A portable fire extinguisher by definition is an item of equipment for the purpose of extinguishing a fire. The reality is however that a portable fire extinguisher is effective only for the type and size of a fire that it is rated for.
Portable fire extinguishers are generally provided as "first attack" units in fire fighting and should be used only in early stages of fire before the fire grows to a stage that is beyond the capacity of the extinguisher. There are broadly six types of fire extinguisher;
Most portable fire extinguisher selection charts will also show the Vaporising Liquid1 . type fire extinguisher (red with a yellow band). For the sake of completeness, we list this fire extinguisher, however for practical terms the Vaporising Liquid Extinguisher is no longer available for commercial or retail purchase in Australia. There are some circumstances such as aviation or marine where the use of these extinguishers may be permitted however these applications are limited.
The selection of an extinguisher must be made with the class of fire in mind.
The first record of a fire extinguisher was patent lodged in 1723 by English scientist Ambrose Godfrey. In the following 300 years there have been literally hundreds of iterations and variations on the basic design for a fire extinguisher.
If you distil all of the variations down you will find five components common to almost every type of extinguisher manufactured throughout history;
Modern fire extinguishers continue to retain these common components, however improvements in technology have resulted in improvements to the performance (capacity and rating) of an extinguisher.
Earlier in this series, we outlined the foundation for fire chemistry. Combustion (fire) is a sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the by-products of combustion being; heat, smoke & electromagnetic radiation (light).
There are four elements that contribute to provide the correct environment for a fire to start and be sustained. These four elements are; Fuel, Heat, Oxidant, and the Chemical Reaction (Oxidation).
The effective removal of any one of these essential elements will result in the fire being extinguished. In simple terms, a fire extinguisher works by influencing, eliminating or the ongoing effect of one or more of these four elements.
Fires are classified according to the type of fuel and if live electrical equipment is present. The classification of a fire is important, as it influences the selection and use of the correct extinguisher required to extinguish a fire. The six classes of fire are:
These classes of fire are also illustrated by a pictogram to assist people quickly identify the type of fire.
As we stated earlier, there are broadly six types of extinguisher; Water, Foam, Wet Chemical, Dry Chemical Powder, Carbon Dioxide and Vaporising Liquid (Note: The retail purchase of vaporising liquid fire extinguishers is no longer available due to their environmental impact). The selection of a fire extinguisher for a given classification of a fire is assisted by the colour coding of extinguishers according to their type.
Portable fire extinguishers are distinguishable by their labels and their colouring. In 1997 the standard colour of portable fire extinguishers changed. From this date, extinguishers supplied to the market are required to be painted red or be polished stainless steel. As this change was relatively recent it is still common to find extinguishers using both Pre 1997 and Post 1997 extinguisher colour schemes.
There is no one type of fire extinguisher that is universally acceptable for all classes of fire. Careful consideration needs to be given to the selection of the most suitable type of fire extinguisher, or combination of fire extinguishers for each application.
A water based extinguisher also referred to as a Stored Pressure Air-Water fire extinguisher is an extinguisher that is filled with water which is stored under pressure (normally by air). These extinguishers are only appropriate for use on Class A fires.
A water extinguisher is effective because it cools the fire, interrupting the exothermic reaction of a self-sustaining fire.
A water extinguisher operates when water, stored under pressure and contained within the extinguisher container is expelled after the valve, operated by a hand-held trigger is depressed.
There are several types of dry chemical powder fire extinguisher, the two main types are;
Note: Special powders are available to extinguish fires involving Class D combustible metals.
Dry chemical powder fire extinguishers are effective because they interrupt the oxidation process.
Dry-chemical powder is stored under pressure inside the extinguisher cylinder and is expelled when the hand-held trigger valve is depressed.
Carbon dioxide fire extinguishers are useful in protecting against fire when an inert, electrically non conductive, gas is desirable and where clean up from the agent must be minimal. Carbon dioxide extinguishers contain liquid CO2 that is expelled as a gas. Carbon dioxide blankets a fire, because of its heaviness, relative to air. It acts by preventing oxygen from getting to the fire, the result, the burning fuel deprived of the oxygen.
Carbon dioxide extinguishers are effective against Class “B” and “C” fires. Unlike other chemicals, CO2 does not leave a harmful residue and does not adversely affect the environment. It also poses very little danger to electronics and is effectively employed in laboratories, computer rooms, and other areas with sensitive electrical and electronic equipment.
An Air-Foam Fire Extinguisher is a versatile and effective solution for combating Class A and B fires, such as those involving wood, paper, flammable liquids, and gases.
This extinguisher releases a foam substance that works by smothering the fire and preventing it from spreading, and creates a barrier between the fuel and the source of ignition, helping to reduce the risk of re-ignition.
