Preparing Your Smoke Shaft for a Successful Air Test

Achieving a compliant air test for your smoke shaft is a critical step toward project sign-off, especially for systems designed for Automatic Opening Ventilation (AOV). With strict airtightness targets and challenging access conditions, careful planning and preparation are essential.

Here’s our practical roadmap to help you pass your smoke shaft air test first time.

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Know Your Airtightness Target

Smoke shafts serving AOV systems are typically required to achieve an airtightness level of less than 3.8 m³/h/m² @ 50 Pa.

This is a stringent standard, particularly when you consider the relatively small envelope area of smoke shafts compared to their internal volume. Even minor gaps or incomplete sealing can result in a failed test.

Understanding your target early allows you to plan construction and sealing strategies accordingly.

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Seal All Potential Leakage Paths

Smoke shafts are often constructed from a mix of materials. Each element must be carefully sealed to ensure compliance.

Concrete Casting

Concrete walls generally provide the most robust and airtight barrier.

Blockwork

High-density blocks perform well, provided mortar joints are continuous and free from gaps.

Stud Wall and Plasterboard

Particular attention is required here. Ensure:

• Full sealing between plasterboard panels
• Proper sealing at junctions with concrete elements
• No service penetrations left untreated

Penetrations and Openings

Any opening within the shaft wall must be sealed internally, including:

• Service penetrations
• AOV fans
• Louvres
• Shutters
• Floor grilles

Use appropriate sealing methods such as:

• Taping and jointing
• Fire stopping materials
• Mastic or expanding foam

All sealing should be completed from inside the smoke shaft to prevent hidden leakage paths.

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Timing of the Air Test

The timing of your air test is just as important as preparation.

The test should take place when:

• The smoke shaft is fully constructed and sealed
• AOV fans and louvres/shutters are not yet installed
• All AOV doors are shut
• The top of the shaft is temporarily sealed

Testing at the correct stage avoids unnecessary retesting and programme delays.

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The Smoke Shaft Air Test Method

Smoke shaft testing should be carried out by a UKAS-accredited, ATTMA-registered company using pressurisation in accordance with CIBSE TM23 methodology.

The process typically involves:

• Selecting the correctly sized blower door fan to fit within a shaft opening (ideally midway up the shaft)
• Installing the fan into a temporary board sealing one of the louvre or shutter openings
• Pressurising the shaft using a UKAS-calibrated blower door system

The test itself takes only a few minutes, although the total site time is usually around 3–4 hours.

The shaft is tested to confirm it achieves the required 3.8 m³/h/m² target.

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What If the Smoke Shaft Fails?

Due to restricted access, identifying leakage paths inside a smoke shaft requires specialist techniques.

Diagnostic Methods Include:

1. Smoke Testing
The shaft is pressurised and theatrical smoke is introduced using high-powered smoke machines. Escaping smoke highlights cracks and gaps.

2. Thermal Imaging Surveys
The shaft is heated and pressurised while thermal cameras detect areas of heat loss.

3. Multi-Level Spotters
Operatives positioned on multiple floors identify leakage points while the engineer controls the test equipment.

All findings should be documented in a formal air leakage report and reviewed with the client before leaving site.

If smoke testing is required, notify relevant parties—including the local fire brigade—and consider restricting access during and shortly after testing while smoke disperses.

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How APT Can Help You Pass Your Smoke Shaft Air Test

At APT Sound Testing, our engineers have over 10 years of specialist experience in smoke shaft testing. We understand the common failure points—and more importantly, how to prevent them.

Our premium smoke shaft testing service includes:

• Pre-test smoke shaft survey visits by experienced consultants
• Testing by a UKAS-accredited, ATTMA Level 2 air testing company
• Official UKAS smoke shaft air test certification
• The latest high-powered fan equipment
• Fully UKAS-calibrated testing systems
• Diagnostic leakage surveys using smoke machines and thermal imaging
• Rapid response and testing turnaround

We provide expert design advice, consultancy, and compliance support across your entire project, delivering a professional and stress-free experience from start to finish.

For more information about our smoke shaft air testing services, contact APT Sound Testing on 01525 303905 or email info@airpressuretesting.net.

Preparing Your Smoke Shaft for an Air Tightness Test

Elevate fire safety standards with comprehensive air tightness testing and remediation.
Accredited Air Pressure Testing (APT) solutions help you meet regulatory requirements, improve smoke control performance, and protect building occupants.

Ensuring the safety and compliance of smoke shafts is a critical component of any building’s fire safety strategy. Smoke shafts are designed to restrict the spread of smoke and heat during a fire, protecting escape routes and supporting effective evacuation.

To confirm they perform as intended, air tightness testing is essential. Proper preparation can significantly increase the likelihood of passing the test first time and avoiding costly remedial works.

