Smoke Alarm Expiry Date and Replacement Schedule for Landlords
A smoke alarm can pass a push-button test and still be functionally useless. The internal sensor — whether photoelectric, ionisation, or electrochemical — degrades over time, and after a certain point the alarm may sound when you press the button but fail to respond to actual smoke or carbon monoxide. Knowing when your alarms expire is a basic compliance task that too many landlords overlook.
Manufacture Date vs Installation Date
This is the critical distinction. A smoke alarm's sensor lifespan starts from the date it was manufactured (the DOM — date of manufacture), not the date you fitted it to the ceiling. An alarm that sat in its packaging for two years before installation has already consumed two years of its sensor life.
The DOM is typically printed or stamped on the back of the alarm unit. Look for a label showing the month and year of manufacture, or a "replace by" date calculated from the DOM. If no replace-by date is shown, apply the manufacturer's stated lifespan — usually 10 years for smoke alarms and 7 to 10 years for CO alarms.
Typical Lifespans
Smoke alarms: Most domestic smoke alarms carry a 10-year lifespan from DOM. This applies to both battery and mains-powered units. The photoelectric sensor element degrades through normal ageing even in clean air.
Carbon monoxide alarms: Electrochemical CO sensors typically last 7 to 10 years from DOM, depending on the manufacturer. Some premium units offer a 10-year warranty, but many have a 7-year sensor life. The CO sensor depletes through a chemical reaction with ambient gases — it doesn't need to detect an actual CO event to age.
Sealed-battery alarms: On models where the battery and sensor share a 10-year lifespan, the alarm will typically signal end of life when that period is reached. Follow the manufacturer's instructions on whether to replace the complete unit or service its battery.
Why the Push-Button Test Isn't Enough
Pressing the test button confirms that the sounder works and the battery has charge. It does not test the sensor's ability to detect smoke particles or CO gas. An expired alarm with a working battery will beep on demand but may never activate in an actual emergency.
This is the scenario landlords underestimate. A council inspector or tribunal judge won't accept "it beeped when I pressed the button" as evidence of a functioning alarm if the unit is three years past its manufacturer-stated expiry.
Free Download
Get the England Smoke and CO Alarms Checklist
Everything in this article as a printable checklist — plus action plans and reference guides you can start using today.
Building a Replacement Schedule
For every alarm in a rental property, record three dates:
- Date of manufacture (DOM) — read from the unit's back label
- Date of installation — when you fitted it to the property
- Replace-by date — DOM plus the manufacturer's stated lifespan (e.g., DOM January 2020 + 10 years = replace by January 2030)
Check these dates during your tenancy-start alarm test and add them to your compliance record. When an alarm approaches its replace-by date, plan the swap proactively — don't wait for the end-of-life chirp, which will annoy your tenant and create an avoidable fault report.
Multiple Properties and Tracking
If you manage several rental properties, alarm replacement dates can easily slip through the cracks. A simple spreadsheet tracking property, alarm location, DOM, and replace-by date — with calendar reminders at the 9-year mark — prevents surprises. Batch-purchasing alarms means batch-replacing them, which simplifies logistics.
For sealed battery units, the whole-unit replacement cycle is clean: buy the replacement, remove the old unit (note the DOM of the new one), fit the new unit, and test it. No battery swaps, no compatibility issues. Budget approximately £15–£25 per smoke alarm and £20–£30 per CO alarm every 10 years — a negligible ongoing cost.
What If a Tenant Finds an Expired Alarm?
If a tenant discovers that an alarm has passed its expiry date and reports it, the 2022 amendments require you to repair or replace it "as soon as reasonably practicable." The regulations set no fixed 24-to-48-hour deadline. Acknowledge the report in writing, arrange replacement as soon as reasonably practicable, perform a push-button test on the new unit, and log the replacement.
An expired alarm that remains installed after a tenant report creates the same enforcement exposure as a missing alarm — the council can serve a Remedial Notice and, if compliance doesn't follow within 28 days, a Penalty Charge Notice.
The alarm compliance guide includes a hardware lifecycle tracker template for logging DOM, installation, and replacement dates across every alarm in a property — so the replace-by date never catches you off guard.
Get Your Free England Smoke and CO Alarms Checklist
Download the England Smoke and CO Alarms Checklist — a printable guide with checklists, scripts, and action plans you can start using today.