What Is A Fire Damper And Its Role In HVAC Fire Compliance

Fire Damper Definition And Purpose

A fire damper is a critical component of any HVAC system where ductwork passes through fire-resisting compartment walls or floors. Its primary function is to preserve compartmentation in the event of a fire by automatically closing upon detection of elevated temperatures, preventing the spread of flame and, in some cases, smoke.

As defined in DW 145: A Guide to Good Practice for the Installation and Maintenance of Fire Dampers, a fire damper is:

"A device for use in heating, ventilation and air-conditioning (HVAC) systems at fire boundaries to maintain compartmentation and protect means of escape in case of fire. A fire damper should close and remain closed to maintain compartmentation. It has a fusible link or thermal element to help ensure this."

Fire dampers are typically installed at the point where ventilation ducts penetrate fire compartment lines, either walls (vertical orientation) or floors (horizontal orientation). In a compliant system, the fire damper closes securely in response to heat, often using a fusible link or thermal element that releases once a specific temperature threshold is reached. Some dampers are motorised and respond to signals from a fire alarm or building management system (BMS).

Why They Matter

Fire dampers are not optional. Their inclusion is often required by UK Building Regulations and fire safety legislation. They are fundamental to achieving:

• Passive fire protection by maintaining the fire resistance of compartment boundaries
• Protection of escape routes, ensuring safe egress during a fire event
• Compliance with Approved Document B, which mandates specific methods for fire-stopping ductwork passing through compartments

Improper specification or incorrect installation of fire dampers can compromise life safety systems. As BESA notes in the DW 145 foreword, inspections have revealed widespread non-compliance across the industry, with many dampers found installed incorrectly or not in accordance with manufacturer instructions.

Regulatory And Standards Basis

Fire dampers are tested and classified under a range of harmonised European standards, which have been adopted into UK law. These include:

• EN 15650 - Product standard
• EN 1366-2 - Fire resistance testing
• EN 13501-3 - Classification (e.g. E, EI, ES, EIS)
• BS EN 15882-2 - Extended field of application, where relevant

They are also covered under UK fire safety legislation, such as:

• The Building Regulations 2010 (Part B)
• The Building Safety Act 2022
• The Regulatory Reform (Fire Safety) Order 2005
• The Fire Safety Act 2021

The Role Of Fire Dampers In Compartmentation Strategy

In most modern buildings, ductwork crosses multiple fire compartments. Without an effective barrier, these ducts can act as channels for fire and smoke. Fire dampers provide the necessary isolation to ensure each compartment can contain fire for a specified duration, typically ranging from 30 to 120 minutes.

Designers must ensure dampers are tested for the wall or floor construction in which they are installed and that they are certified for the fire-resistance rating of the compartment in which they are installed. In turn, installers are expected to follow both DW 145 and the specific manufacturer's tested installation details. This includes the type and depth of penetration seals, the support arrangements, and the orientation of the damper.

How Fire Dampers Work In HVAC Systems

Fire dampers are designed to operate as a passive fire protection measure, automatically closing to prevent the passage of fire and, in some cases, smoke through ductwork where it penetrates compartment boundaries. They are triggered by heat or a fire alarm signal, depending on their type, and are essential for preserving the integrity of a building's fire strategy.

Integration With HVAC Systems

In a typical HVAC system, ductwork runs through multiple fire compartments, often embedded within walls, ceilings, or service risers. When this ductwork breaches a fire-resistant barrier, it presents a risk of allowing fire and smoke to travel between compartments. A fire damper is positioned at these penetration points to close when fire conditions are detected.

The fire damper remains open during normal operation to allow air to circulate freely through the ventilation system. Upon detection of fire, the damper activates and closes, restoring the fire resistance of the wall or floor through which the duct passes.

Activation Methods

The most common types of activation include:

• Thermal release mechanisms: These use fusible links or thermal elements that melt or fracture at a specific temperature, usually around 72°C, causing the damper blades to close under spring pressure.
• Motorised closure: Some dampers, especially those used in escape routes or sleeping accommodation, are motorised and connected to a fire alarm system. These are triggered automatically via a failsafe actuator when smoke or fire is detected.