Top 10 Ways to Prepare a Smoke Shaft for Air Tightness Testing

1. Consult Smoke Shaft Testing Experts Early
   Engage air tightness consultants who specialise in smoke shaft testing at an early stage. Their expertise can guide effective design decisions, detailing, and sealing strategies.
2. Set Clear Airtightness Targets
   Establish the required airtightness performance—typically less than 3.8 m³/h/m² @ 50 Pa. Be aware that some smoke shafts may require different targets, so always confirm the specification in advance.
3. Use Robust Construction Materials
   Construct the shaft using materials capable of forming an effective air barrier, such as in-situ concrete or high-density blockwork.
4. Seal Internal Finishes Thoroughly
   Treat the internal surface of the smoke shaft as the primary air seal line. Finishes should be smooth and fully sealed at all joints and junctions, particularly where steelwork or other elements penetrate the shaft.
5. Seal All Service Penetrations
   Ensure all service, structural, and cable penetrations through the shaft envelope are carefully sealed using appropriate fire- and air-rated products.
6. Seal Door Openings Effectively
   All access doors within the smoke shaft should be fully sealed using robust, heavy-duty sealing systems to prevent air leakage.
7. Seal AOV Door Frames
   The perimeter of Automatic Opening Vent (AOV) door frames must be fully mastic sealed to maintain continuity of the air barrier.
8. Seal the Base and Head of the Shaft
   Pay close attention to the base and head of the shaft, ensuring both are fully sealed prior to testing.
9. Use Calibrated Testing Equipment
   Testing should be carried out using a UKAS-calibrated blower door fan, capable of pressurising the smoke shaft and accurately measuring air leakage.
10. Address Any Test Failures Promptly
    If the smoke shaft does not achieve the required performance, diagnostic methods such as smoke testing and thermal imaging should be used to locate leakage paths and guide targeted remedial works.

By following these steps, you can ensure your smoke shaft is properly prepared for air tightness testing, improving compliance with current building regulations and enhancing overall fire safety.

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Why Choose APT for Smoke Shaft Air Tightness Testing?

APT has extensive experience supporting clients with smoke shaft testing across projects of all sizes. We also provide a dedicated diagnostic service for failed smoke shafts, using smoke testing and thermal imaging to accurately identify air leakage paths within the shaft envelope.

On many projects where smoke shafts initially failed, our engineers have rapidly located leakage points, enabling targeted remedial works and successful re-testing with minimal disruption.

Our UKAS-qualified and fully trained engineers are highly knowledgeable in current industry standards and testing methodologies. This expertise allows us to provide clear, actionable recommendations to improve the performance of your smoke shafts.

Air Pressure Testing is one of the few companies in the UK that is both UKAS-accredited and ATTMA Level 2 accredited for air tightness testing of buildings, smoke shafts, and floor plenums. This ensures all testing is carried out in line with regulatory requirements and recognised best practice, giving you complete confidence in the results.

Smoke Shaft Air Testing: Pass First Time

Smoke shafts play a crucial role in fire safety within high-rise buildings. As a key part of a building’s smoke control system, they’re designed to help manage smoke movement during a fire, keeping escape routes clearer for longer. Because of this vital function, the air-tightness of a smoke shaft isn’t optional—it’s essential.

Most smoke shafts must meet a strict air-tightness target (typically 3.8m³/hr/m²). If they fail to achieve this standard, it can compromise the performance of the entire smoke control system, leading to delays in sign-off from fire system contractors or Building Control.

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Experts in Smoke Shaft Testing & Diagnostics

With extensive experience across smoke shafts of all sizes, we’ve helped countless clients achieve compliant test results. If a shaft fails its initial test, our diagnostic service quickly locates leakage paths using a combination of:

• Smoke testing
• Thermal imaging

This approach allows us to pinpoint exactly where air is escaping. We compile these findings into a clear, detailed air leakage report so that targeted remedial sealing can be carried out efficiently. In most cases, clients achieve a successful pass on the follow-up test.

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Our Premium Smoke Shaft Testing Service Includes:

• Comprehensive smoke shaft survey visits by experienced consultants
• Testing carried out by a UKAS and ATTMA Level 2 accredited air testing company
• Official UKAS/ATTMA-compliant smoke shaft air test certification
• State-of-the-art, high-powered fan and UKAS-calibrated equipment
• Industry-leading diagnostic services using smoke machines and thermal imaging
• Fast, reliable turnaround with our rapid testing service

Air Pressure Testing is one of the few companies accredited to both UKAS and ATTMA Level 2 for air tightness testing of buildings, smoke shafts, and floor plenums.

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Works to the Smoke Shaft: 

Certain events may require additional testing:

• Alterations to the smoke shaft:If modifications are made to the fabric of the smoke shaft or adjacent areas, retesting is necessary.
• Fire Incidents:After a fire incident, smoke shafts should be inspected and tested to confirm their ongoing integrity.
• Building Occupancy Changes:If the building’s use changes significantly, retesting may be required, i.e. an office building to residentialConsult Local Authorities and Experts:Always consult with local fire safety authorities, building control officers, or fire engineers. They can provide specific guidance based on regional regulations and best practices.

Remember that maintaining properly functioning smoke shafts is essential for occupant safety during fires. Regular testing ensures their reliability and effectiveness in smoke extraction.

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Need Smoke Shaft (AOV) Testing or a Checklist?

If you’d like more information about our smoke shaft testing services, or want to download our smoke shaft checklist, contact us by calling 01525 303905 or visit our website at:
www.aptsoundtesting.co.uk

We’re here to help you achieve compliance quickly, efficiently, and with confidence.