Fire Extinguishers Selection

fire extinguishersThe blog covers the different types of fire extinguishers and their uses and limitations. Fire extinguishers are provided to aid escape from a building and should primarily be used for this purpose. The only other time fire extinguishers should be used is to tackle a small fire if the user feels safe and confident to do so. However, this must only be done after the fire alarm has been raised and the fire and rescue service called.

It must also be remembered that using the wrong type of fire extinguisher on a fire can result in making the fire worse and putting lives in danger.

Fire Extinguishers Selection

Classes of fire

There are a number of classes of fire. Their purpose is to help identify the right type of extinguisher depending on the materials that are alight. All fire extinguishers carry a pictogram to identify the types of fires it can be used on. Some fire extinguishers only contain one pictogram, whilst others have two or more. The pictograms are intended to help anybody to select the correct extinguisher to use on the right type of fire, and are harmonised throughout Europe.

The classes of fire are as follows:

  • Class A – solids, such as paper, wood and plastic;
  • Class B – liquids, such as petrol, solvents, alcohol;
  • Class C – gases, such as propane and acetylene;
  • Class D – metals, such as magnesium and sodium; and
  • Class F – cooking oil.

Fires in electrical equipment are not specifically given their own classification but those fire extinguishers appropriate for use on electrical fires are also identified with a specific symbol.

Fire extinguishers- Types

Portable fire extinguishers in the UK have in the past been manufactured to a British Standard which gave several options for the colour. However, a harmonised European Standard was published in May 1996. This, standard BS EN 3: 1996: Portable fire extinguishers, allows only one option. That is that all fire extinguishers should be red in colour but a zone of up to 10% of the external area may be coloured to indicate the type of extinguishing medium.

The colour code for the band on the fire extinguishers is listed below:

  • foam – cream;
  • dry powder – blue;
  • carbon dioxide – black;
  • water – red; and
  • wet chemical – yellow.

Using fire extinguishers

When using any fire extinguisher the PASS method should always be followed.

P – pull the pin;

A – aim the extinguisher hose or horn;

S – squeeze the handle; and

S – sweep the hose or horn.

Fully discharge the whole extinguisher; even if the fire goes out before the extinguisher has been fully used up, there may be sufficient heat for re-ignition to occur.

If you fully discharge an extinguisher and the fire has not gone out never use a second extinguisher; it is time to evacuate at this point.

When using fire extinguishers always keep the exit behind you where possible; this way if the fire grows you will be able to turn away from the fire and evacuate

Siting of fire extinguishers

Fire extinguishers are commonly sited conspicuously on escape routes so that in the event of fire they are easily accessed. Typical locations are corridors, stairways, lobbies, landings and room exits.

There should be no more than 30m travel distance from any point in a building to an extinguisher, taking into account any obstructions such as tables and chairs.

Fire extinguishers should also be provided to deal with specific risks that are highlighted by the fire risk assessment. For example, a computer room should be provided with a carbon dioxide or dry powder extinguisher, a kitchen with a fire blanket or wet chemical extinguisher, and a flammable liquid store with a foam or powder extinguisher.

Fire Extinguishers- Selection

A brief summary of when to use each type of fire extinguishers follows, arranged by class of fire. Class D is excluded, as metal fires require the use of specialist powders and specific training will need to be given to any member of staff expected to use a class D fire extinguishesr.

9.6.1 Fires involving solids

Fires involving solids such as paper, wood or cloth (Class A) are best dealt with using water, since it has the most efficient cooling action. Water firefighting equipment can take the form of fire extinguishers (red, or with a red indicating zone), hose reels and fire buckets.

The extinguisher jet should be directed at the base of the flames and moved from side to side. Water must not be used on or near electrical equipment or flammable liquids.

Water can only be used on Class A fires, because:

• if used on a Class B liquid fire, it can spread the liquid causing the fire to get worse;

• if used on a Class C gas fire, it can cause an explosion;

• if used on a Class D metal fire, it can react violently with the burning metal;

• if used on an electrical fire, it can lead to electrocution of the operator; or

• if used on a Class F cooking fats fire, it can react violently with the burning fat or oil.

Foam, wet chemical and powder fire extinguishers can also be safely used on Class A fires but are likely to be less effective as they have less of a cooling action.

Fires involving liquids

Fires involving liquids (Class B) can be extinguished by smothering or otherwise removing the oxygen supply using foam (cream colour on extinguisher), dry powder (blue) or carbon dioxide fire extinguishers (black). Foam is less effective when the fire is not in a container as it works by forming a blanket over the burning liquid and smothering it. Powder offers quick knock down of a fire, but if used outside it could be blown away allowing the fire to re-ignite. Under no circumstances should water be used on a liquid fire.

Fires involving gas

In the event of a fire involving gas (Class C), the supply should be turned off (if it is safe to do so), the alarm raised and the premises evacuated. If the flames are extinguished without turning off the supply, an explosion may result if the spreading gas is reignited.

No attempt should be made to tackle a fire involving gas cylinders, such as LPG or acetylene. The volume of such items should be kept to a minimum and be stored in accordance local written policies and procedures. Further guidance can be obtained from the Health and Safety Executive (HSE). Storage areas should also be signed to assist the fire service in the event of an incident.

Fires involving cooking oils

Wet chemical fire extinguishers have a yellow as its identifying colour and works by turning the top layers of oil (Class F fires) into a soap-like substance, thereby preventing the flammable vapours reacting with oxygen to continue the burning process. The wet chemical is applied via a lance which gives a gentle application to offer the operator an element of protection.

Under no circumstances should water be used on a cooking oil fire as it will not extinguish the fire but potentially cause the oil to erupt violently spreading the fire and injuring the operator.

Fires involving electrical equipment

Fires involving electrical equipment can be tackled using carbon dioxide or dry powder, although the latter is less efficient. Even though these do not conduct electricity, the current should still be turned off first, if at all possible, which may help extinguish the fire.

Water and foam should not be used on or near live electrical equipment as they both conduct electricity, which could be fatal to the extinguisher user.

Fire Safety Risk Management can help with the selection, supply, sitting and servicing of your fire extinguishers to ensure compliance with fire safety legislation.

 

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