FAQ about Fire Extinguishers

Stored-Pressure Extinguishers compact the Dry Chemical.

NO! Stored-pressure fire extinguishers have pressure being exerted from the top. This helps to keep the chemical fluidized during storage and compaction tests (this is also the reason for always pressurizing units through the valve and downtube). The pressurizing gas is present between dry chemical particles and when the valve is opened, the pressurizing gas expands and discharges the chemical. ALL tested extinguishers are subjected to vibration and compaction tests regardless of the design.

Cartridge operated extinguishers are not under constant pressure and as a result they are susceptible to tampering, (fill caps loosened, cartridges loosened, hoses loosened), and the chemical may be compromised with moisture or foreign objects. Cartridge operated extinguishers, by design, are more susceptible to moisture intrusion than stored pressure extinguishers.

Extinguishers with high Ratings will put out larger fires.

Ratings have never put out a fire, fire extinguishers in the hands of capable operators put out fires. Fire tests are run on only one type of fire. The larger the fire, the larger the rating and the longer the extinguisher must discharge. So the rating is a statement of the capability of the extinguisher in very precise conditions.

Stainless Steel Extinguishers can’t corrode.

While stainless steel is LESS SUSCEPTIBLE to corrosion, and is far superior for construction of water and foam extinguishers, that does not take away the possibility of corrosion. Quality of water supplies used to refill water and foam extinguishers varies greatly. The amount of Chlorine and Chlorides in these water supplies will have an effect. As little as 30 Parts Per Million (PPM) of Chlorine will cause stainless steel to corrode. Installing stainless steel extinguishers in salt atmosphere environments may also corrode the outside of the shell over a period of time. It has been our experience that stainless steel extinguishers left OUTSIDE, UNCOVERED IN COASTAL ENVIRONMENTS DO VERY WELL, since rain is allowed to wash off built up salt. If the same extinguisher is put into an UNVENTILATED CABINET OR HAS A COVER IT CORRODES VERY QUICKLY.

Cleaning of Extinguishers.

Cleaning of units is useful on all fronts. It means someone has looked at the unit recently, a clean unit makes any problems that may exist become more evident, it won’t blend in with the background, helps to remove dirt and moisture trapped in the dirt that can lead to corrosion, thus extending the life of the extinguisher. Goto top of page

Alcohol Type foams are applied the same as other foams.

All flammable liquid fires are not alike; neither are all foams. The right foam must be used the right way in order to put out different flammable liquid fires. Foam concentrates, such as the FFFP, are designed for use on alcohol fires (including other polar solvents such as MEK, methanol and glycol) have an additive called a copolymer. When this type of foam makes contact with a polar solvent, a membrane is formed by the copolymer. You can see this membrane on the surface of the fuel. It looks almost like the skim you would see on milk after it has been heated. It is this membrane or skim that puts the fire out and secures the vapors. In order to allow this membrane to form, you can’t disturb the fuel surface when the foam is being applied. This means that you can’t just stand back and “lob” the foam in to the middle of the fuel. Instead, the foam must be gently bounced off an object either in back or in front of the fuel and allowed to gently flow over the surface. The more gentle the application of the foam, the more likely the membrane will form. The foam will seem to just “disappear” when it hits the surface if the membrane isn’t allowed to form. This is happening because the polar solvent is pulling the water out of the bubbles and breaking down the foam.

On more common hydrocarbon fires (such as gasoline, diesel and oil), Alcohol Type Foams work the same way as other foams. No membrane needs to be formed and the foam may be “lobbed” onto the surface. It is still a good idea to “bounce” the foam onto the surface if possible to get a better build up of foam. Disturbing the fuel surface is not so critical if only hydrocarbons are involved. If both hydrocarbons and polar solvents are mixed together (such as “Gasohol”)? If thereis more than 10% polar solvent in the mixture, the fire should be treated as if it were all polar solvent. Goto top of page

Always use the oldest extinguishers for training.

This really isn’t a good idea. Earlier we touched on ratings and different flow rates. Just as different extinguishers have different flow rates and discharge times. People should learn a technique based on extinguishers that they will use, they need the “feel” of the extinguisher when a real fire incident happens. Goto top of page

Two 20B extinguishers don’t equal a 40B requirement.

NO Dry chemical extinguishers have no “securement” capabilities. When using a dry chemical extinguisher on flammable liquids, the operator will either put out all of the fire or none of it. It is impossible to put out half of the fire and go get another dry chemical extinguisher to put out the other half; the fire will reflash over the entire surface area. When the standard calls for a minimum rating of an extinguisher – this is what must be installed. Goto top of page

Dry Chemical “smothers” the fire.

Only in certain circumstances. On Class B fires, dry chemical interrupts the chain reaction. During the early stages in the development of dry chemical agents it was thought that the fire was being smothered. Regular Dry Chemical (sodium bicarbonate) and Purple-K (potassium bicarbonate) break down in a flame front to form carbon dioxide and water vapor. However, there is neither enough carbon dioxide to extinguish the fire, nor is there enough water vapor to extinguish the fire.

