BS 5306-8: how many extinguishers a UK premises needs, and where

Quick answer. BS 5306-8 sets the rules for choosing and positioning portable extinguishers in UK premises. The baseline for Class A (ordinary combustibles) risk: at least two extinguishers per floor with a combined rating of at least 26A for the first 105 square metres of floor area, plus proportional cover above that, and no person should travel more than 30 metres to reach one. Specific risks (electrical, flammable liquid, cooking oil) require additional class-appropriate extinguishers sited within 10 metres of the hazard.

BS 5306-1 covers installing extinguishers, BS 5306-3 covers maintaining them, and BS 5306-8 answers the question that comes before both: how many extinguishers does this premises actually need, of which types, and where do they go. It is the standard a fire risk assessor works from when they flag your extinguisher provision as inadequate, and the one to read before buying units.

The Class A baseline calculation

Class A covers ordinary combustibles: paper, wood, textiles, most furnishings. Almost every UK workplace carries Class A risk, so BS 5306-8 makes it the baseline calculation:

• Minimum two extinguishers per storey (a single extinguisher leaves no cover while it is being serviced or after a discharge).
• Combined minimum rating of 26A per 105 square metres, calculated as 0.065 x floor area in square metres, rounded up to the next available rating.
• A typical 13A-rated extinguisher (9 litre water or 6 litre foam) means two units cover the first 105 square metres.

Worked example: a 400 square metre open-plan office floor needs a combined rating of 0.065 x 400 = 26A. Two 13A units meet the number, and the travel distance rule below decides whether two are actually enough for the layout.

The 30-metre travel distance rule

No person should have to travel more than 30 metres from any point on the floor to the nearest Class A extinguisher. On long or irregular floors this rule, not the area calculation, usually determines the count. A warehouse aisle 90 metres long needs extinguishers roughly every 60 metres along it regardless of the modest rating requirement its floor area produces.

For specific risks the distances tighten:

• Class B (flammable liquids): within 10 metres of the hazard.
• Class F (cooking oils and fats): within 10 metres of the cooking appliance, wet chemical type.
• Electrical risk: a CO2 unit within 10 metres of significant electrical equipment (server rooms, switch rooms, plant).

Matching extinguisher class to the risk

BS 5306-8 expects the extinguisher mix to follow the fire risk assessment, not a one-size default:

• Water or foam (Class A): the workhorse for offices, corridors, education, retail floors.
• Foam (Class A and B): where flammable liquids are stored or used alongside ordinary combustibles.
• CO2 (electrical, Class B): server rooms, comms cabinets, switch rooms, workshops with powered equipment. Almost always paired with a Class A unit nearby because CO2 has minimal effect on ordinary combustibles.
• Wet chemical (Class F): commercial kitchens with deep fat fryers. A fire blanket supplements but does not replace it.
• Powder (multi-class): effective outdoors and on vehicles but discouraged indoors by BS 5306-8 guidance because discharge in enclosed spaces destroys visibility and harms breathing; many assessors now flag indoor powder units for replacement.

Siting rules assessors actually check

• On escape routes and at exits, so a person moving toward safety passes cover, never deeper into the building to fetch it.
• Mounted at the BS 5306-8 handle height: roughly 1 metre for heavier units, up to 1.5 metres for smaller ones, never on the floor unless in a stand.
• Visible and signed. Where an extinguisher is not directly visible (recesses, columns), a sign to BS ISO 7010 above it.
• Consistent locations floor to floor. Repeat visitors and staff find extinguishers where they expect them; assessors treat inconsistent siting as a finding.
• Clear of obstruction. Stock, bins, and furniture creep in front of extinguishers between audits; the monthly BS 5306-3 visual check exists partly to catch exactly this.

Common findings on UK premises

The recurring extinguisher-provision findings in fire risk assessments:

1. Single extinguisher on a floor. Breaches the minimum-two baseline.
2. Powder units indoors in offices and stairwells, flagged for phased replacement with water/foam plus CO2.
3. Travel distance breaches on reconfigured floors: the layout changed, the extinguisher positions did not.
4. Missing Class F cover in kitchens that gained a fryer after the original provision was designed.
5. No provision review after refit. BS 5306-8 expects provision to be reassessed whenever use or layout changes materially.

Every one of these is cheap to fix and expensive to have on the record unfixed when an incident happens.

Keeping the provision compliant over time

The initial BS 5306-8 design decays as premises change. Three habits keep it current:

• Re-check provision at every fire risk assessment review, not just at installation.
• Log every extinguisher as an asset with type, rating, and position, so a floor reconfiguration triggers a provision check rather than a surprise at the next assessment.
• Tie the monthly visual to the position, not just the unit. The BS 5306-3 monthly check should confirm the extinguisher is present at its designated location, visible, and unobstructed, which is a positioning check as much as a condition check.

The fire extinguisher inspection checklist covers the monthly and annual cycle in detail, and the fire safety solution page shows how Hovermarks tracks each extinguisher as a tagged asset with its siting, rating, and inspection history in one record.