Maintaining Compartmentation

The primary function of a fire damper is to maintain compartmentation. In the event of a fire, the damper must not only close but also remain closed, preventing the passage of flames and hot gases. When a motorised fire damper with an ES or EIS classification is used, it also helps to limit smoke leakage and, where applicable, insulates against heat transfer.

DW 145 clearly states that fire dampers are tested to perform as part of an assembly, which includes the duct, the damper itself, the surrounding wall or floor construction, and the penetration seal. This means that even if a damper closes correctly, failure of the seal or fixings can render the installation non-compliant or ineffective.

Control And Feedback

Some motorised fire dampers provide feedback to the building management system (BMS) to confirm their operational status. This can be essential in high-risk buildings, especially where dampers are used in smoke control zones, sleeping areas, or protected shafts. While fire dampers are generally passive in operation, their performance must be tested and verified during commissioning and regularly maintained to ensure reliability in a fire situation.

Fire Damper Types: FD, MFD, And SCD

Understanding the different types of fire dampers is essential for ensuring correct specification and installation. Each type serves a distinct purpose within a building's overall fire safety strategy and must be selected based on the location, building use, and space risk.

DW 145 classifies fire dampers primarily into three types:

• FD (Fire Damper)
• MFD (Motorised Fire Damper)
• SCD (Smoke Control Damper)

Each has different performance requirements, activation methods, and applications.

FD: Fire Damper (E Classification)

An FD, or standard fire damper, is the simplest form. It is typically a mechanical device fitted with a fusible link or thermal element that causes the damper to close when exposed to a predefined temperature, commonly 72°C. Once triggered, the blades close under spring pressure and remain closed, helping to preserve the fire compartment by preventing the passage of flame and hot gases.

Fire dampers of this type are classified with E (Integrity) only. This means they have been tested to maintain physical integrity for a specified period, usually 30, 60, or 120 minutes, depending on the classification.

FDs do not offer insulation or smoke leakage performance and should not be used where smoke control or protection of escape routes is required. DW 145 clearly states that FDs offer no smoke leakage capability, which is an important distinction when evaluating suitability.

MFD: Motorised Fire Damper (ES Or EIS Classification)

Motorised fire dampers, or MFDs, combine the fire-resisting function of a standard FD with additional smoke leakage and, optionally, insulation performance. They are typically classified as ES (Integrity and Smoke leakage) or EIS (Integrity, Insulation, and Smoke leakage).

MFDs are fitted with failsafe actuators which hold the damper open under normal operation. In the event of a fire, the actuator is de-energised by either a thermal element or a signal from the building's fire detection system. This triggers the damper to close, maintaining both the fire and smoke compartmentation.

MFDs are specifically required in high-risk areas such as:

• Escape routes
• Sleeping accommodation
• Phased evacuation of buildings
• Firefighting shafts
• Mobility-impaired refuge areas

They are frequently, though incorrectly, referred to in specifications as "fire and smoke dampers" or "motorised fire/smoke dampers" (MFSDs). DW 145 warns against this terminology, which can confuse. A motorised fire damper is not a smoke control damper.

SCD: Smoke Control Damper

Smoke control dampers are an entirely separate product type, governed by a different set of standards and purposes. These devices are installed within systems designed specifically to extract or contain smoke.

Unlike FDs and MFDs, SCDs are always motorised and feature open-close actuators without any thermal elements or fusible links. Their role is to either allow or restrict the passage of smoke through ducts as part of an active smoke control strategy.

Key standards for SCDs include:

• EN 12101-8 (Product standard)
• EN 1366-10 (Fire resistance testing)
• EN 13501-4 (Classification)

SCDs must not be substituted with MFDs. Doing so could compromise a building's smoke control strategy and violate compliance requirements. DW 145 highlights this as a recurring issue where incorrect product selection leads to non-compliance and increased risk to life safety.

