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BS 9991 · As Built Testing

Smoke Shaft Testing
for life safety compliance.

ATTMA Level 2 accredited smoke shaft air leakage testing for new build handover and existing buildings. Clear reports, early planning guidance, and consolidation with other completion tests.

BS 9991
2024 compliant
methodology
New & existing
buildings tested
across the UK

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Smoke shaft testing is a life safety requirement. Early engagement prevents costly delays to handover.

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A smoke shaft is a life safety device — not just a construction element.

Smoke shafts safely direct smoke, heat, and harmful gases away from escape routes during a fire. For the system to work, the shaft must be airtight. Testing proves it is.

Evacuation safety
During a fire, smoke extract must draw only from the fire floor. Air leaks elsewhere in the shaft reduce extraction effectiveness and allow smoke to migrate to non-fire floors, compromising escape routes.
Compartmentation integrity
The smoke shaft forms part of the fire compartmentation strategy. Leaks allow smoke to escape from the shaft into adjacent spaces on non-fire floors, breaching compartment boundaries.
Energy compliance
Under normal conditions, an airtight shaft prevents unwanted heat loss and satisfies Part L energy requirements. A leaking shaft fails on both fire safety and energy performance grounds.
Air tightness standard
3.8
m³/hr/m² at 50 Pa — maximum accepted leakage rate

The accepted industry benchmark for smoke shaft air tightness is 3.8 m³/hr/m² at 50 Pascals — a standard that originated as a recommendation from Colt and is now widely adopted across UK building practice. This is the threshold your smoke shaft must meet or beat to be considered compliant.

Your project specification, fire engineer, or local authority may require a tighter standard. Always confirm the applicable limit with your fire engineering team before installation begins — addressing this at the design stage is significantly easier and cheaper than remediation after construction.

Note that BS 9991:2024 is the current version of the standard for residential buildings. BS 9999:2017 applies to non-residential buildings. Both require testing at handover and periodic retesting throughout the building's life.

Smoke shaft testing happens in two stages.

A systematic approach is essential to deliver testing correctly, cost-effectively, and in accordance with ATTMA TSL guidelines. Early engagement with us helps align the testing programme with your build schedule.

01
Before testing
Preparation & Readiness

Before any testing begins, the shaft configuration, design drawings, and fire strategy documents are reviewed to understand the shaft's construction and define the scope of work. This stage is best planned early — well before the expected test date.

  • Review of fire strategy, PDF drawings, and smoke shaft layout
  • Check UKCA/CE marks and Declaration of Performance (DoP) certificates for all shaft components — dampers, AOVs, fans, and ductwork
  • Confirm power to main control panels is available
  • Pre-test walk of the shaft to identify potential leakage points before equipment is set up
  • Temporary sealing of AOVs from inside using tape, Correx, or Celotex board
  • Configuration of fan and test equipment to create a sealed test environment
02
During testing
Pressurisation & Measurement

A calibrated fan unit is used to pressurise or depressurise the shaft. By carefully measuring the airflow and pressure differential across the shaft envelope, our engineers determine the air leakage rate in accordance with ATTMA TSL Issue 1 and relevant BS EN standards.

  • Fan pressurises or depressurises shaft to test reference pressure
  • Airflow and pressure differential measured at multiple reference points
  • Results analysed against the required standard for the project
  • If leakage exceeds target, thermal imaging or smoke pencil used to locate sources
  • Detailed test report prepared with results, leakage rate, and certificate
  • Certificate issued for Building Control submission and Golden Thread records

Smoke shaft testing applies to new buildings and existing ones.

The regulatory obligation differs between new build handover and routine maintenance — but both are legally required.

New Build
Handover testing — required at completion

Smoke shaft testing at new build handover is a legal requirement under Approved Document B and BS 9991. It demonstrates that the as-built smoke ventilation system performs as designed, and a certificate is required for Building Control sign-off.

The smoke shaft is rarely delivered by a single party — it is typically constructed from components supplied and installed by different contractors at different stages of the build. It cannot be assumed that factory-certified components automatically combine to form a compliant, airtight shaft. The integrated system must be tested as a whole.

