Dampers
Ventilation dampers for airflow control, balancing, isolation and fire protection. Alpha Air supplies the full spectrum — from simple blast gate dampers for dust extraction branches to motorised fire and smoke dampers manufactured to your exact size — with circular sizes from 63mm and rectangular dampers made to order. We are a Leicester-based UK supplier: stocked dampers ordered by 3pm are despatched next day, and made-to-order dampers show their lead time on the product page.
Dampers for balancing and volume control
- Single blade dampers — a simple hand-adjusted blade for trimming airflow in round duct.
- Multi leaf volume control dampers — circular VCDs from 100mm to 630mm for accurate balancing of larger ducts, plus rectangular volume control dampers made to your width and height with hand control, extended spindle or 24V/230V actuator options.
- Opposed blade dampers — even airflow distribution, typically fitted behind grilles.
- Blast gate dampers — slide-gate shut-off for dust and fume extraction systems, in 13 diameters from 63mm to 355mm.
Backdraught and gravity control
Non return dampers stop air flowing backwards through a duct when the fan is off, and gravity shutters do the same job on the discharge side of wall-mounted fans, opening with airflow and closing under their own weight.
Fire dampers and fire & smoke dampers
Where ductwork passes through fire compartment walls and floors, building regulations demand protection. Our fire dampers are curtain-type units made to your duct size in galvanised or stainless steel. For systems that must also stop cold smoke, fire & smoke dampers add a thermally-triggered motorised blade with 24V or 230V actuator options, available in rectangular made-to-measure sizes and circular diameters. Type your width and height into the product page and the price calculates instantly — no quote round-trip needed.
Choosing the right damper
As a rule of thumb: balancing a branch calls for a single blade or multi leaf VCD; isolating extraction drops calls for a blast gate; preventing reverse flow calls for a non return damper or gravity shutter; and any duct penetrating a fire compartment needs a fire or fire & smoke damper. Sizes run from 63mm circular dampers right up to large made-to-order rectangular units, so one supplier covers the whole schedule. When ordering made-to-measure dampers, measure the duct opening rather than any existing damper’s flange, and choose the connection style — flanged or spigotted — to match your ductwork. If you are unsure, our team will happily talk it through before you order. Stocked circular dampers pair directly with our spiral ducting range, sharing the same standard diameters. UK mainland delivery is free on orders over £400 ex VAT, and every made-to-order damper shows its manufacturing lead time on the product page.
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Blast Gate Damper
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Fire/Smoke Dampers
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Multi Leaf Volume Control Damper
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Non Return Damper
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Single Blade Damper
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Fire Dampers
What Are Dampers?
Dampers are mechanical devices installed within ductwork to control, restrict, or shut off airflow. They serve three main purposes in ventilation systems: fire safety (preventing the spread of fire and smoke through ductwork), airflow regulation (balancing air distribution across zones), and backflow prevention (stopping reverse airflow when a fan is off).
Types of Dampers
Fire Dampers
Fire dampers are passive fire protection devices installed where ductwork penetrates a fire-rated barrier (wall, floor, or ceiling). They contain a fusible link that melts at a set temperature (typically 72°C), causing the damper blade to close automatically and seal the duct opening. This prevents fire and hot gases from spreading through the ductwork to other compartments.
UK Building Regulations (Approved Document B) and BS 9999 require fire dampers wherever ductwork passes through a fire compartment wall or floor. All our fire dampers are tested and certified to BS EN 15650 and carry CE marking.
Volume Control Dampers
Volume control dampers (also called balancing dampers or regulation dampers) are manually adjustable dampers used to balance airflow across different branches of a duct system. By partially closing dampers on branches with excess airflow, the system can be balanced so every outlet delivers the correct volume of air. Available in single-blade and multi-blade configurations for circular and rectangular ducts.
Non-Return (Backdraught) Dampers
Non-return dampers allow air to flow in one direction only, preventing reverse airflow when a fan is switched off. They are essential on extract systems to stop cold outside air being drawn back through the ductwork when the fan is not running. Available as gravity-operated butterfly or flap types.
Fire Damper Regulations
In the UK, fire dampers must be:
- Installed wherever ductwork penetrates a fire compartment wall or floor
- Accessible for inspection and testing (via access panels)
- Tested annually in accordance with BS 9999 and the Regulatory Reform (Fire Safety) Order 2005
- Installed by competent persons in accordance with the manufacturer’s instructions
Failure to install or maintain fire dampers is a serious breach of fire safety regulations. Building Control and the Fire Service can issue enforcement notices for non-compliance.
Why Choose Alpha Air?
We stock a comprehensive range of circular and rectangular fire dampers, volume control dampers, and non-return dampers from BSB and other certified manufacturers. Our team can advise on the correct specification for your project. Call 0116 246 0031 for expert guidance.
Frequently Asked Questions
Where do I need to install fire dampers?
Fire dampers must be installed wherever ductwork passes through a fire-rated wall, floor, or ceiling (a fire compartment boundary). This is a legal requirement under UK Building Regulations Approved Document B. The damper maintains the fire rating of the barrier by automatically closing when it detects heat.
How often do fire dampers need to be tested?
Fire dampers should be tested annually in accordance with BS 9999. Testing involves visually inspecting the damper, checking the fusible link, operating the blade mechanism, and verifying it closes and resets correctly. Records of all tests must be kept as part of the building’s fire safety documentation.
What is a fusible link in a fire damper?
A fusible link is a heat-sensitive mechanical device that holds the fire damper blade open during normal operation. When the temperature reaches a set point (typically 72°C), the link melts or releases, allowing the blade to close under spring pressure. The fusible link is a consumable part and must be replaced after activation.
What is the difference between a fire damper and a smoke damper?
A fire damper closes when it detects heat (via a fusible link) to prevent fire spreading through ductwork. A smoke damper closes when it receives a signal from the building’s fire alarm or smoke detection system to prevent smoke spreading. Some installations require combination fire/smoke dampers that respond to both heat and alarm signals.