Note for Guidance

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History of the Portable Fire extinguisher

Introduction.

A portable fire extinguisher is an active fire protection device to extinguish or control a fire, often in emergency situations. A typically portable fire extinguisher consists of a pressure vessel containing an agent that when discharged, can extinguish a fire. In order to use a fire extinguisher, you must first make sure it is suitable to the type of fire. If it is not a suitable type, it may not be effective or it may cause additional dangers. For example, water on a kitchen chip pan fire will sink into the hot fat and be rapidly converted to steam erupting the flaming fat over a wide area. Water on an active electrical fire might create an electric shock danger.

Over the years many very effective fire extinguishing agents have been discovered but they went out of favour because of the side effects and the main one was toxicity. Others have been superceded by more effective extinguishing agents with fewer side effects consequently the following pages there are many extinguishing agents that have not been used for many years or banned.

History

In about 200 BC, Ctesibius of Alexandria invented a hand pump able to deliver water to a fire and it is known that the Romans used bucket chains, buckets passed hand-to-hand to deliver water to the fire. Then, in the middle Ages, 'squirts' began to be used to apply jets of water to fires.

The squirt worked rather like a bicycle pump. The nozzle was dipped into water and about one litre was sucked up by pulling out the plunger. The charged squirt was then directed at the fire and the plunger pushed home to eject the water. Squirts were used on the 1666 Great Fire of London.

The first version of the modern portable fire extinguisher was invented by Captain George William Manby in 1819, consisting of a copper vessel of 3 gallons (13.6 litres) of pearl ash (potassium carbonate) solution under compressed air pressure.

Around 1912 Pyrene pioneered the carbon tetrachloride or CTC extinguisher, where the liquid was expelled from a brass or chrome container by hand pump, onto a fire. The sizes were usually of 1 imperial quart (1.1 L) or 1 imperial pint (0.6 L) capacity but also made in up to 2 imperial gallon (9 L) sizes. The CTC vapourised and extinguished the flames by interfering with the chemical reaction. This extinguisher was suitable for liquid and electrical fires and was popular in motor vehicles for the next 60 years. The vapour and combustion by-products were highly toxic and deaths did occur from using these extinguishers in confined spaces.

The late 19th century saw the invention of the soda-acid extinguisher, where a cylinder contained 1 or 2 gallons of water that had sodium bicarbonate mixed in it. Suspended in the cylinder was a vial containing concentrated sulphuric acid. The vial of acid was broken by one of two means depending on the type of extinguisher. One means involved the use of a plunger that broke the acid vial, while the second involved the release of a lead bung that held the vial closed. Once the acid was mixed with the bicarbonate solution, carbon dioxide gas would be expelled and this would in turn pressurize the water. The pressurized water was forced from the canister through a short length of hose and a nozzle. The acid was neutralised by the sodium bicarbonate.

Foam extinguisher consisted of the main body of the extinguisher filled with foam producing chemical and a second container filled with another chemical which reacts when it came into contact with the solution in the main cylinder. To operate you turned the extinguisher upside down and allowed the two solutions to mix, then hold your finger over the discharge nozzle and shake the extinguisher to ensure the solution was properly mixed then direct it at the fire.

Middle of the twentieth century the modern type of extinguisher appeared using different extinguishing agents. Manufacturers of extinguishers generally use some type of pressurized vessel to store and discharge the extinguishing agent. The fire extinguishers are pressurized with air to approximately 10 bar, five times a car tyre pressure, from a compressor. A squeeze-grip handle operates a spring-loaded valve threaded into the pressure cylinder. Inside, a pipe or dip tube extends to the bottom of the extinguisher so that in the upright position, the opening of the tube is submerged. The extinguishing agent is released as a steady stream through a hose and nozzle, pushed out by the stored pressure above it. Fig 1

Extinguishers of the "gas cartridge" type operate in the same manner, but the pressure source is a small cartridge of carbon dioxide gas (CO2) at 130 bars, rather than air. A squeeze-grip handle operates a spring-loaded device causing a pointed spike to pierce the disc that held back the pressure, releasing the gas into the pressure vessel. The released CO2 expands several hundred times its original volume, filling the gas space above the extinguishing agent. This pressurises the cylinder and forces the extinguishing agent up through a dip-pipe, out through a hose and nozzle to be directed upon the fire. This design proved to be less prone to leak down, loss of pressure over time, than simply pressurizing the entire cylinder. Fig 2

For water, foam, dry powder and wet chemical extinguishers, the extinguishing agents can either be put under stored pressure, or a gas cartridge expeller, however the stored-pressure type is more widely used. Dry powder generally use the CO2 cartridge method to prevent the powder being affected by moist air used for the stored pressure method.

In carbon dioxide extinguishers, the CO2 is retained in liquid form under 50 to 60 bar and is self-expelling, meaning that no other element is needed to force the CO2 out of the extinguisher. In halon units, the chemical is also retained in liquid form under pressure, but a gas booster, usually nitrogen, is generally added to the vessel.

The nozzles are the main difference; water has a circular nozzle which forms a solid jet which can penetrate to the heart of the fire. Foam has a miniature foam nozzle that aerates the foam solution and forms a floppy stream of foam that can be gently applied to the surface of the liquid. Dry Powder has an elliptical nozzle which spreads the powder and prevents air being entrained. Wet Chemical has a nozzle that creates a fine spray which allows you to apply the extinguishing agent gently. Carbon dioxide has a discharge horn which slows down the jet of gas and prevents air being entrained.

This handout provides a general overview and basic information on this topic. It may not apply to everyone, consequently to find out if this guide applies to you and to get more information on this subject, study all the relevant legislation, guides and British/European Standards. Also you should seek advice from an expert on the subject or your local Fire Safety Officer or Fire Safety Professional.

Merseyside Fire Liaison Panel. Permission is granted to print and photocopy this material for nonprofit educational uses.

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This page was last checked and modified on Saturday, 22 March, 2008 22:41