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Fire Door Intumescent Seals: Maintenance and Replacement Guide

Fire doors represent a crucial element in any building’s passive fire protection strategy. However, even the most robustly constructed fire door will fail to perform its life-saving function without properly functioning intumescent seals. At Neo, our fire door maintenance experience involves maintaining thousands of fire doors across multiple sectors. Seal issues are among the most common yet overlooked defects we encounter during fire door repairs, often compromising fire door performance.

Intumescent seals play a vital role in fire door assemblies by expanding when exposed to heat, sealing the gaps around the door and preventing the passage of smoke and flames. This seemingly small component can mean the difference between a fire being contained and it spreading rapidly throughout a building, potentially costing lives and causing extensive property damage.

In this blog post we’ll explore everything building safety managers, fire safety advisors, and maintenance heads need to know about maintaining, inspecting, and replacing intumescent seals across their estates.

Understanding Intumescent Seals: Types and Functions

What Are Intumescent Seals?

Intumescent seals are specialised strips, typically made from materials that expand when exposed to heat (usually around 200°C, depending on the material composition). These seals are designed to close the necessary operational gaps around fire doors—gaps that would otherwise allow smoke and flames to pass through during a fire.

Types of Intumescent Seals

There are several variations of intumescent seals used in fire door assemblies:

1. Standard Intumescent Strips

Basic seals that expand when heated
Typically installed in grooves in the door frame or leaf edge
Available in various widths and thicknesses to suit different door configurations

2. Combined Intumescent/Smoke Seals

Feature an additional flexible fin or brush that provides a smoke seal at ambient temperatures
The most common type specified in modern buildings
Offer dual protection against both fire and cold smoke

3. Concealed Seals

Installed within the door edge or frame out of sight
Provide a cleaner aesthetic appearance
Often used in heritage buildings or high-end commercial spaces

4. Glazing Seals

Specialised intumescent materials used around glazed apertures in fire doors
Typically in tape or gasket form
Essential for maintaining the integrity of glazed sections during a fire

How Intumescent Seals Work

In normal conditions, intumescent seals remain dormant and allow the door to function as required. When exposed to the heat of a fire, the intumescent material rapidly expands up to 5–20 times its original volume depending on the material type and formulation, creating a pressure-tight seal that blocks the transmission of hot gases, smoke, and flames.

This expansion process is crucial in a fire scenario as it:

Compensates for any warping of the door due to heat
Fills operational gaps necessary for door function
Creates a barrier that maintains the door’s fire-resistance rating
Prevents the passage of hot gases which could ignite materials in adjacent compartments

Regulatory Requirements for Intumescent Seals

Understanding the regulatory landscape is essential for anyone responsible for fire door maintenance. Current UK regulations require:

Fire Safety (England) Regulations 2022

Mandates regular checks of fire doors, including seals
Requires quarterly checks in multi-occupied residential buildings
Creates specific responsibilities for the “Responsible Person”

Regulatory Reform (Fire Safety) Order 2005

Article 17 requires that fire-resisting doors are subjected to a “suitable system of maintenance”
Intumescent seals are specifically considered a critical component requiring regular checking

Building Regulations Approved Document B

Specifies requirements for fire door performance, including the role of intumescent seals
Outlines locations where fire doors with appropriate seals must be installed

BS 9999 and BS 8214

Provide guidance on the specification and installation of intumescent seals
Outline best practices for maintenance and inspection

As the Responsible Person under these regulations, ensuring properly functioning intumescent seals is not just good practice – it’s a legal requirement with serious consequences for non-compliance.

Intumescent Seals and Routine Fire Door Maintenance

Intumescent seal checks should be a core part of any regular fire door maintenance programme. Missing or damaged seals can compromise fire resistance ratings, so maintaining them is essential for long-term door compliance and building safety.

