AOV systems in UK buildings must be maintained and tested at regular intervals under the Regulatory Reform (Fire Safety) Order 2005, BS 9999, and BS 9991. The minimum requirement is a weekly visual check, a monthly functional test, a six-monthly full system test, and an annual inspection by a competent engineer. Battery backup units must be tested annually and batteries replaced every three to five years.

Legal Basis for AOV Maintenance

The Regulatory Reform (Fire Safety) Order 2005 (RRO) requires the Responsible Person of any non-domestic premises — and common areas of residential buildings — to ensure that fire precautions, including fire safety equipment, are maintained in efficient working order and good repair. An AOV system is fire safety equipment. Failure to maintain it is a criminal offence that can result in enforcement action by the local fire and rescue service.

For residential buildings over 18 m, the Building Safety Act 2022 adds further obligations for the Accountable Person to maintain safety systems and report to the Building Safety Regulator.

Recommended Maintenance Frequencies

Weekly Check

The building manager or caretaker should visually inspect the AOV control panel once a week. The check takes less than a minute: confirm that the mains power indicator is on, that no fault LEDs are illuminated, and that the panel display shows a normal standby condition. Log the check in the fire safety log.

Monthly Functional Test

A functional test should be conducted monthly to confirm that the system responds correctly to a detector alarm. This involves activating a detector using a test aerosol (or, on addressable systems, using the panel test function) and confirming that the correct vents open and that any associated alarm signals are transmitted. All vents should be tested in rotation over successive monthly tests so that the full system is exercised over a three- to six-month cycle.

Six-Monthly Full System Test

A more thorough test should be conducted every six months by a competent engineer. This includes:

  • Smoke testing of all detectors in every zone
  • Full activation of all actuators and vents
  • Confirmation that all vents achieve their required open position
  • Test of fire service override switches
  • Test of mains failure: disconnect mains and confirm system operates on battery backup
  • Inspection of all wiring and connections for signs of damage or deterioration

Annual Inspection

Once a year, a full inspection and service should be carried out. This is in addition to the six-monthly test and includes:

  • All six-monthly test items
  • Battery capacity test: measure the battery terminal voltage under load and compare against the manufacturer’s specifications to confirm the battery can still deliver the required standby duration
  • Actuator lubrication and mechanical inspection
  • Vent seal and hardware inspection
  • Review of all maintenance records and confirmation that the system matches the as-installed drawings

Battery Replacement

Sealed lead-acid batteries used in AOV battery backup units have a typical design life of three to five years. Capacity degrades over time, and an aged battery may not provide the required 72-hour standby period even if the battery voltage appears normal on a simple voltage check. A proper capacity test under load is the only reliable method of assessing battery condition.

AOV Direct recommends replacing batteries every four years as a planned maintenance measure, regardless of measured condition, to ensure reliable system performance. Replacement batteries must be of the correct type and capacity for the BBU — do not substitute a different chemistry or a lower Ah rating.

Batteries should be disposed of at an approved recycling facility. Lead-acid batteries are classified as hazardous waste and must not be placed in general waste or landfill.

Record Keeping

All tests, inspections, and maintenance activities must be recorded in the building’s fire safety log. Records should include:

  • Date and time of each test
  • Name and competence of the person conducting the test
  • What was tested and the outcome
  • Any defects found and the remedial action taken
  • Battery test results and replacement dates

For higher-risk buildings (over 18 m), this information forms part of the Golden Thread of building information and must be stored digitally and kept up to date.

Who Can Carry Out AOV Maintenance?

Weekly visual checks can be carried out by the building manager or caretaker with minimal training. Monthly functional tests and six-monthly/annual full tests should be conducted by a competent engineer with specific knowledge of smoke control systems. Competence can be demonstrated by relevant qualifications (e.g. BAFE SP207 scheme membership) or by documented training and experience.

Spare Parts and Replacement Components

AOV Direct supplies replacement batteries, actuators, smoke detectors, and control panel spares for AOV systems. Holding a spare battery and a replacement detector on site ensures that any fault identified during a test can be remediated promptly without leaving the system in a degraded state. View battery backup replacements or contact us for help identifying the correct replacement part for your system.

Frequently Asked Questions

What happens if my AOV system fails its maintenance test?

Any defect identified during a maintenance test must be repaired promptly. If the system cannot be made operational quickly, the Responsible Person must put interim fire safety measures in place — for example, a waking watch in residential buildings — and notify the fire and rescue service if required. Do not simply log the failure and move on without remediation.

Is there a British Standard for AOV maintenance?

BS 9999 and BS 9991 both include guidance on testing and maintenance of smoke ventilation systems. BS EN 12101-6 covers testing of smoke control systems. The SHEVTEC guide produced by the Smoke Control Association provides practical guidance on maintenance procedures aligned with these standards.

Do I need a specialist contractor for AOV maintenance?

The Responsible Person is not required by statute to use a specialist contractor, but must ensure that whoever conducts the maintenance is competent. In practice, specialist fire protection companies with experience of smoke control systems are the appropriate choice for six-monthly and annual inspections. Membership of a recognised scheme such as BAFE SP207 provides a benchmark for contractor competence.