Hard-Wired Smoke Detector Installation

Remove the fuse or trip the circuit breaker, depending on the type of fuse box, to discontinue electricity to the room where you will be installing the smoke detector in place of a lighting fixture. Place a ladder against the wall or beneath the ceiling where the lighting fixture is located.

Remove the bulb or bulbs from the lighting fixture by screwing them counterclockwise -- wear a glove if the light bulb(s) has not been given time to cool down.

Remove the screws from around the lighting fixture with a Phillips screwdriver. Pull the fixture off the wall or ceiling.

Unscrew the nuts from around the twisted pairs of wires connected between the fixture and the electrical junction box inside the cavity that was concealed by the fixture. Place the nuts in your pocket to use later. Untwist the wires from each other. Remove the lighting fixture from the wall or ceiling. Place the fixture aside.

Strip 1/2-inch of insulation off the ends of the three wires attached to the back of the smoke detector -- use a wire strippers to remove the insulation.

Twist the exposed ends of the wires attached to the electrical junction box to the exposed ends of the wires attached to the smoke detector in the following manner: the black wire from the electrical junction box to the black wire from the smoke detector; the white wire from the electrical junction box to the white wire from the smoke detector.

Screw a nut onto each pair of twisted wires. Push the wires inside the cavity in the wall or ceiling. Place the smoke detector over the cavity. Screw wood screws through the holes in the side brackets of the smoke detector and into the wall or ceiling using a Phillips screwdriver. Restore the electricity to the room.