Testing a domestic smoke alarm takes a few seconds and most people do it wrong in one specific way: they test each unit separately. The single most valuable thing a weekly test can prove is that the units are interlinked, and that is only proved by pressing one button and listening for the rest of the house.
What the button proves
It confirms the sounder works, the power is present and the electronics are functioning. On most modern devices it also runs a check of the sensing circuit. What it does not do is put smoke into the chamber, so it does not prove that the chamber is clean or that the device would respond to a real fire. That is what periodic cleaning and end of life replacement are for.
Testing an interlinked set
Press and hold the button on one unit until it sounds, and have somebody confirm that every other unit in the property sounds too. Rotate which unit is used each week so that every button and every radio link is proved over time. A unit that sounds on its own but does not trigger the others has lost its interlink, which is the failure that matters most and is invisible if each unit is tested alone.
What the button does not cover
Dust and insects in an optical chamber, which cause both missed detection and nuisance alarms, and which are dealt with by vacuuming the outside of the unit as the manufacturer directs. Age, because the sensing element degrades over roughly a decade whatever the button says. Siting, which the test cannot comment on at all.
Replacement, which is the part most often missed
Every alarm carries a manufacture date, usually on the back, and a stated life from that date rather than from installation. An alarm bought cheaply and fitted three years later has already used part of its life. Writing the replacement year on the unit with a marker at installation is the simplest way to make this visible.
Questions people ask about how to test smoke alarm uk
How often should the test button be pressed?
Weekly is the standard advice, and it takes seconds. Monthly is better than not at all, and neither substitutes for replacing the unit at the end of its life.
Should real smoke be used to test an alarm?
No. Aerosol test sprays exist for professional use on systems; for domestic alarms the button is the test and the manufacturer's cleaning instructions cover the rest.
What if one unit will not sound?
Replace it rather than trying to repair it, and check the interlink afterwards by testing a different unit.