How to Install Smoke and Carbon Monoxide Detectors

In this video, Scott Caron, master electrician for Ask This Old House, wires an old house with new smoke and carbon monoxide detectors.

Steps for Installing Smoke & Carbon Monoxide Detectors

1. Mark the location of each smoke detector on the ceiling.
2. Use a drill and long, stiff wire to bore a small-diameter hole through the ceiling and into the attic.
3. Go into the attic and check for obstructions around the small holes. If necessary, use a circular saw to cut open the attic floor.
4. At each smoke detector location, use a drill and a 4-inch-diameter hole saw with dust shield to cut a hole through the ceiling for a round old-work electrical box.
5. Run nonmetallic electrical cable from an existing outlet in the attic to each of the smoke detector locations.
6. Cut the cable and pull it through an old-work electrical box. Push the box into the ceiling hole and tighten the screws to lock the box to the ceiling. Repeat for each ceiling hole.
7. Screw the smoke detector’s mounting plate to the box, then make the wire connections: black to black, white to white, red to orange.
8. Gently tuck the wires into the box, then twist and lock the smoke detector onto the mounting plate.
9. Install a combination smoke and carbon monoxide detector on each level of the home and within 10 feet of the bedrooms.
10. Pull a new electrical cable down from the attic into the basement.
11. In the basement, install a standard hardwired combination smoke and carbon monoxide detector, and a two-piece wireless smoke and carbon monoxide detector. Mount the battery-powered wireless half of the detector on the first-floor ceiling.
12. Make the final wire connections in the attic, then test each detector to make sure all of them are operating properly.