Test and replace smoke alarm batteries

Test every smoke alarm, replace flat batteries, then log the date and reset your monthly reminder.

SA-01Gather your tools and check each alarm's battery typeGet your steps and a torch. Look inside the cover of each alarm: it will say 9V battery, AA battery, or 'sealed unit, non-replaceable battery'. If a cable runs into the base plate, it's mains-powered with a small backup battery inside, rather than fully battery-only.

1 each · Torch

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1 each · Marker pen or sticky labels

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SA-02Test every alarm before touching the batteryPress and hold the test button for about 5 seconds until you hear a loud, sharp test tone. This checks the horn and electronics, not just the battery. A single soft chirp every 30-60 seconds means a low battery; total silence means a bigger fault. If you're a tenant, your landlord must keep working smoke alarms fitted and fix a reported fault.

RULES

KNOW THE RULES

Smoke and Carbon Monoxide Alarm (England) Regulations 2015: landlords must ensure a working smoke alarm on every storey used as living accommodation, and repair or replace one once told it's faulty.

SA-03Isolate the power before opening a mains-powered alarmIf your alarm has a cable feeding into its ceiling base plate, it's mains-powered. Turn off the lighting circuit at the consumer unit before twisting the alarm off the base plate, because this exposes bare mains terminals inside. Skip this entirely for a plain battery-only alarm that simply unclips by hand.

SA-04Remove the old battery or unitTwist the alarm anti-clockwise off its base plate, or open the battery flap on a plug-in type. Slide out the old 9V or AA batteries. If the label says 'sealed unit, non-replaceable battery', don't try to open it — buy a whole new alarm instead, since these have a fixed 10-year life and get swapped as one piece.

1 each · Replacement sealed 10-year smoke alarm

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SA-05Fit the new battery or new alarmPush in a fresh 9V or AA battery, matching the + and - marks in the compartment. For a sealed alarm, clip the new unit straight onto the existing ceiling base plate. Write today's date on a sticky label on the case so you know when it was last done.

1 each · 9V alkaline battery

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1 pack · AA batteries (pack of 4)

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SA-06Refit the alarm and retestTwist the alarm back onto its base plate until it clicks flush against the ceiling. Switch the lighting circuit back on at the consumer unit if you turned it off earlier. Press the test button again and check for the same loud test tone as before.

SA-07Clean the alarm and the area around itWipe dust off the case with a dry cloth, and run a vacuum brush attachment over the vents at the sides — a dusty vent is a common cause of weak tones or false alarms. Refit the cover properly and fold your steps away.

1 each · Vacuum brush attachment or soft cloth

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SA-08Dispose of old batteries and set a reminderTake old batteries to a recycling point at a supermarket or household waste site — don't bin them with general rubbish. Set a monthly reminder to press the test button, and a yearly one to swap batteries, or sooner if you hear a low-battery chirp.

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