Commissioning is the stage that turns a newly installed fire alarm into a working, certified life safety system. It is where every device is tested, every function is proved and every document you need is handed over. If you are having a new system installed, or an existing one extended, this guide explains what commissioning involves under BS 5839-1:2025, what you should expect from your engineer and what you should receive at the end.
What fire alarm commissioning is
BS 5839-1 splits every fire alarm project into four stages: design, installation, commissioning and handover. Each stage has its own certificate. Commissioning is the point where someone checks that the installed system matches the design, works exactly as intended and is ready to protect your building.
Commissioning is not the same as installation
Installation is the physical work of running cables and fixing devices. The installer tests their own wiring and certifies it. Commissioning comes afterwards and takes a step back. The commissioning engineer looks at the whole system, tests every function and confirms it does what the design says it should. A system can be installed neatly and still fail commissioning because a detector is the wrong type for the room or a door does not release when it should.
Who should commission your system
Commissioning must be carried out by a competent person with a thorough knowledge of fire alarm systems and of BS 5839-1. In practice, that means a specialist fire alarm engineer rather than a general electrician. Third party certification such as BAFE SP203-1 gives you independent evidence that the company commissioning your system is competent.
Checks before the system goes live
Before testing anything, your commissioning engineer should walk the building with the design drawings in hand.
Inspecting the installation against the design
- Every detector, call point and sounder is in the right place and is the right type for the room.
- Cables are the correct fire resisting type, properly supported and kept apart from other services.
- Manual call points are at the right height and no further than 45 metres travel from anyone.
- The control panel is in an agreed location, usually near the main entrance used by the fire service.
- An up to date zone plan is displayed beside the panel.
Reviewing the installer’s records
The engineer should also check the installer’s test results, such as cable insulation and earth continuity readings, and confirm the installation certificate is complete. Any changes made on site during installation need to be reflected in the drawings before handover.
Testing every device and function
This is the core of commissioning. Unlike a routine service, where devices are tested across a year, commissioning tests everything at once.
Detectors, call points and sounders
Every detector is tested with the right test equipment, whether smoke, heat, carbon monoxide or multi sensor. Every call point is operated. For each one, the engineer confirms the panel shows the correct zone and location text, so the fire service knows exactly where to go. On multi sensor detectors with several operating modes, BS 5839-1:2025 now requires the chosen setting to be recorded.
Cause and effect and connected systems
Your fire alarm rarely works alone. It may release door holders, return lifts to the ground floor, open smoke vents, shut down ventilation or signal an alarm receiving centre. The engineer tests each of these against your cause and effect document, which every system now needs under the 2025 edition. Signals to an alarm receiving centre should arrive within 90 seconds for life safety systems, so this timing is checked too.
Sound levels and power supplies
Measuring alarm sound levels
An alarm only works if people hear it. The engineer measures sound levels across the building with a calibrated meter. BS 5839-1 generally calls for at least 65 dB(A) throughout the building, and at least 5 dB(A) above any background noise likely to last more than 30 seconds. Where people sleep, the level should reach 75 dB(A) at the bedhead with the doors closed. Where sounders cannot work, such as in very noisy areas or for people with hearing loss, visual alarm devices are checked too.
Batteries and standby power
If the mains fails, your system runs on batteries. The engineer checks the battery size against a standby calculation, typically 24 hours of standby plus 30 minutes of alarm, and tests the charger. Under the 2025 edition, batteries should be labelled with their installation date so you know when they are due for replacement.
Handover: what you should receive
Commissioning ends with handover to you. Do not accept a system until you have everything below.
Your certificates and documents
- Design, installation and commissioning certificates, plus a certificate for you to sign confirming you accept the system.
- As fitted drawings showing every device and cable route.
- A zone plan displayed beside the panel.
- A cause and effect matrix or written description.
- A logbook, with any agreed variations from the standard already recorded.
- Operating and maintenance instructions, including the settings chosen for any multi sensor detectors.
Training and false alarm advice
Your engineer should show you how to use the panel, silence and reset alarms and carry out the weekly test. Under the 2025 edition, they should also explain the different types of false alarm and how to investigate them. Calum Mansell IEng MIET, writing in the IET’s Wiring Matters in November 2025, notes that users must be told to investigate false alarms “at every false alarm occurrence”. Our guide on how often a fire alarm should be serviced explains what happens after handover.
Why proper commissioning matters
False alarms start at commissioning
In the year ending March 2026, fire and rescue services in England attended 172,247 false alarms caused by fire alarm equipment, according to Home Office figures. Many of these trace back to decisions made when the system was new, such as a smoke detector placed next to a kitchen or a multi sensor left on the wrong setting. Thorough commissioning catches these problems before they cost you call outs, disruption and lost trust from staff.
How we commission your system
Advantage Technical Services is BAFE SP203-1 accredited and commissions every system to BS 5839-1:2025. We test every device, prove every interface and hand over a complete, organised set of documents, so you start with a system you can rely on and paperwork that stands up to any inspection. If you are an electrical contractor installing the system yourself, we can design, supply and commission it for you. See our commercial fire alarm services, read what changed in BS 5839-1:2025 or get in touch to discuss your project.
Frequently asked questions
What is fire alarm commissioning?
It is the process of checking a newly installed fire alarm against its design, testing every device and function, and handing the system over with full certification and documents.
Who can commission a fire alarm system?
A competent person with thorough knowledge of fire alarm systems and BS 5839-1. Choosing a third party certificated company, such as one with BAFE SP203-1, gives you independent proof of competence.
How long does commissioning take?
It depends on the size of the system and how many interfaces it has. A small system can be commissioned in a day. A large building with lifts, door holders and smoke control takes longer.
What certificates should I receive?
Design, installation and commissioning certificates, plus a certificate you sign at handover to confirm you accept the system. Keep all of them with your logbook.
What happens if faults are found during commissioning?
They should be put right before handover. Anything that cannot be fixed, and any agreed departure from the standard, must be recorded in your logbook and on the certificates.
Does an extension or modification need commissioning?
Yes. The new work must be tested and certified with an extension or modification certificate, and it must follow BS 5839-1:2025 even if the rest of the system was built to an older edition.
No responses yet