Why Do Hard Wired Smoke Detectors Chirp?

History

• Modern smoke detectors became widely available in the United States in the early 1970s. The proliferation of smoke detectors in households led to a steady decline in prices, resulting in even more households being able to afford multiple detectors. Smoke detectors are readily available at home improvement and department stores and are very inexpensive.

Technology

• Smoke detectors come with two basic sensor technologies: ionization and photoelectric. Both types of sensors scan the air for small particles that indicate the presence of smoke. The photoelectric sensor is more sensitive to slow, smoky fires while the ionization sensor is more sensitive to open-flame fires. Since it's impossible to predict what type of fire may occur, the United States Fire Administration recommends installing both types of detectors, or dual-sensor detectors, in the home.

Power

• For many years, the standard power source for smoke detectors has been the 9-volt battery. Battery-powered smoke detectors require annual battery replacement and, if an alarm is triggered, only sound the individual alarm that detected smoke. As the technology has improved, more homes are using hardwired smoke detectors. Hardwired detectors still use a battery for backup power, but that battery requires less frequent replacement and, in the event the battery fails, the detector will still function if household voltage is present. Hardwired alarms can also be wired together, causing an alarm condition at one detector to trigger all the alarms in the home.

Chirping

• If a smoke detector is chirping, the cause is most likely a weak or improperly installed battery. Chirping is a short tone emitted by the smoke detector at regular intervals. The interval may range from 20 seconds to a minute and get weaker over time if the detector is battery powered. The chirping sound can be eliminated by replacing or reinstalling the battery, or by replacing the smoke detector. If the sound the smoke detector emits is high-pitched, or occurs intermittently, then it's likely that some environmental condition or failure within the detector is triggering an alarm condition.