Automatic Opening Vents (AOVs) are life safety equipment. When a fire breaks out, they are expected to open - every time, without failure. But in practice, many AOV systems fall short of that expectation because maintenance has been treated as an afterthought rather than a fundamental part of the system’s lifecycle.
This guide is written for building managers and facilities teams responsible for smoke ventilation systems. It covers what AOV maintenance actually involves, what the regulations require, and how to structure a maintenance programme that gives your system - and your building’s occupants - the best protection.
Is AOV Maintenance a Legal Requirement in the UK?
AOV systems form part of a building’s fire safety strategy. Under the Regulatory Reform (Fire Safety) Order 2005, the responsible person for a building is legally required to maintain fire safety measures in efficient working order. Smoke ventilation systems form part of the fire safety measures that must be maintained in efficient working order.
The Smoke Control Association (SCA) Guidance on the Maintenance of Smoke Control Equipment provides detailed best practice for maintenance of these systems. The guidance aligns with BS 7346 Part 8, which sets out requirements for the functional testing of smoke control systems.
Failure to maintain an AOV system is not only a safety risk - it can also invalidate insurance, create regulatory exposure, and in serious cases, lead to prosecution following a fire event.
What Does an AOV System Consist Of?
Before planning a maintenance programme, it helps to understand the full scope of what a typical AOV system includes:
- AOV vents and windows - the physical vent units that open to release smoke
- Actuators - electric or pneumatic devices that open and close the vents
- Smoke control panels - the control equipment that manages system activation
- Override switches - firefighter controls, typically located at building entrances
- Detection interfaces - connections to the fire alarm system that trigger the AOVs
- Power supplies - mains and battery backup power arrangements
- Smoke shafts and ductwork - the ventilation pathways that direct smoke to the outside
Each of these components requires inspection and testing. A maintenance regime that checks only the vents and ignores the control panel, detection interfaces, or backup power is not adequate.
What Are the Three Tiers of AOV Maintenance?
BS 7346-8 sets the core inspection cadence: weekly visual checks, quarterly full actuation simulation, and an annual competent-person comprehensive service. SCA guidance commonly supplements this with a six-monthly intermediate inspection by a competent specialist. Here is what each tier should involve.
Weekly Checks
Weekly checks are typically simple visual or functional checks that a facilities team member can carry out without specialist knowledge:
- Check the smoke control panel for any active faults or warnings
- Confirm fault indicators are not illuminated
- Check that override switches are accessible and undamaged
- Log any observations in the system logbook
These checks take only a few minutes but provide an early warning of developing faults before they compromise system performance.
Six-Monthly Inspections
Six-monthly inspections should be carried out by a competent smoke control specialist. These inspections go beyond visual checks and include functional testing:
- Test AOV vents open and close correctly
- Verify actuator travel and opening times against design specification
- Check battery backup systems are charged and functioning
- Test firefighter override switches operate correctly
- Inspect cables and wiring for damage
- Check control panel programming remains correct
- Review the cause and effect matrix for any changes
- Update the system logbook
Six-monthly inspection is the minimum frequency recommended by the SCA for most buildings. Some buildings with more demanding use profiles or larger systems may require more frequent inspections.
Annual Inspections
Annual inspections are more thorough and should include everything in the six-monthly programme plus:
- Full system test against the cause and effect matrix
- Verification of fire alarm interface and signal sequences
- Smoke shaft inspection where applicable
- Lubrication of actuator mechanisms
- Review of commissioning records and design documentation
- Assessment of any building changes that may affect system performance
- Issue of a formal inspection report
An annual inspection report provides documented evidence of compliance. This documentation is increasingly important during building safety inspections under the Building Safety Act 2022 regime.
What Are the Most Common AOV Maintenance Failures?
During maintenance inspections across the UK, certain faults recur repeatedly. Understanding these common failures helps building managers know what to watch for.
Dead batteries in backup power systems. AOV systems are required to operate during power failure. If the battery backup is not maintained, the system will fail precisely when it is needed most. Battery condition should be checked and load-tested at every six-monthly inspection.
Actuator drift and mechanical wear. Actuators that have not been exercised regularly can develop stiffness or fail to reach full travel. Over time, seals dry out and mechanisms wear. Regular cycling of the actuators during inspections identifies this before it becomes a critical failure.
Incorrect cause and effect programming. Building changes, refurbishments, or fire alarm upgrades can leave the cause and effect matrix out of step with the actual building configuration. If a new smoke detector is added but the AOV panel is not updated, zones may not activate correctly during a fire.
Override switches left in override mode. Firefighter override switches are occasionally left in a non-automatic position following maintenance or testing by other contractors. This means the system will not respond to fire detection. Override switch position should be checked at every inspection.
Missing or incomplete system logbooks. Without a complete logbook record, it is impossible to confirm that inspections have been carried out, faults have been rectified, or that the system has been maintained continuously. The absence of a logbook is often the first indicator that maintenance has lapsed.
What Should You Expect From a Competent Maintenance Contractor?
The SCA Guidance recommends that maintenance is carried out by engineers who have the necessary competence to work on smoke control systems. This means more than general electrical or mechanical competence - it requires specific knowledge of smoke ventilation systems, BS 7346, and the requirements of the individual system’s fire strategy.
When engaging a maintenance contractor, you should expect:
- Evidence of relevant competence (training by the smoke control manufacturer or SMR01 registration are the recognised paths for smoke control maintenance)
- Pre-visit review of the system fire strategy and cause and effect matrix
- Structured inspection reports with fault identification and remediation advice
- Updated logbook entries following every visit
- Clear communication of any safety-critical faults identified during inspection
If a maintenance contractor cannot provide a structured inspection report that references the system’s design requirements, that is a significant warning sign.
What Records Should an AOV System Logbook Contain?
The system logbook is a legal record. It should document:
- Every inspection visit, including date, engineer, and findings
- Any faults identified and the actions taken
- Test results for all system components
- Battery test results
- Any changes made to system programming or components
- Building changes that may affect system performance
The logbook should be kept in or near the smoke control panel and made available to any inspecting authority on request. Under the Building Safety Act 2022, higher-risk buildings are subject to more extensive documentation requirements, with records potentially needing to be maintained for the life of the building.
How Do Building Changes Affect AOV System Performance?
One of the most overlooked aspects of AOV maintenance is the impact of building changes on system performance. Refurbishments, changes of use, partition changes, and new detection systems all have the potential to affect how the smoke ventilation system performs.
Before any significant building work, a fire engineer should assess whether the existing smoke ventilation strategy remains valid. If changes are made that affect ventilation paths, vent locations, or the building’s compartmentation strategy, the AOV system may need to be updated and recommissioned.
Building managers should ensure that any principal contractor undertaking work in the building is made aware of the smoke ventilation system and its requirements, and that AOV maintenance contractors are informed of any significant changes following completion of works.
Getting the Right Support
Vent Trade has been supplying and commissioning smoke ventilation equipment since 1988. Our Managing Director chairs the SCA Maintenance Guidance working group - the industry body that sets the standards for AOV system maintenance across the UK.
If you are unsure whether your AOV system’s maintenance programme meets current requirements, or if you have inherited a building with limited documentation about the smoke ventilation system, our technical team can help. We offer maintenance audits, commissioning verifications, and full replacement programmes for systems that have fallen behind.
Call us on 01202 725 485 or email info@vent-trade.co.uk to discuss your requirements.
Sources
Official guidance and standards referenced in this article: