Five to seven months is a safety margin, not a new service interval

When BS 5839-1:2025 replaced the 2017 edition on 30 April 2025, one change got more attention than most: the service interval.

Under the old wording, the gap between services should not exceed six months. The new edition keeps six months as the expected interval, but a service can now take place any time between five and seven months after the previous one. Later than seven months is non-compliant.

It is a sensible change. Schedules slip for real reasons: a customer cancels, an engineer is off sick, a site cannot give access. The old rule turned a two-week delay into a compliance problem.

But there is a way to misuse it, and we are already seeing it.

The drift #

If a scheduler knows they have until month seven, some visits will be booked at month seven. Then the next visit is counted from that date. Then the next. Nobody decides to do it. It just happens when the schedule is busy.

Here is what drift does over three years. At six months, a system gets six services. At seven months, it gets about five.

That is one fewer visit per system every three years. If the customer is paying for two visits a year, they are now getting less than they paid for. If you are paid per visit, you are doing less work and earning less from a contract you already won. Either way, someone notices eventually.

The other problem with booking at the limit #

A service booked at seven months has no margin left. If that visit is cancelled, there is no legal room to reschedule. The system goes out of compliance, and the next audit sample might be that site.

The extra month only protects you if you have not already used it.

How to use the window properly #

Book to six months. Always. Treat the target as six months from the last completed service.

Use month seven only for a reason. A cancellation, an access problem, sickness. Record the reason against the visit.

Count from the actual service date. The next window runs from the date the last service was completed, not the date it was due.

Alert well before the limit. A warning 30 days before month seven gives you room to act. A warning on the day does not.

Track it per system. One site can have several systems with different service dates. A single site date hides the one that is about to go over.

Two more things every visit should now include #

The 2025 edition also expects each service to include checking and adjusting the panel clock, and verifying that the zone chart on site is correct. Clocks drift after power cuts and clock changes, and an out-of-date zone chart slows down anyone responding to an alarm. Both take minutes. Put them on the visit checklist so they are never skipped.

The short version #

The new window is there to absorb real problems. Book to six, keep seven for emergencies, and make sure your scheduling system can tell the difference.

Source: Fire Industry Association, Guide to the changes in BS 5839-1:2025 (https://www.fia.uk.com/static/77c28e9f-486e-4b96-a82e4bb37f4f3882/Guide-to-the-changes-in-BS-5839-1-2025.pdf).