Extinguisher Type Chart
"The Higher the Rating the better the Protection"
EXTINGUISHER PRODUCT INFORMATION SHEET
Portable Fire Extinguishers
Portable fire fighting equipment is designed to provide the user with an appliance to attend a small fire during its initial stage. When deciding to attack a fire, always designate another person to raise the alarm and obtain a back-up fire extinguisher. Portable fire extinguishers should beprovided in all buildings.
Types/Selection of fire extinguishers
There are a number of types of portable fire extinguishers available in Australia. Each type of extinguisher may be rated for one or more classes of fire. In some cases, particular extinguishers are not only considered ineffective against certain classes of fire, they can be dangerous in those circumstances. The Classes of fire are:
|
CLASS A
CLASS B
CLASS E
CLASS F |
Paper, Wood, Cardboard
Solvents, Paint, Petroleum, Methylated Spirits.
Electrical fires
Cooking oils and fats |
Water
Description: Red Rating 2A Use Class A Fire
Size 9.0Ltr
The FireBox Air/Water Extinguisher contains water under pressure and is to be used in an upright position. It is designed for use on carbonaceous solids such as wood, paper, rubbish or textiles, and has a discharge period of 60 - 100 seconds. Water extinguishers are unsuitable for flammable liquid fires.
Foam
Description: Red/Blue bandRating 2A : 20BUses Classes A & B Fires
Size 9.0Ltr
The FireBox Air/Foam Extinguisher contains an aqueous film-forming foam additive, and is to be used in an upright position. It is designed for use on flammable liquid fires such as petrol, oils and paint. This extinguisher must never be used on fires involving live electrical equipment.
Dry Chemical
Description: Red/White band Rating 1 to 6 A : 10 to 80B:EUses Classes A,B & E Fires
Sizes 0.75 to 9.0Kg
The FireBox Dry Chemical Extinguisher contains dry chemical powder and is suitable for fighting fires involving flammable liquids and live electrical equipment. The discharge period depends on the size of the extinguisher.
Carbon Dioxide CO2
Description: Red/Black band Rating 2 to 5B : E Use Class E Fires
Sizes 2.0Kg to 5.0 Kg
The FireBox Carbon Dioxide Extinguisher is especially effective on electrical fires because, being a gas; it does not leave any residues which might further harm the damaged equipment. (Carbon dioxide can also be used on class A fires when it is important to avoid water damage.
Wet Chemical
Description: Red/Oatmeal band Rating 1 to 2A : 3 to 4F Use Class F Fires
Size 2.0Kg to 5 Kg
The FireBox Wet Chemical Extinguisher contains a liquid alkaline extinguishing agent, and is specifically designed for use in kitchens on deep fryer fires involving fat and cooking oil. These extinguishers must never be used on fires involving live electrical equipment
Inside an Extinguisher-Technical Information
There are three essential elements involved in producing fire -- heat, oxygen and fuel. To put a fire out, you need to effectively remove one of these elements.
The best way to remove heat is to dump water on the fire. This cools the fuel to below the ignition point, interrupting the combustion cycle.
To remove oxygen, you can smother the fire so it is not exposed to air. One way to smother a small fire is to cover it with a heavy blanket
Removing the fuel is the most difficult approach for most fires. In a house fire, for example, the house itself is potential fuel. The fuel will only be removed once the fire has burned all of it up.
Fire extinguishers are sturdy metal cylinders filled with water or a smothering material. When you depress a lever at the top of the cylinder, the material is expelled by high pressure, similar to the way material is forced out of an aerosol can.
A siphon tube leads from the bottom of the fire-suppressant reservoir to the top of the extinguisher. A spring-mounted valve blocks the passageway from the siphon to the nozzle. At the top of the cylinder, there is a smaller cylinder filled with a compressed gas -- liquid carbon dioxide, for example. A release valve keeps the compressed gas from escaping. In Australia, we have Stored Pressure Extinguishers.