Based on our experience across thousands of fire doors, we recommend the following approach:

Frequency of Inspections

High-traffic areas: Quarterly inspections
Standard-use areas: Bi-annual inspections
Low-use areas: Annual inspections at minimum
After any incident: Immediate inspection following any event that may have damaged doors or frames

What to Look For

When inspecting intumescent seals, check for:

Physical damage: Cuts, tears, or sections missing from the seal
Correct positioning: Seals should be continuous and correctly located in their grooves
Paint contamination: Seals should not be painted over as this impairs functionality
Compression damage: Excessive compression from door closing can damage seals over time
Secure fixing: Ensure seals remain firmly fixed in their channels
Appropriate specification: Confirm seals match the door’s fire rating and configuration
Age deterioration: Material degradation due to age or environmental conditions
Compatibility: Ensure seals are compatible with the door design and certification

Documentation Requirements

For each inspection, maintain records that include:

Date of inspection
Door reference or location identifier
Condition of seals
Any actions taken or required
Photographic evidence
Inspector identification

This documentation forms a crucial part of your building’s “Golden Thread” of information and provides evidence of compliance with regulatory requirements.

The Role of Intumescent Seals in Fire Door Repairs

Fire door repairs often involve replacing worn, damaged, or non-compliant intumescent seals. These small but critical components are among the most common causes of fire door failure and should be inspected and repaired as part of any comprehensive fire door maintenance programme.

Common Fire Door Repairs related to Intumescent Seals

1. Missing or Damaged Seals

Problem: Sections of seal completely absent or visibly damaged.
Solution: Complete replacement of the affected seal length is required. Partial repairs or overlapping of new sections is not acceptable. Replacement seals must match the fire door’s third-party certification data or field of application documents.

2. Painted-Over Seals

Problem: Seals covered with paint during decoration, impeding their ability to expand properly.
Solution: Remove and replace affected seals. Advise decoration contractors on proper procedures for future work.

3. Poorly Fitted Seals

Problem: Seals that are loose, protruding, or improperly fitted in their grooves.
Solution: Remove and reinstall correctly, ensuring proper adhesion and positioning. If grooves are damaged, specialist repair may be required.

4. Incorrect Specification

Problem: Seals that don’t match the fire rating or configuration required for the specific door.
Solution: Replace with correctly specified seals according to the door’s certification or fire strategy requirements.

5. Excessive Gap Sizes

Problem: Door gaps exceeding tolerances, making the intumescent seals ineffective.
Solution: Address the door alignment issues first, then assess whether the existing seals are sufficient or if wider seals are required. Generally, BS 8214 and BS 9999 recommend gaps no more than 3mm at the sides and top, and up to 10mm at the threshold (unless otherwise tested).

6. Environmental Damage

Problem: Seals degraded due to exposure to cleaning chemicals, extreme temperatures, or high humidity.
Solution: Replace affected seals and address environmental factors where possible. Consider alternative seal types if the environment cannot be modified.

If you’re planning fire door repairs across your estate, Neo can help you stay compliant with fast-turnaround seal replacement and full BM TRADA-accredited repair services.

Replacing Intumescent Seals: BM Trada Approved Repair Techniques

At Neo, we are certified under the BM TRADA Q-Mark Fire Door Maintenance Scheme and follow their strict guidelines for all repairs. When replacing intumescent seals, we adhere to the following official BM Trada Accepted Repair Technique (ART):

ART 11 – Damaged perimeter seals – This accepted repair technique is only valid when carried out by a company that is certified under the BM TRADA Q-Mark Fire Door Maintenance Scheme and in accordance with the scheme requirements.

Description of damage: Perimeter intumescent seals are damaged, partly missing, or combined intumescent & smoke seals have been painted or damaged.

The entire section of damaged intumescent seal must be removed and replaced on a ‘like for like’ basis with a seal of the same specification. Including:

1. Dimension

2. Manufacturer

3. Intumescent type

4. Configuration

5. Profile (if the seal includes fins or brush seals for other performance characteristics for example smoke, weather, or acoustics).

It is possible to replace a section of seal where a joint is present in the length of the existing seal (as depicted in the images below). Close inspection of the remaining or damaged seal will often provide information printed on the seal with respect to identifying the manufacturer and seal type.

If it is not possible to identify the specification of the seal (as defined above) the seal should be replaced with an approved specification as determined by the doorset manufacturer.

