Replace an expired smoke or carbon-monoxide alarm

Identify the existing alarm and why it is being replaced

Age, alarm type, power source and interconnection matter more than physical appearance.

• • Record the manufacturer, model, manufacture/replace-by date and listed alarm type from the label.
• • Treat an end-of-life indication or failed test as a replacement condition, not something to silence indefinitely.
• • Do not remove required protection from service without installing the appropriate replacement.

Verify before moving on: The alarm purpose, power source and replacement reason are understood.

Safety: If an alarm is sounding for a possible real smoke/CO emergency, respond to the hazard first rather than troubleshooting the device. Do not disable required alarms to stop nuisance events.

Choose a replacement that preserves the safety function

Smoke, CO and combination alarms are not interchangeable merely because they fit the same ceiling location.

• • Match the needed smoke/CO function and listed use for the location.
• • Preserve hardwired/interconnected functionality when the existing system requires it.
• • Follow current manufacturer/local placement and replacement instructions rather than relying on the old mounting pattern alone.

Verify before moving on: The replacement is appropriate for the required detection function, power source and interconnection.

Make hardwired replacement electrically safe

Current type: battery-only smoke alarm. Battery-only units do not require opening building wiring; hardwired units do.

• • Remove the battery-only/plug-in alarm according to its mounting instructions.
• • Keep mounting hardware organized and do not disturb unrelated wiring.
• • Stop for damaged wiring, unknown extra conductors or a system that does not match the replacement instructions.

Verify before moving on: The old alarm is safely removed and any electrical connection method is understood.

Safety: Hardwired alarm conductors are building wiring. Do not work energized or improvise non-listed connector adaptations.

Install, date and test the replacement

A mounted alarm is not complete until its self-test and interconnection behavior are proven.

• • Install the mounting plate and alarm according to the current instructions.
• • Install/activate the specified battery or sealed-power activation feature.
• • Mark the installation/replacement date if the manufacturer instructions provide for it.
• • Run the built-in test and, for interconnected systems, confirm the expected linked alarms respond.

Verify before moving on: The replacement passes its test and any required interconnection works.

Restore full protection and document the replacement

Keeping the model/date makes future end-of-life replacement easier.

• • Restore power to hardwired alarms.
• • Confirm no trouble/chirp indication remains after the manufacturer-defined startup period.
• • Save the model, date and replacement interval with home records and recycle/dispose of the old unit according to local/manufacturer guidance.

Verify before moving on: Required alarm coverage is restored with a working, documented replacement.