It depends on the size of each floor, the number of floors and the fire risks. British Standard BS 5306-8 sets out how to work it out, and your fire risk assessment should confirm it.
Our Standard Advice
Our standard fire point is a 6 Litre Water Fire Extinguisher, plus a 2kg CO2 Fire Extinguisher where there's electrical equipment. Place fire points near the exits on each floor, and use the calculation below to work out how many you need.
A Different Approach: Service-Free (P50) Extinguishers
P50 service-free extinguishers take a different approach – a long-term, money-saving investment, with no annual engineer visits and a life of up to 20 years. Their water mist and fluorine-free foam models have nozzles that have passed the dielectric test, so they're safe if the spray accidentally reaches live electrical equipment. That means you won't usually need a separate CO2 alongside them – only where it's truly necessary, such as next to server rooms or large electrical installations. See Service-Free (P50) Extinguishers Explained.
Working Out the Number (BS 5306-8)
- Measure the floor area of each floor in square metres.
- Multiply it by 0.065. That gives the minimum total Class A rating for that floor.
- Each floor should have at least two Class A extinguishers with a combined rating of at least 26A. On a small upper floor under 100 m², one may be enough.
- Add extinguishers until you meet both the rating and the travel distances below.
Example: a 350 m² ground floor needs 350 × 0.065 = 22.75A, so two 13A water extinguishers (26A in total) cover it. A 300 m² first floor needs 19.5A – again, two 13A extinguishers. That's four Class A extinguishers in total. The rating is shown on each extinguisher's label.
Travel Distances
- No one should have to travel more than 30 metres to reach a Class A extinguisher.
- Where flammable liquids are stored or used, no one should have to travel more than 10 metres to reach a Class B extinguisher.
Electrical Equipment
- CO2 is only needed where there's electrical equipment. In an office with standard computers, a 2kg CO2 nearby will usually do.
- BS 5306-8 also calls for one at the mains intake or distribution board.
- Large machinery or three-phase (415-volt) equipment may need a 5kg CO2, kept within reach of the equipment.
Other Risks
Add the right type for any special risk: wet chemical and a fire blanket in a kitchen, foam (preferably fluorine-free) or powder where fuels or solvents are stored.
If you're not sure, we can talk you through it, or arrange a fire safety survey where an engineer visits and recommends exactly what you need.
Worth remembering… your fire risk assessment is what decides the equipment your premises need. This guide is general advice, not a substitute for it.
Not sure what you need? Get in touch with our team – we'll be delighted to help. No pressure. No sales patter.