On a Class B fire, dry chemical interrupts the chain reaction and extinguishes the fire. This is why it is important to look for a “flash back” when using dry chemical on a liquid fuel fire. There is still oxygen, fuel and hot surfaces present to allow the fire to re-ignite. On Class B fires, Dry chemical does not cool anything down, does not take away the oxygen and does not take away the fuel.

On Class A fires, only ABC or multipurpose dry chemical is effective. ABC dry chemical (monoammonium phosphate) will start to break down at between 350 deg. F and 400 deg. F to form a molten residue that will stick to the burning embers and exclude oxygen. This is the only circumstance that dry chemical may be said to “smother” the fire. It is also important to remember that the ABC dry chemical must be applied to the burning embers in order to have it work. It may be necessary to “break apart” a Class A fire to make sure that all of the burning surfaces are covered. Goto top of page

The requirements of Standards will always be enough.

All Standards are minimum requirements by definition. Are you doing the customer any favors by going with the minimum requirements? Maybe not. How dangerous is the hazard? What is the fire history for that type of operation or industry? What is the customers history of fire incidents? Consider how large any fire is going to be, how many extinguishers and what sizes will be required to extinguish it, what sort of other risks are adjacent to the facility, how long until help will arrive. Goto top of page

Cylinder passes Hydrostatic test has no need of visual inspection.

No! It is possible for a cylinder to pass hydrostatic testing in spite of having disqualifying features, features that have occurred during in-service field use, e.g., cuts. visual inspection. Visual cylinder requalification proceeds hydrostatic testing, it doesn’t replace it. If the visual inspection reveals cylinder features that are severe enough then the cylinder should be condemned and thus a hydrostatic test need not be performed. Cylinders can be visually condemned for any of the following reasons: Dents Cuts, Gouges or Digs; Pitting or General Corrosion; Fire Damage Arc and Torch Burns. Goto top of page

Gauge not exactly the right pressure – unit needs repair.

Tests are conducted throughout the temperature range that the extinguisher is listed for, this operating temperature range will normally be shown on the unit, or the manual. During hotter periods an extinguisher guage is showing over-pressurized – on investigation the extinguisher was not over-pressurized – it was hot, and the reverse is true in the colder periods. Goto top of page

ABE Dry Chemical can be used anywhere.

No!There are a number of places where the use of ABE dry chemical is cannot be used. Risks involving Oxidizers – one of the more common places you may run into oxidizers would be in pool chemical supplies and waste water treatment facilities. If ABC dry chemical is used around these chemicals, a violent reaction may occur.

Aluminium – Mono-ammonium phosphate is acidic in nature. It will cause corrosion on untreated metal like any other acid would if it is not cleaned up quickly after the incident or discharge. The problem with aircraft is that there are so many places for the chemical to hide making complete clean up impossible. It would be necessary to take the airframe apart “rivet by rivet” in order to clean it properly. Without complete clean up, the airframe will corrode over time and may fail.

In addition to these cases where ABC dry chemical cannot be used, there are other cases where you should not use it. Cooking grease hazards should have only Class K extinguishers available in order to saponify the cooking grease and to cool the grease down safely (more on this later). ABC dry chemical will not work on these fires.

ABC dry chemical may have only a limited effect on deep seated Class A fires, or Class A fires that involve burning embers that “burrow” into the fuel (such as cotton bales, wood chip piles.) Mono-ammonium phosphate works on Class A fires by melting into a sticky, molten residue at about 350 deg. F. This residue sticks to burning embers and excludes oxygen, interrupting the combustion process. In a deep-seated fire like a cotton bale or a wood chip pile, the dry chemical will have trouble penetrating into the material where the burning embers are “burrowing”. Water mist, water spray or foam would be the choice for combating these types of fires. Goto top of page

Sprinklers or fixed systems – extinguishers not necessary

This is absolutely not true. Apart from the requirements of Standards. Sprinklers and fixed systems are important elements in any good fire protection plan and practice, but they should not take the place of fire extinguishers. Sprinklers may control a large fire and keep it from spreading to other parts of the building, but they lack the speed, versatility and mobility of extinguishers. Only hand portable extinguishers and wheeled extinguishers are capable of extinguishing fires quickly during the initial, incipient stages of a fire. They are the only devices that can handle hazards that are outside the design of a fixed system – i.e. a vehicle fire on a loading dock, a forklift fire in the yard, fires caused during remodeling or maintenance operations. There are also situations such as Class D hazards, flammable liquids under pressure and three-dimensional fires where sprinklers may actually have an adverse effect.

Fire Extinguishers, Fixed Systems Sprinklers, Smoke Detection and Alarm Systems, Building Codes and Fire Departments are all required in order to have a good Fire Protection Program that will handle any foreseeable hazard. Each element in the program is essential, each element has its place and each element cannot take the place of another. Goto top of page