What Do Fire Extinguisher Ratings Mean?
Short answer
The letters and numbers on a fire extinguisher tell you what classes of fire the extinguisher is suitable for and its tested firefighting performance.
For example, a rating such as 10A:80B:E means the extinguisher has achieved specified performance ratings for Class A and Class B fires and is also suitable for use where energised electrical equipment is involved.
In Australia, extinguisher classifications and performance ratings are covered by AS/NZS 1850.
What do the numbers and letters on a fire extinguisher mean?
The letters identify the classes of fire the extinguisher is designed to deal with.
- Class A — ordinary combustible materials such as wood, paper, cardboard and textiles
- Class B — flammable and combustible liquids such as petrol, oils, paints and solvents
- Class C — flammable gases such as LPG, propane and acetylene
- Class D — combustible metals such as magnesium and aluminium
- Class E — fires involving energised electrical equipment
- Class F — cooking oils and fats
The numbers are performance ratings based on standardised test fires.
Classes A, B and F can carry numerical performance ratings. Classes C, D and E do not use numerical ratings.
A higher number generally indicates greater tested firefighting performance within that particular fire class.
What does a rating like 10A:80B:E mean?
A rating of 10A:80B:E can be broken into three parts.
10A means the extinguisher achieved a 10A performance rating against the applicable Class A standard test fire.
80B means the extinguisher achieved an 80B performance rating against the applicable Class B standard test fire.
E indicates that the extinguisher is suitable for use where energised electrical equipment is involved.
The numbers are not measurements of litres, kilograms, gallons or square footage. They are performance ratings achieved during standardised extinguisher testing.
This means the rating provides different information from the physical size of the extinguisher.
A 1kg, 2.5kg, 4.5kg or 9kg extinguisher describes the quantity of extinguishing agent, while the fire rating describes the extinguisher's tested firefighting performance.
What do the fire classes A, B, C, D, E and F mean in Australia?
Each fire class represents a different type of fuel or hazard.
Class A includes ordinary combustible materials such as timber, paper, cardboard, fabrics and many plastics.
Class B includes flammable and combustible liquids such as petrol, diesel, oils, paints and solvents.
Class C includes flammable gases such as LPG, propane, butane and acetylene.
Class D includes combustible metals and generally requires specialised extinguishing agents.
Class E relates to fires involving energised electrical equipment such as switchboards, computers, electrical appliances and machinery.
Class F includes cooking oils and fats, particularly those found in commercial kitchens and deep fryers.
The extinguisher must be suitable for the actual fire risk present.
For example, an office may contain large amounts of paper, cardboard, furniture and textiles as well as electrical equipment. Providing only COâ‚‚ extinguishers may address the electrical risk but leave the Class A combustible-material risk inadequately covered.
Does a higher fire extinguisher rating mean it is better?
Not necessarily.
A higher numerical rating indicates greater tested firefighting performance for that particular class of fire, but extinguisher selection involves more than simply choosing the highest rating available.
The extinguisher also needs to suit the hazards present, the location, the required coverage and the people who may need to use it.
A larger extinguisher can provide greater firefighting capacity, but it is also heavier and may be more difficult for some people to carry and operate.
For example, in an office environment, appropriately located 4.5kg ABE extinguishers may be more practical for staff to handle than relying on a much heavier 9kg extinguisher.
The aim is to provide suitable firefighting capacity while ensuring the equipment remains practical for the people who may need to use it.
How do I know whether the extinguisher rating is suitable for my workplace?
The extinguisher needs to match the fire risks present in the area it is intended to protect.
This means considering:
- ordinary combustible materials such as paper, timber and textiles
- flammable or combustible liquids
- flammable gases
- energised electrical equipment
- cooking oils and fats
- the required firefighting performance
- the size and weight of the extinguisher
- the people who may be expected to use it
- the location and accessibility of the extinguisher
Extinguisher selection and placement are addressed by AS 2444.
For Class A risks, the maximum travel distance from any point in the protected area to the nearest suitable extinguisher should generally not exceed 15 metres.
This is a travel-distance requirement. It does not simply mean that extinguishers should be positioned 15 metres apart.
Once fire extinguishers are installed, their ongoing routine servicing and maintenance is addressed by AS 1851-2012.
The type, rating, placement and ongoing condition of the extinguisher all need to remain appropriate for the risk it is intended to control.
Ratings are only part of the picture. Our guide on the different types of fire extinguishers explains what each extinguisher type is, the colour bands used to identify them and which type suits which workplace risk.
And if you are unsure what the broader fire safety requirements in NSW actually are, our guide on the requirements for fire inspections in NSW explains what section 81A and AS 1851-2012 require of building owners.