This ART covers the following:

1. Replacement of a damaged or missing intumescent or combined intumescent & smoke seal.

2. Where an existing seal is not deliberately jointed, the entire length of seal must always be replaced (with no butt joints present)

3. Where existing seals are deliberately jointed (i.e., anti-ligature requirements), the whole damaged or missing seal must be replaced between joints in the seal. It is only then possible to include butt joints to match the existing specification as installed.

This ART does not cover:

Replacement of intumescent seals which are not supported by test evidence. If it is not possible to determine a suitable replacement seal via the door manufacturer this ART must not be applied.

Special Considerations for Different Building Types

Different sectors present unique challenges for intumescent seal maintenance:

Social Housing

High tenant turnover requires more frequent inspections
Education on not painting over or removing seals is essential
Addressing damage promptly prevents further deterioration
Standardisation across large estates simplifies maintenance

Educational Institutions

Seasonal access challenges during term times
High traffic in certain areas leads to accelerated wear
Historical buildings may require specialised approaches
Scheduling work during vacation periods minimises disruption

Healthcare Facilities

Infection control considerations when handling materials
24/7 operation limits maintenance windows
More frequent cleaning regimes can accelerate seal deterioration
Critical areas require minimal downtime

Hospitality Venues

Guest experience concerns during maintenance
Variable usage patterns across different areas
Aesthetic considerations in high-end establishments
Minimising room downtime is essential for revenue protection

Cost-Effective Maintenance Strategies

Proactive fire door maintenance, including the planned replacement of intumescent seals, ensures compliance and reduces long-term costs. Implementing a strategic approach to intumescent seal inspection and repairs delivers significant improvements to Fire Door Maintenance strategies:

Preventative Replacement Programmes

Rather than waiting for failure, consider:

Scheduled replacement based on known lifespan
Prioritising high-risk or high-traffic areas
Combining seal replacement with other maintenance activities
Bulk purchasing for consistent quality and cost savings

Training In-House Staff

Developing internal capabilities:

Train maintenance teams to identify seal issues during routine inspections
Provide education on the importance of seals to all staff
Develop clear reporting mechanisms for damaged seals
Create standard operating procedures for basic maintenance

Technology Solutions

Leverage technology for efficient management:

Digital record-keeping of seal condition and replacement dates
QR codes on doors linking to maintenance history
Mobile applications for on-site inspection recording
Automated scheduling of inspection cycles

A Strategic Approach to Intumescent Seal Management

Intumescent seals may represent a small component of your fire safety strategy, but their impact on fire door performance is significant. By implementing a proactive, strategic approach to seal inspection and maintenance, building managers can:

Ensure regulatory compliance and reduce legal exposure
Extend the service life of fire doors through timely seal replacement
Optimise maintenance budgets through planned rather than reactive work
Enhance overall building safety and protect occupants
Maintain comprehensive documentation for the Golden Thread

As with all aspects of fire safety, a repairs-first approach that identifies and addresses seal issues before complete door replacement is necessary delivers both safety and financial benefits.

About Neo: Your Partner in Fire Door Compliance

Neo, part of PTSG’s Fire Solutions division, delivers advanced passive fire protection services across the UK. We work with a diverse range of large organisations responsible for thousands of fire doors, including social housing providers, local authorities, healthcare trusts, educational institutions, student accommodation providers, and security-sensitive offices.

Our repairs-first approach to fire door maintenance includes comprehensive intumescent seal inspection and replacement services. With our team of directly employed specialists working under third-party accreditation, including the BM TRADA Q-Mark Fire Door Maintenance Scheme, we provide peace of mind that your fire doors will perform as intended when needed.

Neo’s technical expertise, combined with the Bolster system for comprehensive documentation, ensures that your intumescent seal maintenance contributes to a robust Golden Thread of information. From individual seal replacements to estate-wide maintenance programmes, we deliver compliant, cost-effective solutions tailored to your specific needs.

For a complimentary review of your intumescent seal maintenance strategy or to discuss how Neo can help with your fire door compliance, contact us at [email protected].