We recommend engaging us early in the programme to plan testing at the optimal construction stage, with sufficient allowance for remediation if needed. Late engagement risks delays to handover.

Existing Buildings
Routine testing — required throughout the building's life

The Fire Safety Act 2021 and Fire Safety Regulations (England) 2022 require building owners and responsible persons to conduct regular fire risk assessments and system testing throughout the life of the building. BS 7346-8:2013 provides detailed guidance on the testing and maintenance required.

Over time, building movement, minor repairs, and component wear can degrade smoke shaft airtightness. Annual testing helps verify system integrity and identify problems early — before they become serious or require major remedial work.

Test certificates, records, and date information must be stored securely as part of the building's official documentation to satisfy the principles of the Golden Thread and demonstrate ongoing compliance during inspections, audits, or building sale.

Most failures are avoidable with early attention to detail.

The majority of smoke shaft test failures stem from the same handful of issues — nearly all of which are far easier to address during construction than after the shaft is complete. We provide pre-test guidance at the point of booking and can carry out a pre-test inspection to identify problems before formal testing begins.

A key principle: the inside of the shaft should be treated as the primary air seal. Every joint, penetration, and junction on the internal face needs to be properly sealed with fire-rated mastic or jointing compound. Focusing sealing effort on the external face creates a system that looks correct but leaks at every internal gap.

Educating contractors and installers about the life safety implications of thorough sealing — particularly for cable penetrations and plasterboard joints — pays significant dividends at the test stage. A missed seal that is simple to fix during construction can require disruptive, expensive call-backs once finishes are complete.

Unsealed service penetrations Pipes, cables, and conduits passing through the shaft walls are a primary leakage source. Each penetration must be individually sealed — large cable bundles that are not separated are particularly difficult to seal effectively.
Plasterboard joints & screwheads unsealed Where internal plasterboard is used, all joints between sheets and all screwheads must be sealed so the finish acts as a continuous airtight barrier. Unsealed joints are among the most common test failures.
AOV frames & architraves Seals around Automatic Opening Vent frames are one of the most frequently missed areas. The frame-to-shaft junction must be sealed on the internal face. For testing, AOVs must be temporarily sealed from inside using tape, Correx, or Celotex board.
Access panel gaps Access panels and damper frames must be fully sealed at their perimeter. Even small gaps around access hatches can contribute meaningfully to overall leakage rate.
Component certification gaps Where individual shaft components lack valid UKCA/CE marks and DoPs, compliance of the overall system cannot be fully demonstrated even if the leakage rate passes. Check certification before construction completes.

The legislative and technical framework for smoke shaft testing.

Smoke shaft testing sits at the intersection of building regulations, fire safety legislation, and British Standards. Understanding which apply to your building is essential.

Building Regulations
Approved Document B
Sets out fire safety requirements for new buildings in England. Requires smoke shaft testing at handover as part of demonstrating compliance with the fire ventilation strategy.
British Standard
BS 9991:2024
Fire safety in the design, management, and use of residential buildings. The current standard governing smoke shaft design, testing, and ongoing maintenance in residential developments.
British Standard
BS 9999:2017
Fire safety in non-residential buildings. Sets out equivalent requirements for commercial and mixed-use developments with smoke control systems.
Primary Legislation
Fire Safety Act 2021
Clarifies the responsibilities of building owners for fire risk assessments covering the external envelope and structure of multi-occupied residential buildings.
Secondary Legislation
Fire Safety Regulations 2022
Requires responsible persons in higher-risk residential buildings to conduct and record regular fire risk assessments and system testing, including smoke control systems.
British Standard
BS 7346-8:2013
Components for smoke and heat control systems. Provides detailed requirements for the testing, servicing, and maintenance of smoke control systems throughout the life of a building.

Local ATTMA-accredited smoke shaft testers across the Midlands and South West.

Smoke shaft testing requires specialist equipment and expertise. Our ATTMA Level 2 accredited testers work across our core service areas with rapid mobilisation for urgent commissioning schedules.

Birmingham & West Midlands

Smoke shaft air tightness testing and commissioning for high-rise residential developments across Birmingham, Solihull, Coventry, Wolverhampton, and the wider West Midlands. BS 9991 and Approved Document B compliance.