Fire Damper Activation Methods And Mechanisms

Fire dampers rely on reliable activation mechanisms to ensure they respond correctly during a fire event. The method by which a damper activates is determined by its type, classification, and intended application. Understanding how different fire dampers operate is essential to correct specification, installation, and ongoing compliance with DW 145.

Fire dampers fall into two broad activation categories: thermally activated (mechanical) and electrically activated (motorised).

Thermally Activated Fire Dampers

Thermally activated dampers are usually installed in standard ventilation systems where basic integrity is required. These devices are triggered by a fusible link or thermal element that reacts to a rise in temperature.

• Fusible links are designed to melt at a predetermined temperature, typically around 72°C.
• Once the link melts or fractures, a spring mechanism is released, causing the damper blades to close rapidly.
• The damper remains closed throughout the fire event, helping to maintain compartmentation.

These dampers are mechanically simple and require no external power or wiring. They are most often classified as FD and carry an E classification only, meaning they provide integrity without insulation or smoke leakage protection.

Motorised Fire Dampers

Motorised fire dampers (MFDs) are more complex and are used in higher-risk areas, including protected escape routes, sleeping accommodation, and places of relative safety.

Unlike fusible link models, MFDs are held open by an electrically powered actuator. In the event of a fire, the damper receives a signal to close, and the actuator either drives the damper shut or allows it to shut, depending on the design.

Motorised dampers may activate by:

• Loss of power (failsafe close)
• Direct input from a fire alarm system
• Integration with a building management system (BMS)

These dampers typically include a thermal sensor or manual reset function, depending on their specification.

Where a reduced smoke leakage classification is required (ES or EIS), motorised dampers are essential. They must close promptly and completely in response to either heat or smoke signals and must remain closed to maintain both fire and smoke separation. DW 145 advises that dampers with these functions are not to be confused with smoke control dampers, which serve a different role entirely.

Summary of Activation Methods

Importance of Activation Reliability

DW 145 emphasises the importance of correct activation as a life safety feature. Faulty dampers that fail to close, close late, or remain partially open due to incorrect wiring, poor installation, or inappropriate selection can lead to:

• Breach of compartmentation
• Smoke migration into escape routes
• Potential regulatory non-compliance

For this reason, commissioning tests, regular inspections, and accurate documentation of activation performance are essential throughout the damper's lifecycle. Installers and commissioning teams must confirm not only mechanical movement, but also the reliability of the triggering mechanism under real-world conditions.

Fire Damper Classifications: E, EI, ES, And EIS Explained

Fire dampers are classified using a European system that defines their performance in a fire. This includes how long they can resist the passage of flames, limit the spread of smoke, and in some cases, reduce heat transfer. These characteristics are essential for maintaining compartmentation and supporting life safety systems.

The most common classifications include:

• E for Integrity
• EI for Integrity and Insulation
• ES for Integrity and Smoke Leakage
• EIS for Integrity, Insulation and Smoke Leakage

Each classification is accompanied by a fire resistance period in minutes. The classification may also specify the mounting orientation and the direction from which the fire exposure has been tested. These details are critical when matching a fire damper to its intended location, particularly where the system protects escape routes, sleeping accommodation or phased evacuation zones.

DW 145 sets out how these classifications are defined and provides guidance on where each is appropriate. The document includes detailed instructions on how to select the correct classification based on factors such as:

• The type of compartment and its required fire resistance
• The damper's orientation and supporting construction
• The building's fire strategy and associated space risk

Correct classification is not simply a technical specification. It is a compliance requirement under UK Building Regulations. Using the wrong classification can result in non-compliance and may lead to enforcement action or costly remedial work.

Fire Compartmentation And Why Fire Dampers Matter

Fire compartmentation is a fundamental principle of passive fire protection. It involves dividing a building into discrete fire-resisting units designed to contain fire and smoke for a defined period. This prevents the spread of fire from one area to another, protecting escape routes, limiting structural damage, and supporting firefighting operations.

When ventilation ductwork passes through these compartment boundaries, it creates a potential breach in the wall or floor's fire resistance. In the event of a fire, ducts can act as unintentional conduits for flame, heat, and smoke. Fire dampers are used at these penetration points to restore the compartment line and maintain its performance for the required fire resistance period.

