AOV Smoke Shaft Pressure Testing
Fire Safety Compliance for Residential Developments
AOV Smoke Shaft Pressure Testing — Fire Safety Compliance for Residential Developments
The smoke shaft is one of the most critical elements of the fire safety strategy in a multi-storey residential building. Its function, to remove smoke from common escape routes in the event of fire, keeping corridors clear long enough for occupants to escape safely, depends entirely on the shaft structure being sufficiently airtight to maintain the pressures and airflows that the AOV system is designed to generate. If the shaft leaks excessively, the AOV system cannot perform as designed, and the fire safety strategy of the building is compromised at the most fundamental level.
Stansted Environmental Services Ltd provides AOV smoke shaft pressure testing services for residential developers, principal contractors, fire safety engineers, and mechanical services contractors across the United Kingdom. We test the air permeability of completed smoke shaft structures before the AOV system is installed, identifying any areas of leakage whilst access is still straightforward and remediation is inexpensive. Testing at this stage is one of the most cost-effective steps a developer can take, catching a leaky shaft before the AOV goes in costs a fraction of what it costs to find the same problem after commissioning.
What Is AOV Smoke Shaft Pressure Testing?
An AOV smoke shaft pressure test is an air tightness assessment of a completed smoke shaft. The test is carried out using the same UKAS-calibrated blower door equipment used for building air tightness testing, with all shaft openings temporarily sealed and the fan introduced through one of the sealed openings to pressurise and depressurise the shaft to a series of reference pressures.
The airflow data collected at each pressure step is analysed to calculate an air permeability figure for the shaft construction, which is compared against the performance criterion specified by the fire safety engineer or the smoke control system designer. If the result meets the required standard, the test is complete and the AOV system can proceed to installation. If the result does not meet the standard, artificial smoke is introduced into the pressurised shaft and observers positioned at each opening monitor smoke movement to identify the locations of the leakage.
Why Test Before the AOV System Is Installed?
The logic behind pre-installation smoke shaft testing is straightforward. While the shaft is under construction and before the AOV equipment is fitted, every part of the shaft structure is accessible. Gaps at ductwork joints, missing sealant at penetrations, and defective interfaces between the shaft and adjacent construction can all be located and repaired without dismantling any installed systems. The cost of these remedial works at this stage is minimal, typically a few hours of a sealant applicator’s time.
If the same defects are not identified until after the AOV system has been installed and the commissioning engineer cannot achieve the required shaft pressures and airflows, the situation is fundamentally different. Accessing the shaft structure to make remedial repairs will require the removal of AOV dampers, ductwork sections, or control components, depending on where the leakage is located. The cost of AOV removal, remediation, reinstatement, and recommissioning on a high-rise residential scheme can easily run into tens of thousands of pounds, and the programme impact of the delay particularly if the scheme is close to handover is often even more significant. Building Safety Act gateway requirements add further pressure, as fire and smoke control systems must be demonstrated to be functioning correctly before the Building Safety Regulator will grant the Building Completion Certificate for higher-risk buildings.
What the Test Involves in Practice
Before testing commences, all openings to the smoke shaft structure are temporarily sealed. This includes the corridor inlet grille positions on each floor, any lobby damper openings, the roof-level discharge outlet, and any other penetrations through the shaft boundary. The blower door fan is mounted in a temporary frame installed in one of the sealed openings, typically at mid-level of the building depending on access. Internal ventilation within the shaft is sealed off to create a single closed test envelope.
The fan is then operated to pressurise and depressurise the shaft to a series of pressure levels, and the airflow at each level is recorded. The data is processed to calculate the air permeability of the shaft construction. In most cases, this phase of the test takes between two and four hours, depending on the shaft size and access conditions. Where the result meets the required standard, the test is complete. Where the result is outside the required tolerance, artificial smoke, a non-toxic theatrical fog, is injected into the pressurised shaft and observers at each floor level and at roof level monitor for smoke egress through any leakage points. Identified leakage locations are recorded and reported to the contractor for remediation.
Compliance Context — Building Safety Act and BS EN 12101
The importance of smoke shaft testing has increased significantly following the implementation of the Building Safety Act 2022 and the gateway regime administered by the Building Safety Regulator for higher-risk buildings. Under the gateway process, developers and principal contractors must demonstrate to the Regulator that fire safety systems including smoke control have been installed and commissioned correctly before the Building Completion Certificate is granted. A smoke control system that has not been properly tested and verified throughout the construction process is unlikely to satisfy the Regulator’s requirements, and the gateway cannot be passed until all outstanding issues have been resolved.
The design and performance criteria for smoke shaft systems are set out in BS EN 12101 and in the guidance published by the Smoke Control Association. The air permeability criterion for a smoke shaft structure is typically specified by the fire safety engineer based on the system design, and SES works closely with fire safety engineers and smoke control designers to ensure that the testing methodology and acceptance criteria are aligned with the specific requirements of each project.
SES are a multi-disciplined environmental consultancy with a proven track record of providing high quality.
How Much Does Smoke Shaft Pressure Testing Cost?
The cost of smoke shaft pressure testing depends on the number of shafts to be tested, the height and complexity of each shaft, the access conditions, and the travel distance to site. For a single smoke shaft in a medium-rise residential development in the South East of England, testing typically starts from around £600 plus VAT. Multiple shafts on the same visit can be tested at a reduced rate per shaft. Please contact us with details of your scheme for a fixed-price quotation. Remember that this cost is a fraction of what AOV removal and remediation would cost if leakage is discovered at commissioning stage.
Regions We Cover for Smoke Shaft Testing
SES provides smoke shaft pressure testing across London and the South East including Essex, Kent, Surrey, Hertfordshire, and Middlesex as well as the Midlands, the North West, Yorkshire, and all other regions of England and Wales. Contact us to confirm availability and obtain a quotation for your scheme.
Enquire About Smoke Shaft Pressure Testing
Contact SES on 0808 239 2327 or 020 3993 4974, or use our online contact form. Please provide the site address, the number of shafts to be tested, the approximate height of each shaft, and your preferred testing window, and we will respond with a quotation and availability confirmation within twenty-four hours.