OPERATION
To use the extinguisher, you pull out the safety pin (this metal safety pin prevents the operating lever from closing accidentally) and depress the operating lever. The lever pushes on an actuating rod, which presses the spring-mounted valve down to open up the passage to the nozzle. The bottom of the actuating rod has a sharp point, which pierces the gas cylinder release valve.
The proper way to use the extinguisher is to aim it directly at the fuel, rather than the flames themselves, and move the stream with a sweeping motion.
Chemistry-Technical Information
Water
Water is the most common chemical for Class A Fires and is effective. Most water based extinguishers also contain traces of other chemicals to prevent the extinguisher rusting. Some also contain wetting agents which help the water bore deeply into the burning material and adhere better to surfaces. Water works to extinguish a fire by simply cooling it below the ignition point, although large amounts of water can also exclude oxygen. However, water will merely exacerbate other fire classes. For instance, water sprayed over burning liquid petroleum merely spreads the flames around. Similarly water sprayed on an electrical fire may cause the operator to receive an electric shock. (However, if the power can be safely disconnected and a carbon dioxide or halon extinguisher is not available, clean water will actually cause less damage to electrical equipment than will either foam or dry powders.)
Foams
Foams are used on Class F Fires. These are mainly water based, with a foaming agent so that the foam can float on top of the burning liquid to exclude oxygen. Ordinary foams are designed to work on nonpolar flammable liquids such as petrol (gasoline), but may break down too quickly in polar liquids such as alcohol or glycol. Facilities which handle large amounts of flammable polar liquids use a specialised "alcohol foam" instead. Alcohol foams must be gently "poured" across the burning liquid. If the fire cannot be approached closely enough to do this, they should be sprayed onto an adjacent solid surface so that they run gently onto the burning liquid. Ordinary foams work better if "poured" but it is not critical. Protein foam" was used for fire suppression in aviation crashes until the 1960's when "Aqueous Film-Forming Foam" (or AFFF). Carbon dioxide (later sodium bicarbonate) extinguishers were used to knock down the flames and foam used to prevent re-ignition of the fuel fumes. "Foaming the runway" can reduce friction and sparks in a crash landing, and protein foam continued to be used for that purpose, although FAA regulations prohibited reliance upon its use for suppression.
Dry Powder
ABE powder consists of monoammonium phosphate and/or ammonium phosphate. It is effective on Class A: B & E Fires .As well as suppressing the flame in the air, it also melts at a low temperature to form a layer of slag which excludes oxygen from the fuel. For this reason it is effective against class A fires unlike a Rating B:E only extinguisher. ABE powder is the best agent for fires involving multiple classes.
Wet Chemical
Most Class F extinguishers contain a solution of potassium acetate, sometimes with some potassium citrate or potassium bicarbonate. The extinguishers spray the agent out as a fine mist. The mist acts to cool the flame front, while the potassium salts saponify the burning cooking oil, producing a layer of soap over the surface. This solution thus provides a similar blanketing effect to a foam extinguisher, but with a greater cooling effect. The saponification only works on animal fats and vegetable oils, so class F extinguishers cannot be used for class B fires. The misting also helps to prevent splashing the blazing oil.
Carbon dioxide
Carbon dioxide is especially effective on electrical fires, Class E Fires, as being a gas; it does not leave any residues which might further harm the damaged equipment. Carbon dioxide (CO2) also works on Classes B and C Fires by displacing the less dense oxygen. This can be problematic in enclosed occupied spaces as we need oxygen too! Although carbon dioxide is exhaled in our own breath, in the high concentrations required to extinguish deep seated fires it is one of the most toxic extinguishing agents used. (Carbon dioxide can also be used on Class A Fires when it is important to avoid water damage, but in this application the gas concentration must usually be maintained longer than is possible with a hand-held extinguisher.)
"The Higher the Rating the better the Protection"
