Guide to Installing Fire Dampers & Fire Rated Ducting
Guide to Installing Fire Dampers & Fire Rated Ducting
Ventilation ductwork often needs to pass through walls, floors and other parts of a building designed to resist the spread of fire.
Where this happens, the ventilation system must be designed so that it does not compromise the building's fire compartmentation.
Fire dampers and fire-rated ducting are two important solutions used to help maintain fire resistance where ventilation services pass through or between fire compartments.
This guide explains what they do, where they may be required and the key factors to consider when planning and installing them.
What Is a Fire Damper?
A fire damper is installed within a ventilation opening or duct where it passes through a fire-resisting wall, floor or other compartment boundary.
During normal operation, the damper allows ventilation air to pass through.
If a fire occurs, the damper is designed to close and help prevent fire from spreading through the ventilation duct into another part of the building.
Depending on the application, different types of dampers may be used, including:
- Fire dampers
- Fire and smoke dampers
- Mechanical or spring-operated dampers
- Motorised dampers
- Intumescent fire dampers
The correct type depends on the ventilation system, fire strategy and performance required.
What Is Fire-Rated Ducting?
Fire-rated ducting, also known as fire-resisting ductwork, is designed and tested to maintain a specified level of fire resistance for a defined period.
Rather than relying solely on a damper at a compartment boundary, fire-rated duct systems can be used where the duct itself needs to maintain fire resistance as it passes through the building.
These systems may be required for applications such as:
- Ventilation ductwork
- Smoke extract systems
- Kitchen extract systems
- Escape route protection
- Services passing through fire compartments
The exact requirements depend on the building and the purpose of the duct system.
Ventilation Superstore's fire solutions range includes products for projects where fire protection needs to be considered alongside ventilation ductwork.
Why Fire Compartmentation Matters
Buildings can be divided into fire compartments using fire-resisting walls and floors.
The purpose of compartmentation is to restrict the spread of fire and smoke from one part of a building to another for a specified period.
However, building services still need to pass through these barriers.
This can include:
- Ventilation ducts
- Pipes
- Electrical cables
- Drainage
- Other mechanical services
Every penetration creates a potential weak point.
If ventilation ductwork simply passes through a fire-resisting wall without an appropriate tested solution, the fire performance of the compartment may be compromised.
Fire dampers, fire-rated ductwork and suitable fire-stopping systems therefore need to be considered as part of the complete design.
Check the Fire Strategy Before Installation
Before selecting or installing fire protection products, identify what level of fire resistance the building requires.
This may be specified within:
- Architectural drawings
- Mechanical and electrical drawings
- Fire strategy documentation
- Building control requirements
- Product specifications
Do not assume that the same damper or fire-rated duct system will be suitable everywhere in the building.
Different compartment boundaries can have different fire-resistance requirements.
For projects in England, Approved Document B provides statutory guidance on fire safety under the Building Regulations.
Requirements vary across the UK and Ireland, so the regulations and fire strategy applicable to the specific project should always be followed.
Choosing the Correct Fire Damper
A fire damper should be selected according to its intended application and required fire performance.
Important factors include:
- Required fire-resistance classification
- Wall or floor construction
- Duct size
- Duct orientation
- Damper type
- Installation method
- Smoke-control requirements
- Access for future inspection
- Manufacturer's tested installation detail
Fire dampers used within ventilation systems should not be selected simply by matching the duct diameter.
The complete damper and supporting construction need to form a suitable tested arrangement.
Approved Document B states that fire dampers should conform to BS EN 15650 and should achieve the required fire-resistance classification for the application.
Where Should a Fire Damper Be Installed?
Fire dampers are commonly associated with locations where ventilation ductwork penetrates a fire-separating element.
The exact location is important.
Approved Document B states that fire dampers and fire-and-smoke dampers should be located within the thickness of the fire-separating element, securely fixed and positioned so that movement or expansion of the ductwork during a fire does not push the damper through the structure.
Installation should therefore follow the damper manufacturer's tested detail rather than using a generic installation method.
Don't Forget Access for Maintenance
A fire damper should remain accessible after the rest of the building has been completed.
This is important because the damper and its operating mechanism need to be inspected and maintained throughout the life of the building.
Access panels may therefore need to be incorporated into:
- Ceilings
- Ductwork
- Service enclosures
- Risers
Approved Document B specifically requires access to fire dampers and their actuating mechanisms for inspection, testing and maintenance.
Blocking a damper permanently behind plasterboard or another inaccessible building finish can create problems later.
