Smoke Detectors / Alarms

Carbon Monoxide FlowchartImportant Notice

Check your detector's expiration date. Smoke and Carbon Monoxide detectors expire 7 to 10 years from their date of manufacture. They will chirp when they expire.


Quality, not price, should be the determining factor when you decide to buy smoke detectors. Check for the following:

  • Laboratory label, ensuring that samples of the model you are buying have been carefully tested.
  • Alarm loud enough to awaken the family through closed bedroom doors.
  • Malfunction signal, to warn you when batteries are worn out or weak.
  • Manufacturers' warranty of at least five years.
  • Ease in maintenance and cleaning, which should be simple, as by regular vacuuming and dusting.

Which Type?

Ionization smoke detectors contain a small amount of radioactivity that conducts electricity. Electric current flows continuously between two electrodes in the chamber. When smoke particles enter, they disturb this flow, causing the alarm to go off.

Photoelectric smoke detectors contain a beam of light and a photocell within the chamber. When smoke enters, it deflects the beam, causing it to strike the photocell and set off the alarm.

Which Is Better?

Ionization detectors are more sensitive to the tiny particles of combustion that can't be seen or smelled - those emitted by flaming fires. Photoelectric detectors are more sensitive to the large particles of combustion emitted by smoldering fires. Consequently, ionization detectors will respond faster to flaming fires, and photoelectric detectors faster to smoldering fires.

The differences between the two types are generally not critical since the difference in response time is only a matter of a few seconds. Since most home fires produce a rich mixture of smoke types, with detectable amounts of both large particle and small particle smoke early in the fire's growth, either ionization or a photoelectric detector will meet most needs.


Buy as many smoke detectors as it takes to give your home complete coverage. You increase your chances of survival with each one that you have; one on each level of the house is the absolute minimum.

You should have a smoke detector in a bedroom if the occupant smokes or sleeps with the door closed.

When bedroom doors are left open, you should have at least one in the hallway outside the bedroom area.

Maintenance Checklist

  • Test your smoke detector at least once a month, either by releasing smoke into the chamber or by pressing the test button.
  • Replace weak or worn out batteries at once.
  • Never borrow smoke detector batteries for other uses.
  • Keep extra batteries on hand.
  • Change batteries at least once a year.
  • Dust and vacuum smoke detectors at least twice a year.
  • Make sure smoke detectors are working when you return home after an extended absence.