DW 145 defines the fire damper as a device that closes automatically upon detection of heat and remains closed, helping to protect adjacent compartments. It highlights the importance of selecting and installing dampers that are tested for the specific wall or floor construction in which they are to be used.

A compliant fire damper installation must ensure the following:

• The damper has been tested and classified for the correct fire resistance period.
• The supporting construction and sealing method match the tested assembly.
• The damper closes fully and reliably under fire conditions.
• Access is provided for inspection, testing, and maintenance.

Fire dampers do not operate in isolation. They are one part of a wider fire strategy that includes structural compartmentation, detection systems, evacuation planning, and mechanical ventilation design. If any component fails to perform as intended, the compartmentation strategy can be compromised.

For this reason, DW 145 places strong emphasis on correct damper selection, installation to tested details, and ongoing inspection in line with the damper type and building use. All fire dampers form part of the life safety systems within a building and are subject to regulation under the Building Regulations, the Fire Safety Order, and, where applicable, the Building Safety Act.

Key British Standards For Fire Dampers

Fire dampers used in the United Kingdom must comply with a series of harmonised British and European standards. These standards cover product testing, classification, installation, and application. They work together to ensure that fire dampers perform reliably under fire conditions and are suitable for their intended use.

The key standards applicable to fire dampers include the following:

• BS EN 15650
  This is the product standard for fire dampers. It defines the essential performance characteristics that manufacturers must declare, including airflow resistance, closing time, and fire resistance. Dampers placed on the UK market must be CE- or UKCA-marked in accordance with this standard.
• BS EN 1366-2
  This is the fire resistance test standard for fire dampers. It specifies the conditions under which a damper must be tested, including duct configuration, fire exposure, mounting orientation, and supporting construction. All tested data used to support classification must be based on this standard.
• BS EN 13501-3
  This is the classification standard. It provides the format and terminology for fire resistance ratings, including integrity (E), insulation (I), and smoke leakage (S). It also defines the permitted classification periods and the manner in which to present test results.
• BS EN 15882-2
  This standard defines the extended field of application (EXAP) rules for fire dampers. It allows certain installation variations to be deemed acceptable without retesting, provided the conditions meet the rules laid out in the standard. Where an extended application is used, documentation must be available to justify its use.

These standards work in conjunction with regulatory requirements under the Building Regulations. Compliance is not limited to product performance. It also includes correct installation, sealing methods, support systems, and access for maintenance.

DW 145 refers to each of these standards where applicable and provides guidance on how to apply them correctly during design, specification, installation, and inspection. It also explains the limitations of these standards and highlights areas where manufacturer instructions must be followed without deviation.

Only fire dampers that are tested and classified to these standards can be considered compliant. Use of non-certified products or installation methods not covered by test evidence or an EXAP report may fail to meet the requirements of Approved Document B or the Fire Safety Order.

When Fire Dampers Are Required in HVAC Systems

Fire dampers are required wherever ventilation ductwork or air transfer paths penetrate fire-resisting elements of a building. These elements may include compartment walls, floors, protected shafts, or enclosures designed to limit the spread of fire and smoke. The purpose of the fire damper is to maintain the fire resistance of these elements by closing automatically under fire conditions.

The specific need for a fire damper depends on several factors:

• The location of the duct in relation to compartment lines
• The fire resistance rating of the wall or floor being penetrated
• The presence of protected escape routes or sleeping accommodation
• The building's fire strategy, including evacuation methods and space risk

DW 145 provides detailed guidance on when a fire damper is required. It distinguishes between typical applications, such as compartment walls between flats or escape corridors, and more complex layouts involving smoke control zones or firefighting shafts.

Examples of locations where fire dampers are commonly required include:

• Ducts passing through compartment walls or floors
• Ducts entering protected escape routes
• Ventilation systems serving sleeping areas, such as hotels or student accommodation
• Openings into pressurised stairwells or firefighting lobbies
• Transfer grilles in walls separating fire compartments

In many cases, a mechanical fire damper (FD) may be sufficient. However, where smoke leakage or insulation is a concern, a motorised damper with an ES or EIS classification may be required. DW 145 outlines which classification types are appropriate for each use case.

