Key Takeaways
- BSB are one of the UK's most trusted fire damper manufacturers, with over 60 years of experience and an active role in UK standards development
- The BSB FD-C is a circular single blade damper — externally resettable, E120 rated, and available in galvanised and stainless steel
- All tested installation variants achieve E120 classification — the highest fire resistance rating under EN 1366-2
- An optional microswitch provides remote position indication for integration with a BMS or fire alarm panel
- BSB fire dampers are compliant with BS EN 15650 and meet UK Building Regulations Approved Document B requirements
If you've been specifying or installing fire dampers in UK commercial or residential buildings, you'll know the BSB name. With over 60 years of manufacturing experience and a reputation built on consistent test data and straightforward compliance, BSB fire dampers are one of the most widely specified brands in the UK. This guide covers the BSB FD-C Series in detail — what it is, how it's specified, and when to use it. You can browse and order the full range at our BSB fire dampers page.
What Is the BSB FD-C Series?
The BSB FD-C is a circular single blade fire and volume control damper — the standard specification mechanical fire damper for round ductwork penetrating fire-resisting walls, floors, and partitions in UK buildings.
Key specifications:
- Design: Circular single blade, spring-loaded closure on thermal fuse activation (~72°C)
- Operation: Externally resettable — the blade returns to the open position without removing the damper from the duct or the wall
- Materials: Galvanised steel (standard) and stainless steel (for humid or corrosive environments)
- Fire classification: E120 — tested to EN 1366-2, achieving the highest available fire resistance rating
- Standard compliance: BS EN 15650 — meets all UK and European fire damper performance requirements
- Optional microswitch: Provides remote electrical indication of open/closed blade position
- Tested installation variants: Dry walls, masonry walls, and concrete floors — all achieving E120
E120 Fire Classification Explained
E120 is the highest fire resistance classification for fire dampers under EN 1366-2. The "E" refers to integrity — the ability to prevent fire and hot gases from passing through the damper — and "120" means this has been proven for a minimum of 120 minutes in standardised fire testing.
In practice, an E120-rated damper is suitable for installation in both 60-minute and 120-minute fire-rated compartments — the most common fire resistance periods specified in UK commercial buildings. Having a single product that covers both ratings simplifies specification and procurement.
BS EN 15650 Compliance
BS EN 15650 is the European standard for fire dampers in ventilation systems — covering performance, testing, and CE marking requirements. All BSB FD-C dampers are manufactured and tested to this standard. This means full test certificates and installation data are available to support specification submissions and building control sign-off — something that's increasingly required on commercial projects where passive fire protection documentation is scrutinised closely.
Galvanised or Stainless Steel?
For most installations — commercial offices, schools, hospitals, residential blocks — galvanised steel is the standard and correct choice. It's corrosion-resistant under normal conditions, cost-effective, and the material the FD-C has been tested and rated in.
Stainless steel variants are specified for environments where the damper is exposed to persistent moisture, high humidity, or chemical corrosives — commercial kitchens, food production facilities, swimming pool plant rooms, and pharmaceutical environments are the most common examples. Both variants carry the same E120 classification and BS EN 15650 compliance.
The Microswitch Option
The optional microswitch provides a remote electrical signal indicating whether the damper blade is in the open or closed position. In buildings where fire damper status needs to be monitored centrally — typically via a building management system (BMS) or fire alarm panel — the microswitch allows this without requiring physical access to each damper.
This is particularly relevant on larger commercial projects where the total number of fire dampers makes manual status checks impractical, and where the responsible person under the Regulatory Reform (Fire Safety) Order 2005 needs a reliable means of confirming damper status after a fire event or test.
Why BSB?
BSB don't just manufacture to the current standards — they actively participate in their development. As changes to UK and European fire protection standards are proposed and progressed, BSB provide input and pass relevant updates directly to designers, building control authorities, and installers. For specifiers, this means the product documentation and test data you receive reflects the current regulatory position, not just historical test work.
Their factory operates a build-to-order flow process, meaning lead times are short for a product manufactured to specification. For projects where fire damper documentation is required for sign-off, BSB's test certificates and installation data are well-organised and available on request.
Browse our full BSB fire dampers range at eFans, or see the broader fire dampers collection including intumescent fire blocks and fire-rated air valves.
Frequently Asked Questions
What is the BSB FD-C and how does it work?
The BSB FD-C is a circular single blade fire damper designed for installation in round ductwork where it penetrates a fire-resisting wall, floor, or partition. During normal operation the blade is held open. In a fire, the thermal fuse — rated at approximately 72°C — melts, releasing the spring-loaded blade which closes automatically to seal the duct and maintain fire compartmentation. It's externally resettable, meaning the blade can be reset to the open position from outside the duct without removing the damper or dismantling the installation.
What does the BSB FD-C fire classification mean in practice?
All tested installation variants of the BSB FD-C achieve E120 — the highest fire resistance classification for dampers under EN 1366-2. In practice this means the damper has been tested and proven to prevent fire and hot gases from passing through it for a minimum of 120 minutes. This makes it suitable for both 60-minute and 120-minute fire-rated compartments — the two most common specifications in UK commercial and residential buildings.
Are BSB fire dampers the same as smoke dampers?
No — the BSB FD-C Series is a fire and volume control damper, not a smoke damper. BSB fire dampers close in response to heat (the thermal fuse at ~72°C), stopping the spread of flames and hot gases. A smoke damper is triggered by a smoke detection signal, independently of temperature, and is designed to prevent smoke movement through the ductwork at an early stage of a fire. Some installations require combination fire and smoke dampers — if you need smoke control capability, contact us at hello@efans.co.uk and we'll advise on the right product.
What is a single blade fire damper?
A single blade (or single leaf) fire damper has one blade that pivots across the duct opening to close it. This is the standard configuration for circular ductwork applications — the blade diameter matches the duct bore and, when closed, seals the duct cross-section fully. The BSB FD-C uses this design. Multi-blade dampers are used in rectangular ductwork where a single blade would be impractically large. For round duct penetrations, single blade dampers like the FD-C are the correct and most commonly specified type.
Can BSB fire dampers be installed in ductwork fire penetrations?
Yes — BSB FD-C dampers are specifically designed for duct fire penetrations. They are tested and certified for installation in the most common UK construction types: dry (plasterboard) walls, masonry walls, and concrete floors. Each installation type has its own test certificate and installation detail. This breadth of tested variants means the FD-C can be specified across a wide range of building types and construction methods without needing a different product for each application.
How often do BSB fire dampers need to be tested and maintained?
UK guidance under BS 9999 and the Regulatory Reform (Fire Safety) Order 2005 requires fire dampers to be drop-tested at least annually — and more frequently in high-risk environments. Each test must be recorded in the building's fire safety log. Dampers that fail to close fully must be repaired or replaced. The externally resettable design of the BSB FD-C makes annual testing more straightforward than older designs that require duct access to reset.