Bristol & South West

Smoke control system testing across Bristol, Bath, South Gloucestershire, and the surrounding South West. AOV shaft pressurisation and fire damper commissioning for new build and existing buildings.

Worcestershire

Based in Worcester — smoke shaft testing across Malvern, Droitwich, Evesham, Bromsgrove, and Redditch. Our home county with the fastest mobilisation times.

Gloucestershire

Smoke shaft and AOV testing for residential developments across Cheltenham, Gloucester, Stroud, Tewkesbury, and the Cotswolds. Certificates accepted by all local Building Control and fire authorities.

Oxfordshire

BS 9991 smoke shaft compliance testing across Oxford, Banbury, Bicester, Witney, and the wider Oxfordshire area. New build and existing building assessments.

Wider England & Wales

As ATTMA Level 2 accredited testers, our smoke shaft certificates are valid across the whole of England and Wales. We regularly commission systems outside our core regions — contact us wherever your project is.

Looking for smoke shaft testing near you? Whether you have a high-rise residential block in Birmingham, a mixed-use development in Bristol, or an existing building requiring recertification in Gloucestershire — our ATTMA Level 2 testers deliver BS 9991 compliant results. Call 01386 365145 or email us to book.

Common questions about smoke shaft testing.

The widely accepted industry benchmark is 3.8 m³/hr/m² at 50 Pascals — a threshold originated by Colt and now adopted as standard practice across UK building projects. This is the level your smoke shaft must achieve to be considered compliant.

However, individual project specifications, fire engineers, or local authority requirements may specify a tighter standard. Always confirm the applicable limit for your project in the fire strategy documentation before installation begins. Discovering a more stringent requirement after construction is completed significantly increases the risk and cost of remediation.

Factory certification confirms that individual components perform to their product standard in isolation. It does not confirm that they have been correctly installed together as an integrated system, or that the junctions, penetrations, and joints between them have been properly sealed.

A smoke shaft is typically constructed by multiple contractors at different stages of the build. The combined result must be tested as a whole — because it is the whole system that will be relied upon in a fire, not the individual components.

Automatic Opening Vents must be temporarily sealed from the inside during the test to eliminate them as air leakage paths. The preferred method is to use tape, Correx board, or Celotex board secured to the internal face of the AOV frame.

Dampers alone should not be relied upon to seal AOVs for testing — they may not provide sufficient airtightness to give a valid result. Ideally, AOV sealing should be planned before the units are installed, as this makes achieving an effective seal significantly easier.

Following a successful test, we issue a full report including the test results, the measured air leakage rate, and a compliance certificate suitable for Building Control submission.

These records — along with component DoPs, maintenance logs, and subsequent test certificates — form part of the building's official documentation and must be maintained in accordance with the Golden Thread principles under the Building Safety Act 2022. Records are required for inspections, audits, building sale, and ongoing fire risk assessment compliance.

As early as possible — ideally during the pre-construction or early construction phase. Early engagement allows us to review the shaft design and fire strategy, flag any foreseeable compliance risks, and agree a testing programme that aligns with your build and completion schedule.

We strongly recommend planning for a pre-test inspection before final finishes are applied. At that stage, any leakage paths are still accessible and remediation is straightforward. Engaging late — when the shaft is complete and finishes are in — significantly limits your options if the test fails and adds risk of handover delays.

BS 7346-8:2013 and BS 9991:2024 both require smoke shaft systems to be tested and maintained throughout the building's life. Annual testing is generally recommended as part of a building's routine fire safety maintenance programme, alongside other life safety system checks.

The Fire Safety Regulations (England) 2022 place specific obligations on responsible persons in higher-risk residential buildings (those over 18 metres or with at least 7 floors). Even for lower-risk buildings, the building owner's fire risk assessment obligations under the Regulatory Reform (Fire Safety) Order 2005 typically require regular smoke system verification.

Early engagement recommended

Have a smoke shaft to test?
Talk to us early.

Engaging us during the construction phase — not at practical completion — gives you the best chance of a first-time pass and avoids delays to handover.

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