It is the responsibility of the system designer to determine when a fire damper is required and to specify the correct product type. The decision must be based on the fire compartmentation layout, the required fire-resistance duration, and the intended use of the space. Incorrect omission of a fire damper, or selection of the wrong type, may compromise life-safety systems and lead to non-compliance with the Building Regulations.

Selecting The Right Fire Damper For Your Application

Selecting the correct fire damper for each application is a critical part of the fire strategy and ventilation system design. It involves more than choosing a product with the required fire resistance period. The damper must also be suitable for the building layout, the space's risk level, and the type of supporting construction.

DW 145 outlines the process for selecting the correct fire damper. This includes reference to damper classification, orientation, installation conditions, and the fire strategy assumptions made during building design.

Key factors to consider include:

• Fire-resistance period: The damper's classification must match or exceed the fire-resistance requirement of the wall or floor it penetrates.
• Integrity, insulation and smoke leakage: Spaces such as escape routes, sleeping accommodation and refuge areas typically require dampers with ES or EIS classification to limit smoke spread and radiant heat.
• Duct orientation and fire direction: Dampers must be tested in the same orientation and in the direction of the proposed fire exposure as the proposed installation. For example, a floor installation requires horizontal classification.
• Compatibility with supporting construction: A fire damper must be tested for the specific wall or floor type, including thickness, density and fixing arrangement.
• Operational requirements: In systems that require remote actuation, automatic testing or position feedback, a motorised damper is typically required.
• Access and maintenance: Fire dampers must be installed with appropriate access for inspection and testing. Some locations may be unsuitable for fusible link dampers due to access constraints.

DW 145 also emphasises the importance of using fire dampers that have valid product certification, are installed in accordance with tested installation details, and are supported by documentation. Selection should not rely on generic descriptions or assumed performance.

Incorrect product selection remains one of the most common causes of non-compliant installations. Where classification requirements are unclear or where installation conditions differ from tested details, consultation with the manufacturer or a competent fire engineer may be required.

DW 145 Guidance For Fire Damper Selection And Specification

DW 145 is the recognised industry guide for the installation and maintenance of fire dampers within the United Kingdom. It is published by the Building Engineering Services Association and is referenced by designers, contractors, inspectors, and building control professionals. The document consolidates best practice across the design, installation, commissioning, and maintenance of fire dampers and provides a specific interpretation of the relevant British and European standards.

With regard to selection and specification, DW 145 guides on:

• Damper classification based on fire resistance period, smoke leakage, and insulation
• Suitable product types for different building layouts and risk categories
• Installation configurations, including duct orientation, supporting construction, and fixing methods
• Access, testing, and maintenance considerations that must be accounted for at the design stage
• Common causes of non-compliance include incorrect installation or failure to follow manufacturer instructions

The guide also supports the requirements of the Building Regulations, the Fire Safety Order, and the Building Safety Act. It aligns damper selection with wider compartmentation strategy, fire risk management, and the principles of the golden thread of building safety information.

DW 145 distinguishes between the different roles involved in the damper lifecycle. It addresses the responsibilities of the designer in specifying the correct product, the installer in delivering tested and certified installations, and the facilities team in ensuring ongoing maintenance and inspection.

All specifications must be based on tested and classified products, installed in accordance with the manufacturer's test evidence or extended application. Any deviation from tested conditions must be supported by appropriate documentation or engineering judgment. Selection based on catalogue data or assumed performance is not considered acceptable.

Further Reading

The following resources expand on key topics related to fire damper compliance and good practice under DW 145. The first link is our main reference guide. It is the central article in this content series and outlines the complete regulatory framework for the specification, installation, testing, and maintenance of fire dampers.

• Fire Dampers For Fire Safety And Building Regulations Compliance
• Damper Testing Requirements And UK Compliance Standards
• Fire Damper Installation Standards For UK Building Regulations