A Guide to the Different Classes of Fire in the UK from A to F
A guide to the classes of fire in the uK from a to f
All fires have the potential to endanger lives and destroy businesses, therefore it is extremely important to recognise the differences between the various types of fire, known as ‘class’.
The ‘class of a fire’ is determined by the type of fuel that is burning, and this allows appropriate fire extinguisher media to be identified.
Your fire risk assessment will identify the need for specific fire extinguishers in relation to the hazards on the premises. Thorough knowledge of the characteristics of the various types of extinguisher is therefore required by the competent person carrying out the fire risk assessment.
The Legal Position
Under the Regulatory Reform (Fire Safety) Order 2005 (FSO) the Responsible person (RP) has a general duty to take general fire precautions (Article 8) and as defined under Article 4(1)(d) ‘measures in relation to the means for fighting fires on the premises;’
This is further defined in Article 13;
‘(1)……. The responsible person must ensure that:
a) The premises are, to the extent that it is appropriate, equipped with appropriate firefighting equipment….. and
b) Any non-automatic firefighting equipment so provided is easily accessible, simple to use and indicated by signs.
(2) for the purposes of Paragraph (1) what is appropriate is to be determined having regard to the dimensions and use of the premises, the equipment contained on the premises, the physical and chemical properties of the substances likely to be present and the maximum number of persons who may be present at any one time.’
Employers must provide the correct fire extinguisher suitable for the type of fire likely to occur on their premises.
Classes of Fire
There are currently six classes of fire i.e., Class A, B, C, D, Electrical and F. Fires are classified according to the material that ignites the fire.
Below we provide a brief overview of each class of fire and a Fire Extinguisher Classification Chart.
Class A fires - Combustible materials:
Caused by flammable solids, such as plastics, wood, paper, straw, coal, textiles, furniture, etc. Most of these materials are organic in nature (sometimes known as ‘carbonaceous materials’).
Class A fires are probably the most common type of fire and they can spread quickly if there are enough combustible materials, oxygen, and heat to sustain the fire. Most commercial and industrial premises are likely to contain a large number of common combustibles, so preventing Class A fires requires knowledge, vigilance and regular premises inspection to ensure fire hazards are kept to a minimum.
The appropriate extinguishers used to tackle a Class A fire include water, foam, dry powder and wet chemical extinguishers.
Class B fires - Flammable liquids:
Such as petrol, diesel, oils, turpentine, paraffin, paint, ethanol, methanol, etc.
Class B fires are incredibly dangerous and can occur in any area where flammable liquids are stored or used such as garages, construction sites, warehouses, hospitals, and laboratories.
Flammable liquids have a low flash point so they burn easily when an open flame or other ignition point is introduced. A match, lighter or spark can ignite the vapours of a flammable liquid, so proper storage is required to minimise the chances of a Class B fire occurring.
Businesses should limit the amount of flammable liquids present as far as possible, and these should be kept well clear of any source of ignition. Open flames should never be introduced to an area where flammable liquids are stored.
The appropriate extinguishers used to tackle a Class B fire include CO2, foam and dry powder extinguishers.
Class C fires - Flammable gases:
Such as propane, butane, methane, natural gas, hydrogen, etc.
Flammable gases are highly volatile and pose a major fire and explosion risk, therefore in any industrial or commercial area where flammable gases are used, they should be kept stored in a secure location that is strictly monitored and kept clear of open flames.
The concentration of flammable gases in the air will dictate the potential fire hazard, and even small or isolated leaks of these gases can lead to quick ignition if an open flame or igniter is introduced.
The appropriate extinguisher used to tackle a Class C fire is a dry powder extinguisher.
Class D fires - Combustible metals:
Fuelled by ignited metals such as magnesium, aluminium, lithium, titanium, potassium, etc.
Metal-based fires are not common as not all metals are flammable. Due to the excessive temperatures needed to ignite flammable metals these types of fires are often extreme in nature, Class D fires must be tackled with a specific dry powder extinguisher (L2 or M28) that include graphite, copper, and sodium chloride-based powders. The main risks for Class D fires are the smaller deposits of metal, such as shavings or powders. If metal shavings or finer deposits of flammable metals are common in the workplace, regular cleaning should be carried out to limit the concentration of metals at any one time. Sparks or open flames should also be kept clear of these areas. Sheet metal and thick, solid metals are less of a fire hazard, as a result, industrial settings where metalwork, such as cutting, is performed are at greater risk of Class D fires.
The appropriate extinguishers used to tackle a Class D fire include L2 or M28 (specialist) dry powder extinguishers.
Electrical fires (Class E is not used, instead the symbol of an electric spark is displayed)
Caused by electrical equipment such as TV’s, computers, faulty wiring, frayed cables, broken electrical appliances/tools, short circuits, overloading multi-adaptor plug sockets, hairdryers, extension leads, etc. Once the electrical item is removed, the fire changes class.
Electrical fires are not given their own full class, as they can fall into any of the other classifications. After all, it is not the electricity that is burning but the surrounding material that has been set alight by the electric current.
Electrical fires can be very common, with potential hazards present in virtually every commercial or industrial setting. If an electrical item or appliance is showing signs of a fault or deterioration, the power to the item should be cut immediately and the appliance should be kept out of use until it is repaired or disposed of.
The first step when fighting a fire caused by electricity is to switch the equipment off. As water conducts electricity, spraying an electrical fire with water can cause the current to travel back up the stream and potentially electrocute the operator. In addition, any water-based extinguishers used on electrical equipment should be dielectrically tested and certified to ensure that you can extinguish the fire safely, even if the power supply is left on. It must be remembered that certain electrical apparatus maintain a lethal charge for some time after they have been switched off.
The appropriate extinguishers used to tackle a Class E fire include CO2 or a dry powder extinguisher.
Class F fires - Cooking oils:
Such as fats, cooking oils, grease, etc.
Class F fires consist of cooking oils and fats that have been ignited. The high flash point of cooking oils and fats and the extremely high temperatures necessary to cause a blaze with these materials, it has been designated its own fire class.
These kinds of fires are most common in restaurants and commercial kitchens.
A common cause of Class F fires relates to deep fat frying; oil can be left to cook for too long, or in too great a quantity. Deep fat frying is the leading cause of accidental fires in kitchens, so great care is required at all times. Most often, they occur when pans containing oils are left unattended or are not carefully monitored. Signs of a potential Class F fire, such as seeing or smelling smoke, means you should turn the heat off immediately before the oil reaches too high a temperature and ignites. Prevention is incredibly important, and busy environments like large commercial kitchens should enforce strict fire safety standards.
A fire blanket is often the best solution for smaller cooking oil/fat fires, eradicating the need to clean up any debris from the use of chemical suppressants.
The appropriate extinguisher used to tackle a Class F fire is a wet chemical extinguisher.
Fire Extinguisher Chart
Fire Risk Consultancy Services have the knowledge and experience to assist your business to comply with all legal requirements surrounding Fire Safety including the legislation regarding Fire Alarms. Be sure to read our accompanying guides: How Many Fire Extinguishers Do I Need?, Types of Fire Extinguisher, Siting of Fire Extinguishers, Chrome Fire Extinguishers, P50 Fire Extinguishers AND Fire Alarm System Types, Emergency Lighting, Fire Door Regulations, Fire Safety Signs, also published on this site.
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