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Extinguisher Guide

There are a number of different extinguishing agents on the market, developed and designed to extinguish different types of fire. Fires are classified according to the combustible material involved.

Classes of Fire

Class A fires - are fires involving organic solids like paper, wood etc, as well as soft furnishings, fabric, textiles

Class B fires - are fires involving flammable liquids like petrol, oil or paints

Class C fires - are fires involving flammable gases

Class F fires - are fires involving cooking oil and deep fat fryers

Electrical equipment - for example computers, do not fit in to any of the above classifications but have also been considered in this article.

It is essential to know which extinguishing agent should be used on which class of fire.


Types of Extinguishers

Water Extinguishers

Water extinguishers are good for tackling fires involving burning paper, wood and soft furnishings, as the water soaks into the materials (Class A fires). This type of extinguisher does not leave a residue, but does have a comparatively low rating. Due to this more water is required to overcome their lacking in fire fighting power, making water extinguishers larger and heavier. It is important to remember that water is an electrolyte and conducts electricity. Care must therefore be taken with regards to accidental use on mains power. These problems can however be overcome by installing water extinguishers with additive. This type of extinguisher has a higher fire rating, which therefore reduces the weight of the extinguisher and removes the risk of self-electrocution.

Foam Extinguishers

Foam extinguishers are suitable for flammable liquids and areas where soft furnishings and carpets are present (Class A and B fires). Foam extinguishers are safe to use with regards to electrical risk. This type of extinguisher usually contains additives which can be hazardous to your health, making the cleaning process of the premises after the event of a fire more problematic. The foaming agent in most foam extinguishers is also harmful to the environment but these are gradually being replaced to meet incoming legislation.

CO2 (Carbon Dioxide) Extinguishers

CO2 extinguishers contain only pressurised CO2 gas and leave no residue. This type of extinguisher is suitable for use on fires involving burning liquids (Class B fires), but is also an excellent solution for quenching fires involving computer equipment and other electrical appliances as it does not cause damage to the electrical items and does not cause the system to short circuit. It is important to remember that when using CO2 extinguishers there is a possibility that once the gas has floated away the fire may reignite if the source of the fire is not removed (e.g. by switching off the power supply). Please be aware that CO2 extinguishers that are not fitted with double-lined frost-free swivel horns may cause your fingers to freeze to the horn during the deployment of the CO2 gas.

Powder Extinguishers

Powder extinguishers, also called ABC powder or dry powder extinguishers, are suited to fight class A, B and C fires. Powder extinguishers have a good fire fighting capacity, but this agent does not soak into materials and does not have a cooling effect on the fire. This could result in the fire reigniting, if it is not properly extinguished. Care must be taken when using powder extinguishers and they should not be used in small confined spaces where there is a risk of inhalation of the powder. The grain of the powder is incredibly fine and very mildly acidic, so unless all traces are removed it can gradually erode the material or surface it is contact with. For these reasons the choice of where to place these versatile extinguishers must be made very carefully with all factors taken into account.

Wet Chemical Extinguishers

Wet Chemical extinguishers are suitable for use with fires involving burning oil and deep fat fryers (Class F fires). These extinguishers come with a special application lance which lays a cooling layer of foam on top of the burning oil at low pressure, though smaller versions (e.g. 2 litres) usually feature only a nozzle. Alternatively a fire blanket can be placed over the pan containing the burning oil. The pan should then be left to cool down. NEVER carry the pan outside or lift the fire blanket after a short period of time to inspect the burning oil as introducing oxygen through this action could reignite the fire. NEVER use a pressurised water, powder or foam extinguisher on fires involving burning oils as the pressurised jet will cause the burning oil to be carried out of the pan onto surrounding surfaces causing more damage and a larger fire to tackle. Water jets are particularly dangerous if used on fat fires as the water will penetrate the oil and superheat in an instant, turning to steam and causing the fire to flair up.

Water Mist Extinguishers

Water Mist fire extinguishers are highly effective on class A, B, C and electrical fires. The unique design of the water mist extinguishers' supersonic nozzle creates a microscopic mist curtain, reducing the oxygen content. The low pressure of this mist curtain also makes them suited to small or shallow fat fires associated with domestic cooking. Water mist extinguishers have also been tested to ensure they are safe on live electrical equipment up to 1000V. The water mist extinguisher only contains de-ionised water which cannot conduct electricity.


Regulations and Maintaining your Extinguishers

By law, employers must provide their staff with adequate means of tackling a fire in the workplace. There is also a legal obligation for a competent person to annually service the fire extinguishers to standard BS 5306 part 3. In addition, all extinguishers must be maintained in working order and in good repair in between the services. This means that workplaces must also ensure that they carry out their own checks, at least monthly.

Monthly Visual Inspection

Check for any sign of tampering. This could include missing or broken tamper tags or pins. Look for any signs of discharge which could include water, powder or foam traces on the hose or horn of the extinguisher. Gauges showing low or high pressure (usually indicated by a red section). Any damage to extinguishers, rust, dents, missing parts, etc. Workplaces with a high risk of damage to their extinguishers such as those kept on haulage vehicles should be particularly vigilant. Any damaged extinguishers must be replaced immediately or repaired by a servicing company.

Competent Person

A competent person is defined by the British Standard as: a person with the necessary training and experience, with access to the relevant tools, equipment and information, manuals and knowledge of any special procedures recommended by the manufacturer of the portable extinguisher, to be capable of carrying out the relevant maintenance procedures of this standard. We recommend using a BFC or BAFE registered company which employs qualified technicians, who undergo refresher training every 3 years to keep their industry knowledge up to date.

Annual Maintenance

During the basic annual maintenance, the extinguisher technician carries out various procedures on the extinguishers depending on their make and type. Generally, the maintenance visit includes: Checking all extinguisher parts such as: valves, safety devices, gauges, and operating mechanisms. Checking that the pressure and weight is within the stated range. Issuing a Certificate of Inspection - a legal record of the maintenance carried out on the fire extinguishers to be kept by the customer and technician.

Extended Maintenance (Discharge and Refill)

Extended maintenance generally involves carrying out a test discharge on the extinguisher, checking internal and external parts, then recharging the extinguisher ready for use, if deemed safe by the engineer. BS 5306 - 3, states that water extinguishers, foam extinguishers, powder extinguishers and wet chemical extinguishers require an extended service every 5 years. CO2 fire extinguishers must have an overhaul & pressure test every 10 years. Most companies carry out a service exchange for CO2 and powder fire extinguishers due to be discharged. This entails exchanging your old extinguisher for a new or refurbished extinguisher. Buying new fire extinguishers from Budget-Fire may prove to be more cost effective than service-exchanging old units.

Fire Extinguisher Wall Signs

Each extinguisher must be accompanied by appropriate fire extinguisher wall signage. These signs indicate the type of extinguisher and give instructions about the use of the specific extinguishers.

Wall Mounting

All extinguishers should, where possible, be wall mounted on a suitable bracket or placed on a extinguisher stand. All our extinguishers are supplied with the relevant wall bracket. Extinguishers should never be used to prop doors open, especially fire doors. It is illegal to prop fire doors open in this way and they should remain shut unless an automatic fire door retainer has been fitted.

Further Information

This fire extinguisher guide is only a brief introduction. For further information please refer to: BS EN3 BS 5306 part 3 and 8, and the Regulatory Reform (Fire Safety) Order 2005.

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