Smoke alarms send out a piercing, pulsating alarm of 85 decibels -- three ear-shattering alarms, called the "horn pattern," followed by a pause, and then repeated. This indicates they've detected smoke or other products of combustion. And they quietly chirp once a minute when their batteries are dying. In either event, you need to know how to reset your alarm so all's quiet and the device returns to its duties as a standby safety sentry.
If you don't know the cause of the alarm, which could be broiling food in the oven or a dusty furnace kicking on, leave the alarm on while you investigate whether you have a fire. If so, get out and call the fire department. In the case of dense smoke, the alarm will stay on despite your attempts to reset it.
Resetting the Alarm
If you know that broiling or another nonfire cause has triggered the alarm, look for a prominent button labeled "Hush" or "Silence" on the smoke alarm. It may be a single or two-part, thumbprint-sized button with a slight indentation on newer models, or two small, transparent buttons each the size of a pencil eraser on older versions.
Find the "Hush" button on the initiating alarm if you have hard-wired alarms, such as the First Alert 9120B, in a series. Look for an alarm -- it should be the closest one to the triggering source -- with a flashing red LED and press its button. These alarms, which can be either low-voltage or 120 V AC, have been required by code on new homes since 1980 and include a battery backup to offer dual protection.
An unusual design that plugs into a light socket, the DuPont PS-131 self-charging smoke alarm can be reset by flipping the light switch.
Avoid removing the alarm from its ceiling mount and popping out the battery or pulling out its AC power supply; this removes your protection.
Replacing the Battery
Remove the alarm from the mount and flip open the battery drawer or compartment to replace the battery, typically a 9-V. Once it starts to chirp, the twittering sound may last for seven days, but it's best to address it as soon as you notice the first chirps.
If you have a chirping hard-wired battery, the cause may be an incorrectly grounded orange interconnect wire. Disconnect the battery from the mount and rewire as necessary to make sure the orange wire of the unit goes to a wire nut to be joined with the orange interconnect wire that runs in the wall or ceiling.
Note: Smoke alarms with lithium ion 10-year batteries cannot be replaced. You need to discard and replace the entire unit. To eliminate continued chirping once they are in the trash awaiting pickup, check the manufacturer's instructions; you may have to break out a cross-hatched area near the product label. Mark the back of the new unit with a note such as, "Replace in June 2025."
Test your smoke alarm weekly by pressing the "Test" button, located near the "Hush/Silence" button. If the alarm doesn't sound or makes only an erratic noise, retest it by holding it down for 10 to 20 seconds. Next, clean the sensing chamber and the openings in the housing with an air duster can for electronics or a vacuum hose. Replace the unit if another touch of the "Test" button doesn't work.
Alarm Keeps Chirping
If your smoke alarm keeps talking to you after you put in a new battery, check the following:
- Remove the replacement battery and check it on a multimeter to confirm that it is fresh and has a 9-V charge.
- Double-check that the battery freshness pulltab found in new units has been pulled out and that the battery drawer is firmly shut.
- After a power outage, hard-wired smoke alarms should reset automatically, and you can hit the "Test" button to confirm. If you hear chirping, the power outage may have revealed failing batteries that need replacement.