 1 to 40 for an A rating, and from 1 to 640 for a B rating. This number is a relative indication of the extinguisher's "size" or fire-fighting effectiveness. The larger the number, the larger the fire that extinguisher can put out. Most extinguishers sold for uses in the home have 1-A, 2-A, or 3-A ratings for Class A fires and 5-B, 10-B, 20-B, or 40-B ratings for B fires.

A typical rating for an ABC household model might be "2-A: 10-B: C." A typical rating for a BC extinguisher might be "10-BC." There is no number to indicate size attached to the C rating. The C rating is included to tell you only that the extinguisher can be used on fires involving energized electrical equipment. Such a fire will always involve either Class A combustible or Class B Flammables, hence the multi-rating combinations.

Parts of Portable Fire Extinguisher: Most portable extinguisher for home use consists of six basic parts.

  • The cylinder: The body of the stored pressure extinguisher holds some combination of extinguishing agent and expellant gas.
  • The handle: The handle is nothing more than a grip for carrying and for holding the extinguisher when you use it. Handle design will vary widely depending on an extinguisher's make and model, but all portable extinguishers weighing more then 3 pounds are required to have handles. (Note: Lifting an extinguisher by the handle will not discharge the unit.)
  • The trigger: This is usually a short lever mounted above the handle at the top of the extinguisher, although some models may differ. Squeezing the trigger releases the extinguishing agent through the nozzle.
  • The nozzle or horn: Depending on the type and model, the extinguishing agent is expelled from the top of the extinguisher through a fixed nozzle, or a nozzle or cone attaches to the extinguisher by a short hose.
  • The pressure gauge or pressure indicator: Over time, the pressure stored in a portable fire extinguisher may dissipate. An extinguisher that has lost too much pressure will not operate properly. Therefore, stored-pressure extinguishers are designed with a built-in pressure gauge or pressure indicator so you can check the extinguisher's operating pressure. (A pressure check should be done at least once a month.)
  • The locking mechanism: To prevent accidental discharge, all portable extinguishers come with some sort of locking mechanism that must be removed or released before the extinguisher will work. In most modern home fire extinguishers, there is a pin, with a large loop at one end, located below the trigger. You must pull the pin out before you can squeeze the trigger to discharge the extinguisher. See the following illustration.

How to Operate a Portable Fire Extinguisher: There are four basic steps to operating a portable fire extinguisher. An easy way to remember the procedure is to think of the word "PASS."

  • Pull the Pin: Holding the extinguisher with the nozzle pointing away from you, release the locking mechanism. In most cases, this means pulling out the pin located below the trigger.
  • Aim low: Standing 6 to 8 feet away from the fire, point the extinguisher nozzle at the base of the fire – the lowest point of the fire nearest you. Extinguishers are designed to be operated in an upright position. Always hold the extinguisher vertically. Never cradle it horizontally or at an angle in your arms.
  • Squeeze the trigger: Squeeze the trigger slowly and evenly. This will release the extinguishing agent and expel it through the nozzle.
  • Sweep side to side: As the extinguishing agent is expelled, sweep the nozzle from side to side – "driving the fire back.." As the fire closest to you goes out, you may move closer to the fire and continue the sweeping motion until the fire is extinguished. Remember, hold the extinguisher upright. If the fire does not diminish immediately, get out of the building!

Extinguishing Common Household Fires: Even a small fire should be treated with respect, and you should never attempt to fight a fire unless it is safe to do so. Before fighting a fire, be sure the fire department has been called or is being called and be sure you have an unobstructed exit route. If the fire you are fighting begins to spread or the room fills with smoke, leave the area immediately. Remember: big fires start small, and portable fire extinguishers have their limitations. In the City of Tucson it is the law that the fire department be notified of all fires.

  • A grease fire in a frying pan: The safest and easiest way to extinguish a frying-pan fire is to smother it by sliding a tight-fitting lid over the pan, and then turning off the burner. This will cut off the fire's supply of oxygen. Do not remove the lid or attempt to move the pan until the pan has cooled completely. Never attempt to carry the pan to a sink or outdoors. If you use a dry-chemical extinguisher remember to stay back at least 6 feet to avoid splashing burning grease out of the pan. Never use water on this type of fire
  • A grease fire in an oven or broiler: Turn off your oven or broiler. Because kitchen ranges are vented, simply keeping the oven door or broiler drawer shut will usually contain, but probably not smother, the fire.  However, opening the door or drawer will invariably cause the fire to flare up. When opening your oven door or drawer do it slowly and with extreme care. Have a BC or ABC rated extinguisher ready. Do not attempt to move the pan or baking dish until the fire is out and the pan or dish has cooled completely.
  • A wastebasket fire: A fire in a wastebasket usually involves burning paper. Staying back from flames as far as possible, apply water to the fire until it is out. Or use a portable fire extinguisher rated for Class A fires. You may also safely use a dry-chemical extinguisher that is rated only for Class B and C fires; however, because a BC extinguisher has no A rating it may not be fully effective.
  • Fires involving furniture, drapes, or tablecloths: These are Class A fires and can be extinguished with water.  Unlike wastebasket fires, fires involving furniture, drapes, or tablecloths are not "contained" and can spread rapidly. For this reason it is often best to fight them with a portable fire extinguisher rather than buckets of water. Once the burning fabric is extinguished and completely cooled it should be removed from the house; the potential for rekindling, especially with furniture, is very high. Be sure to protect yourself from burns when removing the item.
  • A car fire: If a car fire involves only upholstery (for example, a fire in the back seat started by a cigarette), use any fire extinguisher available. If the fire involves the engine or dashboard, however, the fire could quickly become very dangerous. Always shut off your engine. Such car fires can be fought with a fire extinguisher with a B:C or ABC rating. Do not open your hood; aim your extinguisher through the car's grill. If you cannot extinguish the fire immediately, leave the area, keep everyone far way from the car, and wait for the fire department.
  • A fire involving gas lines: The only safe way to fight a fire in a kitchen range, furnace, or space heater involving natural gas or propane is to shut off the supply of gas. Know where gas-line shutoff valves are in your home. The same is true for any fire involving heating oil under pressure (such as in a furnace burner).  Never attempt to extinguish a gas fire without shutting off the fuel supply. An open gas line is a potential explosion hazard.

Remember: Even if a fire appears to be out, it can re-ignite. After using your portable fire extinguisher, watch the fire area until it is inspected by the fire department.

In the City of Tucson it is the law that the fire department be notified of all fires!