Guide · updated September 2026

BS 5839-1:2025: what changes on your certificates

BS 5839-1:2025 replaced the 2017 edition in 2025. Most of the recommendations are the same, but the numbering changed throughout, so any certificate that quotes 2017 clause numbers is out of date. These are the changes that show up on inspection, servicing and modification paperwork.

Summary in our own words from public sources, chiefly the FIA's free "Guide to the changes in BS 5839-1:2025" (v1, June 2025). Check the standard itself before relying on a clause.

1. New numbering

Subclauses are numbered (for example 21.2.4) instead of lettered. Inspection and servicing is now clause 43 (it was 45 in 2017). The model certificates are in Annex G and the logbook in Annex H (it was Annex F).

2. Service interval: 5 to 7 months is acceptable

Visits should still be about every 6 months, with the date of acceptance as the datum, but one visit anywhere between 5 and 7 months after the last one is acceptable (43.2.1). The 2017 wording treated anything over 6 months as non-compliant.

3. New checks at every visit

• Check and correct the CIE clock (important with day/night modes).
• Where the system signals an ARC, confirm each signal type (fire, fault) arrives.
• Tell premises management which areas are disabled while you test, and keep that to a minimum.

4. New at the 12-monthly visit

• Functionally test smoke detectors in ventilation ducts.
• Check that the zone shown at the CIE is the zone you tested and matches the zone plan.

5. False-alarm rate (Annex F)

A new annex gives the calculation: false alarms in the last 12 months per 100 automatic detectors. Above 4 per 100 detectors per year suggests a preliminary investigation; for systems with more than 40 detectors, an average above 5 suggests an in-depth one (clause 31). FireCerts works the figure out as you type.

6. Remote access and cyber security (43.4)

Where the CIE can be reached remotely, access points should be physically secured, remote connections authenticated, and a risk assessment done before remote read, control or write actions.

7. Extension or modification certificate (Section 7)

The modification certificate becomes an "extension or modification" certificate. Updating CIE firmware counts as a modification. Redundant devices should be removed or clearly labelled as not in use.

8. Handover: cause and effect

Documentation handed over should include a cause-and-effect matrix or a plain description of it. Users should be told how to investigate every false alarm (29.6).

9. Battery calculation (Annex E)

Annex E adds T2, the total battery alarm period in hours, in line with the rest of the BS 5839 series.