Fire Damper Calculator

Fire dampers are required wherever a duct penetrates a fire-separating element (compartment wall or floor) to maintain the fire resistance of that element. This is required by Approved Document B and BS 9999. Without a damper, fire and smoke can spread through the ductwork system.

Fire dampers must be tested by a competent person on completion of installation and at least once a year thereafter, under BS 9999:2017 and BESA DW145 (2024), with the responsible person keeping them in efficient working order under the Regulatory Reform (Fire Safety) Order 2005. The test (drop test) confirms the damper closes fully and resets correctly. Records must be kept. In dust-laden or polluted environments, and for motorised dampers tied into a BMS, more frequent testing may be needed.

As a rule, you need one fire damper at each point where a duct penetrates a fire-separating element — every compartment wall, compartment floor, cavity barrier or the enclosure to a protected escape route or place of special fire hazard (Approved Document B). The damper must be tested to BS EN 1366-2 and classified to BS EN 13501-3 for an integrity (E) rating that equals or exceeds the fire resistance of the element it penetrates: a 60-minute (EI 60) wall needs an E 60 damper, a 120-minute (EI 120) floor needs E 120, and so on. Integrity (E) is the mandatory damper classification in the UK; insulation (I) is only added where the fire strategy demands it, and an ES (integrity plus smoke leakage) damper is used on protected escape routes. This calculator does not count penetrations for you — you enter the quantity and fire rating, and it estimates the cost.

Fire dampers close when they detect heat (via fusible link or intumescent material) to prevent fire spread. Smoke dampers close when they detect smoke (via detector signal) to prevent smoke spread. Combined smoke/fire dampers provide both functions and are needed where smoke control is critical.

Yes. Every fire damper must be reachable so it can be inspected, tested and reset. BESA DW145 (2024) requires quick-release, insulated, sealed access panels built to DW144 and positioned adjacent to the damper. There is no single mandated panel size — it must be large enough for safe hand access to that particular damper; around 300mm square is a common practical minimum, but the required size depends on the damper.

As an indicative ex-VAT guide (2026): basic mechanical fire dampers cost roughly £80-£150 supply, motorised dampers with actuators £250-£450, and combined smoke/fire dampers £300-£500+. Installation adds about £80-£200 per damper and annual testing roughly £25-£45 per damper. These are estimates only — supply, install and test pricing is bespoke per site, duct size and quote, with no national tariff. Always get a written quotation.