A small fire is easy to put out if you have the right equipment close at hand. A few minutes later, the same fire can fill a building with smoke. A fire extinguisher is the tool that can stop a small fire from growing, but only if there are enough of them, in the right places, and of the right type.
Enter the floor area and the number of floors below, and the calculator will show how many extinguishers to start with.
How many fire extinguishers do you need?
The calculator uses a simple guideline based on BS 5306-8. It works out the number per floor, then multiplies by the number of floors.
Extinguishers per floor = the larger of 2, or floor area / 200 m2 (rounded up)
Total = extinguishers per floor x number of floors
So the rule is one extinguisher for every 200 square metres of floor area, and never fewer than two on any floor. The reason for the minimum of two is that one extinguisher may be on the other side of the fire, or may fail, so you need a second one in another place.
Worked examples
A small shop of 120 m2 on one floor. 120 / 200 = 0.6, which rounds up to 1. But the minimum is 2 per floor, so the shop needs 2 extinguishers.
An office building with 3 floors of 450 m2 each. 450 / 200 = 2.25, which rounds up to 3 per floor. 3 x 3 = 9 extinguishers in total.
A warehouse of 1,500 m2 on one floor. 1,500 / 200 = 7.5, which rounds up to 8. The warehouse needs 8 extinguishers, and the fire risk may mean more.
The number is not the whole answer
The calculator gives you a quantity from the floor area. A good fire plan also looks at the following:
- The type of fire risk: a kitchen, a paint store and an office all burn in different ways
- The type of extinguisher: using the wrong one can make a fire worse
- Travel distance: standards set a maximum walking distance to the nearest extinguisher, which is often in the range of 20 to 30 metres for general fires
- Special hazards: places with flammable liquids, gas, electrical rooms or cooking oil need extra or special extinguishers near them
- Layout: walls, partitions and stairs can make the real distance longer than it looks on a plan
Treat the calculator result as a minimum. Have a competent person confirm the final plan against the standard and the local fire authority’s rules that apply to you.
Fire classes in simple words
Fires are grouped into classes by what is burning. The letters differ a little between countries, so check the system your standard uses.
- Class A: ordinary solids such as wood, paper, cloth and plastics
- Class B: flammable liquids such as petrol, oil and paint
- Class C: flammable gases in the UK and Europe. In the US, Class C means electrical equipment.
- Class D: burning metals
- Class F or K: cooking oils and fats
- Electrical: fires in live electrical equipment, which need an extinguisher that does not conduct electricity
Which extinguisher for which fire?
- Water: for ordinary solids. Never use on live electrical equipment or on burning oil.
- Foam: for ordinary solids and flammable liquids.
- Dry powder: works on several types, including solids, liquids and gases, but it makes a mess and can reduce visibility in a small room.
- Carbon dioxide (CO2): good for electrical fires and flammable liquids, with no residue. It works best in small spaces.
- Wet chemical: made for cooking oil and fat fires in kitchens.
Most extinguishers have a colour band or label showing their type. Make sure that workers know what each one is for before there is a fire.
Where to put extinguishers
- Near exits and escape routes, so people can leave if the attempt fails
- Along the usual walking routes, not hidden in corners
- Close to the hazard, but not so close that a fire would block them
- Mounted on a wall or stand, with the handle about 1 metre above the floor for lighter units
- With a clear sign, and a clear space in front
- In the same place on every floor, so people find them without thinking
Keep them working
An extinguisher that does not work is worse than none, because people trust it. Do a regular visual check to make sure that the pin and seal are in place, the gauge is in the green, the hose is clear and the unit is not damaged. A competent person should service every extinguisher at least once a year, and record the date. Replace or refill any unit that has been used, even if it was only used a little.
Train people to use them
Many people have never held an extinguisher. Show them the basic steps, often remembered as PASS: pull the pin, aim at the base of the fire, squeeze the handle and sweep from side to side. Also teach them when not to fight a fire. If the fire is bigger than a small waste bin, if smoke is thick, or if the way out is at risk, leave, raise the alarm and call the fire service.
Step by step
- Measure the floor area of each floor.
- Enter the area and the number of floors in the calculator.
- Note the minimum number of extinguishers.
- Look at the fire risks in each area and choose the right types.
- Check the travel distances on your floor plan.
- Add extra units for special hazards.
- Have a competent person confirm the plan, then set up a check and service schedule.
Common mistakes
- Putting all extinguishers of the same type everywhere
- Counting extinguishers that are empty, blocked or out of date
- Using the floor area rule and forgetting travel distance
- Putting extinguishers in locked rooms
- Skipping training, so people panic or use the wrong one
- Forgetting extra cover for kitchens, workshops and electrical rooms
Linking it to your wider plan
Fire is a hazard that should be on your risk assessment. Score it with the risk matrix calculator, and then see how much the risk drops with the residual risk calculator. Extinguishers are only one part of fire safety. People also have to get out quickly, and the fire evacuation time calculator helps you check that. Add checks of your extinguishers to your safety audit.
Frequently asked questions
How many fire extinguishers are needed per square metre?
A common guideline is 1 extinguisher for every 200 square metres, with at least 2 on every floor.
Can I use one type of extinguisher for everything?
Some types, such as dry powder, work on many fires, but they are not the best choice everywhere. Choose by the fire risk of each area.
How often should extinguishers be checked?
Do a quick visual check regularly, and have a competent person service them at least once a year.
Do I need extinguishers if I have sprinklers?
Usually yes. Sprinklers and extinguishers do different jobs. Check your local rules and the advice of a competent person.
Is this result a legal requirement?
No. It is a guideline. Your local fire authority, insurer and standard make the final decision.
Learn this properly
Fire safety and extinguisher selection are covered in NEBOSH, IOSH and OSHA courses. ISH Institutes teaches these in Peshawar. Chat with us on WhatsApp and we will help you pick the right course.