Replace smoke detectors

Replace smoke detectors that are 10+ years old or malfunctioning to ensure your family's protection.

Why it matters#

Smoke detector sensors degrade over time. A 10-year-old detector may not respond quickly—or at all—when it matters most. New detectors are inexpensive insurance.

What you'll need#

Tools#

• Step stool or ladder
• Screwdriver (Phillips and flathead)
• Drill (if mounting plate needs new holes)

Materials#

• New smoke detector (same type: battery or hardwired)
• Batteries (if not included)
• Mounting screws (usually included)

Steps#

1. Check the manufacturing date#

Find the date on the back or side of each detector. Replace any detector that's 10+ years old.

2. Buy the correct replacement type#

Match the power type (battery-only or hardwired). Dual-sensor detectors are recommended for best protection.

3. Remove the old detector#

Twist counter-clockwise to remove from mounting plate. For hardwired units, squeeze the wire connector sides and pull to disconnect.

4. Check the mounting plate#

If your new detector is the same brand, the existing plate may work. If not, unscrew the old plate.

5. Install new mounting plate (if needed)#

Hold the plate against the ceiling, mark screw holes, and secure with provided screws.

6. Connect wires (hardwired only)#

Match wire colors and connect the plug from the new detector to the house wiring.

7. Install battery#

Insert the battery (if not pre-installed), ensuring correct orientation.

8. Attach detector to mounting plate#

Align the detector with the plate and twist clockwise until it locks in place.

9. Test the detector#

Press and hold the test button until the alarm sounds. For interconnected systems, all detectors should alarm together.

Pro tips#

• Replace all detectors at once if they're the same age
• Consider combination smoke/CO detectors
• Write the installation date on the new detector

Warnings#

• Never paint over a smoke detector—paint blocks sensors
• For hardwired systems, turn off the circuit breaker first

When to call a pro#

Call an electrician if you're uncomfortable with hardwired connections, want to add detectors to an interconnected system, or if existing wiring appears damaged.