Knowledge article
Emergency Lighting Annual Duration Testing
The annual emergency lighting test discharges the batteries for their full rated duration (commonly 3 hours) to confirm the system lasts the required period.
The annual duration test is the most important emergency lighting check of the year. It confirms the system will keep working for its full rated duration — commonly three hours — not just for the moment the mains fails.
How it differs from the monthly test
A monthly test proves each luminaire illuminates. The annual test proves the batteries have the capacity to run the lighting for the whole required period. The supply is disconnected for the full rated duration and the fittings are checked to confirm they remain adequately lit throughout.
What it reveals
- Weak or ageing batteries that light up but fail before the duration is complete.
- Luminaires that dim prematurely.
- Any fitting that fails to sustain output.
Timing and aftercare
Because the test fully discharges the batteries, plan it for a time when the building can tolerate a period with recharging batteries afterwards (a common approach is out of hours). Record the result in the logbook and replace any failed batteries or luminaires. See also common defects and remedial works.
Frequently asked questions
Why is a full-duration test needed once a year?
A brief monthly test only proves the luminaires light up. The annual full-duration test proves the batteries can actually sustain the lighting for the whole rated period (commonly three hours) — the time people may need to evacuate and the building to be made safe.
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Emergency Lighting Testing
Function and duration testing of emergency lighting to support BS 5266 good practice.
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Standard explained
BS 5266 Overview: Emergency Lighting Standard
BS 5266 is the UK code of practice for emergency lighting — covering design, installation and maintenance so illumination is provided when the normal supply fails.
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Common Emergency Lighting Defects
Common emergency lighting defects include failed batteries, faulty luminaires, missing coverage, no logbook and fittings that light up but fail the duration test.
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Emergency Lighting Explained
Emergency lighting provides illumination automatically when the normal supply fails, helping people evacuate safely — governed by BS 5266.
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Escape Route Lighting Explained
Escape route lighting illuminates corridors, stairways and exits when the supply fails, so occupants can identify and use escape routes safely under BS 5266.
Learn moreThis article provides general guidance and distinguishes legislation, British Standards and good practice. It is not legal advice. Always confirm the specific duties applying to your property and tenure.