In this blog, we’ll answer some of the most commonly asked questions around the classification of fire and types of fire extinguishers in the context of the workplace.
Why do I need to understand the different classes of fire that may occur in the workplace?
When a fire breaks out at work, being able to correctly identify the class of fire is essential to being able to successfully extinguish that fire. That’s because different types of fires require different types of extinguishers. In fact, using the wrong extinguisher on a fire can be dangerous. For example, using a water extinguisher on an electrical fire can result in electrocution.
What is the most common class of fire in the workplace?
Class A fires are the most common type of fire. These fires are fuelled by common combustible materials like paper, cardboard, wood, textiles, rubber, plastic, and litter, which can be found in most workplaces and homes.
What is the least common class of fire in the workplace?
Class D fires are generally the least common class of fire. This is because Class D fires are fuelled by combustible metals like magnesium, titanium, lithium, and potassium, which are not commonly found in ordinary home or workplace settings. In addition, Class D fires most commonly ignite when a heat source or spark comes into contact with fine metal shavings or powder, making these fires more likely in the context of machining, manufacturing, and scientific laboratories.
What type of fire extinguisher do I need at my workplace?
Which fire extinguishers you need to supply at your workplace depends on the classes of fire most likely to occur. It’s also important to consider how many extinguishers you need, where they should be located, and the different sizes of extinguishers available. See our blog Choosing the Right Fire Extinguisher for Your Workplace for more information.
How do I tell the different types of extinguishers apart?
While all fire extinguishers are red, different fire extinguisher types are identifiable by their colour-coded labels. The contents of the extinguisher will also be printed on the label.
- Water extinguishers have a predominantly red label
- Foam extinguishers have a predominantly cream label
- Carbon dioxide extinguishers have a predominantly black label
- Dry chemical powder extinguishers have a predominantly blue label
Which extinguisher should be used on a Class A fire?
Water extinguishers, which have a predominantly red label, are recommended for extinguishing Class A fires (fires fuelled by ordinary combustible materials like paper, wood, cardboard, textiles, etc.). Water extinguishers work by creating a cooling effect that reduces the temperature of the burning material to below its ignition temperature.
Which extinguisher should be used on a Class B fire?
Foam fire extinguishers, which have a predominantly cream label, are recommended for extinguishing Class B fires (fires fuelled by flammable liquids and gases).
How foam extinguishers work:
- The foam absorbs heat from the fire, creating a cooling effect.
- The foam creates a blanket over the surface of the burning liquid, which stops the fuel from vaporising.
- The blanket of foam creates a barrier between the fuel and the oxygen in the air, smothering the fire and preventing it from re-igniting.
Why should water extinguishers never be used on Class B fires?
Class B fires are fuelled by flammable and combustible liquids and gases, such as petrol, alcohol, and oil lacquers. If a water extinguisher is used on a fire fuelled by these liquids, you may actually cause the fire to spread. This is because water is heavier than most combustible liquids, which means that the burning liquids will flow over the surface of the water, continuing to burn.
Which extinguisher should be used on a Class C fire?
Class C fires (electrical fires) are best extinguished with a carbon dioxide (CO2) extinguisher. CO2 fire extinguishers can be recognised by their predominantly black label. Because CO2 is heavier than air, discharging a CO2 extinguisher onto a fire forms a dense cloud of CO2 that displaces the air surrounding the fire. This reduces the amount of oxygen that can reach the fuel, starving the fire. Water should never be used on a Class C fire due to the risk of electrical shock.
Another safe way to extinguish a Class C fire is to de-energise the circuit (switch off the electricity supply) and then attack the fire as either a Class A or B fire, depending on the fuel.
Which extinguisher should be used on a Class D fire?
Class D fires (fires involving combustible metals) should be extinguished with a specially formulated DCP (dry chemical powder) extinguisher. These extinguishers deliver a stream of finely ground particles or powder onto the fire. DCP extinguishers have a predominantly blue label.
How DCP extinguishers work:
- The powder interrupts the chemical chain reaction necessary for combustion.
- The dry chemical powder forms a powder layer over the fire, thus smothering the fire. Because no cooling takes place, there is a possibility of re-ignition.
What is the best way to extinguish a Class K fire?
Class K fires are most commonly found in kitchens as they are fuelled by cooking oils and fats. The most effective way to extinguish a grease pan fire is by using a fire blanket. Fire blankets are made from woven glass fibre fabric sheets and an inner layer of fire-retardant film. When placed over a grease pan fire, the fire blanket cuts off the oxygen supply to the fire, thereby smothering the fire. Alternatively, a CO2fire extinguisher can be used to extinguish a Class K fire.
Yes, all firefighting equipment, including fire extinguishers, must be serviced by a SABS-approved company on an annual basis. This is a legal requirement laid out by SANS codes and local fire safety by-laws. A certificate of firefighting equipment servicing compliance must be issued by the servicing company and kept on record. First Aid, Fire and Safety Training (FAFST) is a registered SABS firefighting equipment servicing company. Contact us to book fire equipment servicing from one of our SAQCC-registered technicians.
Where can I buy firefighting equipment in South Africa?
First Aid, Fire and Safety Training (FAFST) supplies firefighting equipment countrywide, including:
- Fire extinguishers
- Hose reels
- Fire blankets
- Fire alarms (manual alarms)
We also offer on-site fire equipment inspections to help you identify what’s missing from your firefighting equipment setup. FAFST also offers fully accredited OHS Firefighting training.
