The Trainer’s Corner: The fire extinguisher, an overlooked tool
The objective of this month’s column is to help fire fighters become familiar with perhaps one of the most overlooked tools carried on their fire apparatus, the portable fire extinguisher. Granted, they are somewhat limited, being designed specifically to fight small (incipient) developing fires, but I challenge you to reconsider the use of these units in a “quick” knockdown situation.
Proper instruction on the use of fire extinguishers can improve the effectiveness of a fire department and reduce the costly effects of fire loss. Fire extinguishers come in a variety of types and sizes and fire fighters should know the particular extinguishers carried on their apparatus. Considering the fact that the public looks to you the fire fighter as an “expert,” it would be good for you to know your stuff.
There are five classes of fire, four traditional and one fairly new one, the “K” class. The type or nature of the material burning (fuel) defines the fire.
Class A fires involve ordinary combustibles like wood, paper, plastics, cloth and rubber. Water is the basic fire-extinguishing agent for Class A materials. The freezing problem with loaded stream extinguishers is dealt with by adding an alkali salt as an anti-freezing agent.
Class B fires involve flammable and combustible liquids, gases and greases. Water-based foam extinguishers, used on Class B fires, have either AFFF (aqueous film-forming foam) or FFFP (film-forming fluoroprotein foam) of both the regular and polar solvent types. CO2 (carbon dioxide) extinguishers are effective in smothering Class B or C fires.
Class C fires involve energized electrical equipment. Dry chemical extinguishing agents are particles that are propelled by a gaseous medium. There are three general categories of dry chemical extinguishers: sodium bicarbonate-based, potassium-based, and multi-purpose dry chemicals. Sodium bicarbonate-based and potassium-based (regular dry chemical extinguishers) are effective on both Class B and C fires.
Multipurpose dry-chemical extinguishers are effective on Class A, B and C fires. These dry chemicals are very effective due to their coating action, which reduces the chance of re-ignition. They are, however, unfriendly when protecting certain sensitive items.
Halons or halogenated hydrocarbons have been banned by an international treaty for destroying the Earth’s ozone layer. They have been replaced by non-volatile gases (clean agents) that do not conduct electricity or leave a residue.
Class D fires involve combustible metals and alloys like magnesium, sodium and potassium. Cartridge-operated extinguishers are used for some regular and multi-purpose dry chemical and most dry powder Class D extinguishers.
Class K is a fairly new classification of fire (1998), involving fires in combustible cooking fuels such as vegetable or animal oils and fats. Its fuels are similar to Class B fuels, but involve higher temperature cooking oils, which have special characteristics.
Wet-chemical extinguishers are used for special applications, such as Class K fires. They are water-based solutions of a potassium carbonate-based chemical, a potassium acetate-based chemical, a potassium citrate-based chemical, or a combination of these.
It is important to use the right type of fire extinguisher. Using the wrong extinguisher can be worse than not using one at all! It is also important to consider the amount of fuel on fire. The wrong size extinguisher may not completely extinguish the fire.
It should be understood that fire extinguishers have limited capabilities and trying to exceed these capabilities can increase the damage done and may result in injury.
Care and maintenance of fire extinguishers is fairly simple. The inspection of fire extinguishers by fire fighters is usually a visual inspection. Dry chemical or powder extinguishers should be occasionally turned upside down and shaken or hit with a rubber mallet to keep powders from packing at the bottom.
Some popular fire extinguishers have been declared obsolete and should be removed from service. Most of these extinguishers have the potential to explode when pressure is applied during use. These include: soda acid, chemical foam (except film-forming), vaporizing liquids, cartridge-operated water or loaded-stream types, and copper or brass extinguishers with solder or rivets (except pump tanks).
Extinguishers in public buildings should be checked every 30 days, and ones on apparatus should be inspected each time the vehicle undergoes inspection. Each unit should have a tag indicating its last service or inspection date.
The pin seal should be firmly in place. If the unit has a gauge, it should register the proper pressure. Carbon dioxide extinguishers do not have gauges and therefore can only be checked by weighing them. The filled weight is stamped on the cylinder. A last check should be to see if the unit is within the proper time frame for testing. Multi-purpose dry chemical extinguishers are tested every six years, rotating between a six-year test (shooting off the powder to make sure everything is in working order) in year 6 and hydrostatic testing (testing the cylinder’s ability to hold pressure) in year 12. Pressurized water extinguishers and carbon dioxide extinguishers get hydrostatic tested every five years.
