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How To Replace a Smoke Detector

Smoke detectors play an important role in home safety and security. There are several types of smoke detectors related to how they sense the presence of smoke. Ionization smoke detectors sense the presence of smoke by measuring the drop of ions in the air. This type of detector is set off by such things as cigarette smoke, heat from furnaces, kitchen ranges, and even electronic equipment. In photoelectric detectors, the smoke obscures and breaks a light beam in the detector itself. Smoke detectors are also divided into two categories based on whether they run on batteries or are hard-wired.

Replacing a smoke detector

Testing and replacing a smoke detector is easy . . . and wise.

Testing and replacing a smoke detector is easy . . . and wise.

  1. If your detector is a hard-wired unit, find the circuit breaker in your electrical panel that controls the smoke detector. It should be a dedicated circuit.
  2. Turn the circuit breaker off and label it so no one turns it on accidentally.
  3. Use a stepladder to gain access to the smoke detector.
  4. Remove the cover of the detector. Usually, you have to depress tabs on the sides of the detector to remove the cover. You also may have to rotate the cover slightly to remove it.
  5. Loosen the two screws that hold the detector to the base.
  6. Twist the detector base slightly and pull it free from the mount plate.
  7. Using a tester, check for voltage at the wires to the base of the detector.
  8. If there is no voltage present, remove the wire nuts one at a time. Untwist the wires and remove the detector.
  9. If your detector is a battery-operated unit, simply remove the cover following the above directions.
  10. Loosen the mount screws that hold the detector to the ceiling mount plate.
  11. Remove the detector.
  12. Remove the screws that hold the mount plate to the electrical box in the ceiling.
  13. Installation of the new detector is the reverse of removal.


Whether your smoke detector is hard-wired or a battery powered type, you should test it annually.

Simply press the press-to-test button and listen for the alarm. If it does not go off, plan on replacing the smoke detector as soon as possible.

If your smoke detector is a battery operated type, replace the batteries every six months at the latest.

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