Installing Fire-Rated Ductwork
Fire-rated ductwork should be treated as a complete system rather than a standard duct with individual fire-resistant components added to it.
Its performance can depend on:
- Duct material
- Joint construction
- Supports and hangers
- Fixings
- Penetration details
- Fire-resistant insulation or enclosure
- Orientation
- Duct dimensions
- Distance between supports
Changing one part of the tested assembly can affect the fire performance of the complete system.
For this reason, the manufacturer's approved installation instructions and classification documentation should always be followed.
Fire-resisting ventilation ducts are tested under standards including BS EN 1366-1, which assesses the ability of duct assemblies to resist the spread of fire between compartments.
Fire Dampers vs Fire-Rated Ducting
Although both provide fire protection, they do different jobs.
| Solution | Main Purpose |
|---|---|
| Fire Damper | Closes a ventilation opening where ductwork passes through a fire-resisting barrier |
| Fire & Smoke Damper | Helps restrict the spread of both fire and smoke |
| Fire-Rated Ducting | Allows the duct system itself to maintain fire resistance for a specified period |
| Fire Stopping | Seals gaps around service penetrations to help maintain the compartment boundary |
A project can require more than one of these solutions.
The fire strategy and tested system details should determine what is required rather than treating them as interchangeable products.
Fire Stopping Around the Penetration
Installing the damper or fire-rated duct is only one part of maintaining the compartment.
The opening around the penetration may also need an appropriate fire-stopping system.
This needs to be compatible with:
- The wall or floor construction
- The damper or duct
- The size of the penetration
- The required fire rating
- The tested installation detail
Using general-purpose filler or an untested combination of products around a fire damper should be avoided.
The complete penetration needs to perform as intended as part of the fire-resisting construction.
Support and Fixing Are Important
Ventilation ductwork needs appropriate support even during normal operation, but this becomes particularly important where fire protection is involved.
Supports, brackets and fixings should follow the specification for the tested system.
Fire can cause ductwork to expand, distort or place additional loads on surrounding components.
Incorrectly supported ductwork could therefore affect the performance of a damper or fire-rated penetration.
This is why the fixing and support arrangement should not be changed from the manufacturer's approved system without appropriate evidence.
Plan Fire Protection With the Duct Layout
Fire protection is much easier to incorporate when ventilation routes are planned early.
Ideally, identify:
- Where ducts will run
- Where they cross fire compartment boundaries
- What fire rating each boundary requires
- Which type of damper or fire-rated duct system is required
- Where inspection access will be provided
- How the ductwork will be supported
Trying to add fire dampers after the duct system has already been installed can result in awkward access, unsuitable locations or additional alterations.
If you are still planning the ventilation system itself, our guide to understanding MVHR ducting explains the differences between duct types, sizing, routing, insulation and other duct-design considerations.
Common Fire Damper Installation Mistakes
Some common issues to avoid include:
Installing the wrong damper for the application
A damper should have the correct classification and be suitable for the particular wall, floor and duct arrangement.
Positioning the damper incorrectly
Fire dampers need to be installed in the position defined by the tested installation method and fire strategy.
Not providing inspection access
The damper must remain accessible for future inspection, testing and maintenance.
Using incompatible fire-stopping products
The fire-stopping arrangement should form part of an appropriate tested system.
Poor duct support
Duct movement during a fire should not compromise the damper or compartment penetration.
Altering the tested installation
Changing fixing methods, penetration sizes, supports or construction details can affect the performance of the complete fire-protection system.
Inspection and Maintenance
Fire dampers are passive fire-safety components, but they should not simply be installed and forgotten.
They need to remain accessible and should be inspected and maintained in accordance with the relevant requirements, fire-safety strategy and manufacturer guidance.
Checks may include the condition of:
- Damper blades
- Operating mechanisms
- Fusible links or actuators
- Fire stopping
- Duct connections
- Access panels
- Surrounding construction
Any inspection and maintenance regime should reflect the building's fire-safety management requirements.
Find Fire Protection Products at Ventilation Superstore
Correctly protecting ventilation penetrations is an important part of maintaining fire compartmentation within a building.
Fire dampers and fire-rated ductwork should be selected according to the project's fire strategy, required classification, building construction and tested installation details rather than treated as standard ventilation fittings.
Explore Ventilation Superstore's fire solutions for fire-protection products suitable for ventilation and ductwork projects.
Always follow the relevant building regulations, fire strategy and manufacturer's installation instructions, and use appropriately competent professionals where required.
