Emergency lighting is tested on two cycles that answer different questions. A short monthly function test asks whether each luminaire still comes on when the mains is cut. An annual full duration test asks whether it stays on for the whole period it was designed for, which is the thing that actually fails as batteries age.
The monthly flick test: a short function test
The supply to each luminaire is interrupted briefly, usually with a key switch or a test facility, and every unit is observed to come on. It is kept short deliberately, because a long test drains batteries that then need many hours to recharge, leaving the building with reduced cover in the meantime. The point is to catch failed lamps, failed drivers and units somebody has isolated.
The annual emergency light test at full duration
Once a year the system is run for its full rated duration, commonly three hours, and every luminaire is checked at the end rather than at the start. Batteries lose capacity gradually, so a unit that lights for ten seconds can be dark after ninety minutes, and only the full duration test finds that. It is the test that produces most of the remedial work and the one most often skipped.
Timing it sensibly
After a full duration test the batteries are flat and the system offers little protection until they recharge, which takes many hours. So the test is scheduled when the building can tolerate that, typically at the start of a closed period rather than the end of a working day, and the recharge time is treated as part of the exercise rather than as an afterthought.
Self testing systems
Automatic test systems carry out the function and duration tests on their own schedule and report failures to a panel or a software interface. They remove the labour and the human error and they still need somebody to read the report and act on it. A self testing system with nobody reading its output is a more expensive version of not testing at all.
Other questions people ask
What is an emergency lighting flick test?
The monthly function test, named after the way it is done: a fishtail key in a test switch near the fuse board or beside the light switches is turned to cut the mains to the circuit for just long enough to see every emergency lamp come on, then turned back. HM Government's fire safety guide sets it beside a daily visual check of any central controls and an annual full discharge test.
How often should emergency lighting be tested in the UK?
The common regime is a short monthly function test of every luminaire plus an annual test at full rated duration. The intervals come from the relevant British Standard and are adopted through the fire risk assessment.
What is a 3 hour emergency lighting test?
The annual full duration test on a system rated for three hours. Every luminaire must still be lit at the end of the period, not just at the start.
Why test at the start of a closed period?
Because the batteries are flat afterwards and take many hours to recharge, during which the building has reduced emergency lighting cover.
What does an emergency light service visit include?
On a monthly visit, the short function test of every luminaire and the log entry that records it. On the annual visit, the full duration test with every luminaire checked at the end of the period rather than the start, plus the lamps, batteries and drivers that test condemns. Ask which of the two a quoted service covers, because a contract priced on monthly visits alone leaves out the test that finds the failures.
What is the required emergency lighting testing frequency?
Monthly and annually, with a third interval that catches people out. Monthly is a short function test of every luminaire, usually by operating the test key or switch, walking the route and logging what illuminated. Annually is the full rated duration test, three hours for most systems, followed by a recharge period, and it is the one that proves the batteries. The third is the design's own: a system with a central battery has its own maintenance schedule for the cells, and any alteration to the layout means the lighting design is re checked, because a new partition can leave a route unlit.