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HVAC dampers explained: volume, fire and smoke dampers

Updated 23 October 2026 · SEO Dons Editorial

What do the different types of damper do?

Dampers are mechanical devices that regulate or stop airflow. Systemair, a ventilation manufacturer, describes them as devices that open, close or part-close to vary how much air passes along a duct. In commercial buildings they split into dampers that manage airflow and dampers that protect the building from fire and smoke.

DamperWhat it doesWhat the sources say
Manual volume controlSets airflow by opening, closing or partly closing a bladeSystemair: used to regulate airflow in commercial and industrial ventilation
Motorised control or shut-offAdjusts or closes airflow on a signalSystemair's TUNE-R is a control and shut-off damper in manual or motorised versions with a position indicator
Backdraught (non-return)Stops air entering the building through a duct when the fan is offSystemair's VKM shutter stays open while powered and closes automatically when the supply is removed
Fire damper (FD)Closes on heat to hold a compartment lineBESA: fusible link, typically around 72 degrees C; classified E (integrity) only
Motorised fire damper (MFD)Closes on a signal, with smoke leakage performance addedBESA: typically classified ES or EIS
Smoke control damper (SCD)Opens or closes as part of a smoke control systemBESA: always motorised, with no fusible link

Terms vary. Approved Document B talks of fire dampers and fire and smoke dampers, while BESA's DW 145 guidance says motorised fire dampers are frequently, though incorrectly, called fire and smoke dampers, and that smoke control dampers must not be substituted with motorised fire dampers. Check which product a specification means before comparing quotes.

How are volume control dampers set?

They are set during commissioning, when the airflow to each branch is adjusted to the design figure. CIBSE's Commissioning Code A sets out how ventilation and ductwork systems are set to work, functionally tested and regulated. Ask for the measured airflows and damper positions in the handover record, and see the commissioning and handover guide for what the pack should hold.

Where does Building Regulations guidance call for fire dampers?

Approved Document B Volume 2, the fire safety guidance for England, says that where air handling ducts pass through fire-separating elements, the fire performance of those elements should be preserved using one or more of four methods: thermally activated fire dampers, fire resisting enclosures, protection using fire resisting ductwork, and automatically activated fire and smoke dampers triggered by smoke detectors. In most ductwork systems, it says, a combination is best.

  • Escape routes: it asks for a fire and smoke damper at each point where ductwork enters or leaves a section of protected escape route, worked by a smoke detector or other suitable detection. It rules out the thermally activated method for extract ductwork passing through those enclosures, because heat-activated devices may not be triggered by large volumes of smoke passing them.
  • Kitchens: the thermal and smoke-detector-triggered methods are ruled out for kitchen extract, because grease build-up in the duct can affect dampers. The kitchen extraction guide covers kitchen extract ductwork.
  • Installation: dampers should be sited within the thickness of the fire-separating element, securely fixed and provided with access for inspection, testing and maintenance.
  • Rating: they should conform to BS EN 15650 and carry at least an E classification of 60 minutes, or the integrity rating of the surrounding fire-resisting element if that is higher.
  • Sleeping risk: dampers should be actuated by both smoke detector-controlled automatic release and thermally actuated devices, with exceptions the document sets out.

BSI describes BS EN 15650 as covering fire dampers used with fire separating elements to keep fire compartments intact. BESA adds that a damper is tested as part of an assembly: the duct, the damper, the wall or floor around it and the penetration seal.

What must be inspected and tested, and who is responsible?

The Regulatory Reform (Fire Safety) Order 2005 extends to England and Wales only. Article 17 requires the responsible person to keep the premises, and the facilities, equipment and devices provided, on a suitable maintenance system and in efficient working order and good repair. BESA reads the Order as expecting fire risk assessments to cover dampers and other passive fire protection.

Article 17 sets no test interval. BSI describes BS 9999 as giving recommendations and guidance, and BESA reports BS 9999:2017 as requiring a competent person to test every fire damper once installed and then at least once a year. BESA adds that motorised dampers are tested at least annually too, and that dust-laden or heavily polluted settings need more frequent testing, with commercial kitchen extract as an example.

BESA's DW 145 guidance defines four inspection types:

  • Type 1: pre-handover inspection of new dampers, or a first inspection where none was done.
  • Type 2: about a year after completion of new-build or refurbishment, where a Type 1 report exists.
  • Type 3: existing buildings with little or no documentation, to set the baseline.
  • Type 4: routine functional tests once a Type 2 or Type 3 report exists.

Inspectors must show appropriate skills, knowledge, experience and behaviour. Responsibility follows article 3: for a workplace it is the employer, where the workplace is at least partly under their control, and otherwise the person in control of the premises for a trade, business or other undertaking, or the owner where that person is not in business. Article 17 also allows arrangements with the occupier of other premises in the same building, so in a let building settle in writing who tests shared dampers.

What records should a facilities manager keep?

BESA says every inspection must produce a written report on each damper tested. A useful record holds:

  • an asset number and location reference for each damper;
  • its classification, size and manufacturer;
  • the test date and inspector identification;
  • the pass or fail result, with any non-compliance and recommended corrective actions and timescales;
  • dated photographs linked to the asset number;
  • the Declaration of Performance documents, which BESA says must be held for all fire dampers.

BESA says that for higher-risk buildings the golden thread must hold the dampers' installation specifications, test history, maintenance schedules and inspection reports.

What commonly goes wrong with fire dampers?

BESA lists incomplete or damaged penetration seals among the failures it finds most often, and says obstructions that stop a damper closing fully turn up frequently in functional tests. Its examples include dust and debris on the blades and ductwork insulation protruding into the frames. Fusible links need to be present and correctly rated, and BESA says a damper nobody can reach cannot be tested or maintained to the required standard, which is why access panels belong in the design.

The DW/144 guide covers how ductwork is built and tested, and the spiral, rectangular or flexible ductwork guide compares the duct types the dampers sit in. For the systems around them, see commercial ventilation and MVHR. You can send an enquiry through the form on this site.

Sources

Common questions

How often must fire dampers be tested?

Article 17 of the Fire Safety Order requires a suitable system of maintenance but sets no interval. BESA reports BS 9999:2017 as requiring a competent person to test every fire damper once installed and then at least once a year, with more frequent testing in dust-laden or polluted settings. BS 9999 is a code of practice, so a fire risk assessment and any insurer may set a tighter interval.

Are fire dampers and smoke dampers the same thing?

No. BESA's DW 145 guidance separates fire dampers, motorised fire dampers and smoke control dampers. Smoke control dampers are always motorised, have no fusible link and must not be substituted with motorised fire dampers.

Can a fire damper be used on kitchen extract ductwork?

Approved Document B Volume 2 rules out the thermally activated and smoke-detector-triggered methods for kitchen extract, because grease build-up inside the duct can affect dampers. That leaves the fire resisting enclosure and fire resisting ductwork methods.

Who is responsible for fire dampers in a let building?

Under article 3 of the Fire Safety Order the responsible person is the employer where a workplace is at least partly under their control, otherwise the person in control of the premises for a business, or the owner where that person is not in business. Article 17 allows arrangements with the occupier of other premises in the same building, so agree in writing who tests shared dampers.

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