Use the acronym “PASS” to remember the four simple steps for operating most fire extinguishers: Pull the pin. Aim the nozzle. Squeeze the handle. Sweep the base of the fire. Before pulling the pin, be sure that you have selected the appropriate extinguisher based on the size and type of fire. Check to see if the unit has a full charge.
Step one is pulling the pin that prevents the handle from being accidentally squeezed. Point the nozzle in a safe direction and discharge a short test burst to ensure proper operation. Carry the extinguisher to within stream reach of the fire. Some extinguishers can reach 50 feet, but reach and effectiveness are two different matters. The practical effective range of a pressurized water or foam unit is about 20 feet; dry chemical units are about 15-20 feet and CO2 types from 10-15 feet. (Caution: the nozzles of CO2 may freeze during discharge, so touching the nozzle or horn with bare skin may result in frostbite.)
Aim the extinguisher towards the base of the fire closest to you. Always keep an escape route open. Do not allow the fire to come between you and the exit. The object of aiming at the base of the fire is to sweep it away from you, confining it to where it is and driving it back to its origin. Aiming at other points may cause the fire to spread beyond the capability of the extinguisher. Aim the extinguisher from the proper distance, set by the room and fire size.
Squeeze the handle. Continue to squeeze the handle long enough to cover the fire. Short blasts are okay, but too many only empties the unit without extinguishing the fire.
Sweep the area of the fire by keeping the nozzle aimed at the base of the fire, continuing to push the fire back away from you.
Watch for smouldering hot spots or possible re-ignition of flammable liquids. Make sure the fire is out. Always back away from the fire area. Do not turn your back on the fire. Flag the extinguisher after use so that no one will try to use it again until it is recharged.
The drill: You will need to make or acquire a solid metal pan no more than three feet square. Our pan is made of heavy sheet metal seamed at the corners with five-inch sides. Scrap wood, paper or a variety of combustible liquids can be used as fuels. We prefer diesel fuel, but kerosene would work as well. Do not use gasoline You will need a suitable torch or other device to safely light the fire pan. You can rent extinguishers for your drill night if there are not enough on the apparatus. Lastly, arrange to have the expended (flagged) units re-charged as soon as possible after the drill.
Safety precautions during this live
fire drill should include the following: determine a safe location (outdoors) to conduct the drill. The person igniting and/or fuelling the fire should be wearing full PPE. The fire fighter doing the drill should be wearing full PPE. The burn pan should be placed in a location where spilled fuel cannot run away. Do not pour combustible liquids into a hot pan. For more safety requirements, check NFPA 1406. Always have a back-up extinguisher crew at the ready.
Have fire fighters don their PPE. In an appropriate place outdoors, have Class A and B fires in pans. Fire fighters should take turns putting out Class A and Class B fires using PASS.
- Fire fighter properly dons PPE.
- Selects the appropriate extinguisher based on the size and type of fire.
- Checks to see if the unit has a full charge.
- Carries and handles the extinguisher properly to a safe stream reach.
- Does test burst before attacking the fire.
- Stays upwind of the fire.
- Maintains proper distance from the fire.
- Sweeps agent over entire fire.
- Ensures that the fire is extinguished.
- Does not turn their back to the fire.
- Flags extinguisher after use.
References: NFPA 1001:3-3.15, 4-5.1, NFPA 10, NFPA 1406, IFSTA Essentials of Firefighting (IV Edition), Firefighter’s Handbook, Essentials of Firefighting and Emergency Response, Kost Fire Safety (Kelowna).
Ed Brouwer is the Fire Chief/Training Officer for Canwest Fire. The 17-year veteran of the fire service is also a Fire Warden with Ministry of Forests, First Responder III instructor/evaluator for FNESS (First Nations Emergency Services Society), Local Assistant to the Fire Commissioner as well as a fire service motivational speaker and chaplain. E-mail firstname.lastname@example.org.
December 17, 2007 By Ed Brouwer
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