In addition, the air pressure helps to disperse the foam over a wider area, making it ideal for quickly and effectively tackling larger fires.
With its simple and reliable design, the Air-Foam Fire Extinguisher is a valuable tool for any workplace, home, or vehicle where the risk of fires is present.
A Wet Chemical Fire Extinguisher is a must-have for any commercial kitchen or cooking area.
Specifically designed to combat Class F fires involving cooking oils and fats, this extinguisher releases a fine mist that quickly cools and blankets the fire, cutting off its oxygen supply and preventing re-ignition.
The wet chemical agent also reacts with the oil or fat to create a soapy layer that helps prevent re-ignition, making it a highly effective and reliable option for any kitchen or cooking space. With its easy-to-use design and proven effectiveness, the Wet Chemical Fire Extinguisher is a smart investment in fire safety for any cooking environment.
Fire extinguishers contain an agent that is expelled from the extinguisher help to try and extinguish a fire.
The agent in each of the extinguishers explained in this document is stored under pressure. The valve is operated when the hand-held trigger is depressed.
Some fire extinguishers are also fitted with a pressure gauge that provides a visual indication of the extinguishers pressurised state. Gauges may illustrate a numerical value or a colour coded pressure range where green illustrates the extinguisher is pressurised and is in a state of readiness.
Fire extinguishers complying with Australian Standards are marked with a classification and rating, determined in accordance with Australian Standard AS 1850.
Extinguishers are rated by their performance and suitability for a particular class of fire, i.e. a typical water extinguisher may be marked 2A and a typical dry chemical extinguisher marked 2A:40B:E.
The number before the letter is a measure of the relative performance within the respective class as follows:
The higher the number , the more effective the extinguisher is for the nominated class of fire. When a fire extinguisher is rated for more than one class of fire, it is expressed in alphabetical order, i.e. 2A:40B:E.
A common misconception is that two fire extinguishers of equal mass (Kg) or volume (Litres) have the same rating.
Extinguishers are subjected to a range of standardised tests to determine their suitability and rating, in accordance with the requirements of the building Code of Australia and local authorities having jurisdiction. The rating of a fire extinguisher is required to be prominently displayed on the side of each extinguisher.
Generally the Building Code of Australia as well as various State and Territory legislation establishes the selection, location and distribution of fire extinguishers used in the community. Australian Standard AS 2444 is generally referenced in whole or in part by these legislative documents and provides further details on the selection, and location of fire extinguishers. AS 2444 is subordinate to these legislative documents and care should be taken when providing advice as to extinguisher requirements based solely on AS 2444.
Where required, fire extinguishers should be installed in a conspicuous and readily accessible position, supported by a substantial hook or bracket mounted not more than 1.2 metres above the floor (‘hip height’).
In addition, portable fire extinguishers should not be located in positions where access could present a hazard to a potential user. Where practicable, they should be located along normal paths of travel and near exits.
Most fire brigades or authorities having jurisdiction have guidelines for the selection and location of portable fire extinguishers to compliment the Building Code of Australia and Australian Standard AS2444.
There are two basic types of signage associated with portable fire extinguishers, a red, rectangular sign with a white pictorial of a fire extinguisher known as a “Location Sign” and an optional circular identification disc, specifying contents and type of fire on which the extinguisher is to be used.
The location sign should be positioned directly above the fire extinguisher, the bottom edge of which is not less than 2 metres above the floor. (AS 2444:2001 clause 3.3.4).
The optional identification sign should be placed immediately above the fire extinguisher (below the location sign).
After carefully selecting the correct type of fire extinguisher or combination of extinguishers for the right class of fire, a first responder should undertake the following;
There is an extensive array of Australian and New Zealand (AS/NZS) Standards that exist for the classification, rating, performance testing and requirements for portable fire extinguishers. The following list sets out some of these Standards;
All portable fire extinguishers are subject to periodic inspection, tests and preventative maintenance activities in accordance with Australian Standard AS1851. This Standard prescribes specific intervals, criteria or events when an extinguisher should be maintained.
The frequency of these inspections is recorded on the maintenance record (a yellow tag, securely fixed to the fire extinguisher) by stamping or marking a number to represent the maintenance activity performed as follows;
As most fire extinguishers are pressure vessels, they may also be required to be discharged, inspected and tested by an approved and licensed facility for any condition that is likely to render the vessel dangerous or unsafe.
Portable fire extinguishers may be used as the first response to most common classes of fire. In most commercial buildings, they are located throughout a building to provide occupants with the facilities to respond to a fire in its early stages.
In a domestic situation, households should be equipped with both a Dry Chemical Powder, Class AB(E) fire extinguisher and a fire blanket.
Fire extinguishers require periodic maintenance and should be maintained in accordance with Australian Standard AS1851.