Fire Dampers

Fire dampers prevent fire and smoke spreading through ventilation ductwork between fire compartments. Required by Building Regulations wherever a duct penetrates a fire-rated wall, floor, or compartment boundary. We stock the full range: BSB circular single-blade fire dampers (FD-C series, externally resettable), Systemair PKI in-duct circular fire dampers, circular intumescent fire blocks from 100mm to 200mm, square intumescent fire blocks from 150mm to 600mm, and air valves with integral fire dampers for MVHR and MEV supply/extract terminals. All products are tested and certified to BS EN 15650. Next-day delivery, trade pricing.

Circular Intumescent Fire Blocks / Square Intumescent Fire Blocks / Air Valves With Fire Damper / Non-Return Dampers

Where are fire dampers required?

Wherever ductwork passes through a fire compartment boundary — that means fire-rated walls, floors, and partitions. Approved Document B of the Building Regulations requires that penetrations through fire-separating elements are protected to maintain the compartment's fire resistance. In practice, this covers ductwork in offices, schools, hospitals, care homes, hotels, and residential blocks of flats. If you're running a duct through any wall or floor that has a fire rating (typically 30, 60, 90, or 120 minutes), you need a fire damper at that penetration. The damper's fire rating must match or exceed the rating of the element it passes through.

What's the difference between a fire damper and an intumescent fire block?

A mechanical fire damper (like the BSB FD-C or Systemair PKI) has a moving blade that closes when the thermal fuse releases — it can be reset and tested after activation. They're used in active ventilation ductwork where airflow is continuous during normal operation. An intumescent fire block has no moving parts — it's a collar or sleeve containing intumescent material that expands in a fire, crushing and sealing the duct penetration. Intumescent blocks are typically used on passive ventilation openings (air transfer grilles between rooms), extract terminals, and smaller duct penetrations. They're simpler and cheaper but can't be reset — once activated, they're replaced.

How often do fire dampers need testing?

BS 9999 recommends annual inspection and testing of all fire dampers. This involves a visual check of the damper and its access panel, followed by a drop test — releasing the blade to confirm it closes fully, then resetting it. Some insurers and local authorities require six-monthly testing in higher-risk buildings like hospitals and care homes. Every test must be recorded with the date, damper location, result, and the name of the person who carried out the inspection. If a damper fails its drop test, it must be repaired or replaced immediately — a stuck-open fire damper is a serious fire safety breach.

Do I need an access panel for each fire damper?

Yes — Building Regulations and BS 9999 both require that every fire damper is accessible for inspection and testing. In practice, this means fitting a duct access door or building in a ceiling access panel directly adjacent to each damper. A fire damper that can't be reached for its annual drop test is non-compliant. This is one of the most common issues found during fire risk assessments — dampers installed above fixed ceilings with no access. Plan the access at design stage, not as an afterthought. The access panel must be large enough to see the damper blade, operate the test release, and reset the mechanism.

What size fire damper do I need?

The fire damper must match the duct size at the point of penetration. For circular ductwork, specify the damper by the duct's internal diameter — 100mm, 125mm, 150mm, 200mm, 250mm, etc. The BSB FD-C range and Systemair PKI range both cover standard circular sizes. For rectangular ductwork, multi-blade fire dampers are sized to match the duct cross-section. For passive air transfer openings not connected to ductwork, use intumescent fire blocks — circular blocks for round openings, square blocks for rectangular openings. Always match the fire rating of the damper to the fire rating of the wall or floor it's installed in — a 60-minute wall needs at least a 60-minute damper.

Can I use intumescent fire blocks on MVHR systems?

Yes, intumescent fire blocks are commonly used on the individual room supply and extract terminals of MVHR and MEV systems. The air valve with integral fire damper we stock combines a standard adjustable air valve with an intumescent collar built into the back. This means you get airflow control and fire protection in one unit, without needing a separate mechanical fire damper at every room terminal. They're particularly useful in residential blocks of flats where each flat's ventilation terminals penetrate the fire compartment between the flat and the communal riser or ceiling void. Building Control will typically accept these for up to 60-minute fire-rated separations.