A single chirp means the battery is low or the detector should be replaced.
Single beeps: Single beeps that occur 30 seconds to one minute apart usually suggest the battery in your device needs to be replaced. However, they can also signal other issues with your device, including dust in the sensors or that the unit has reached EOL (end of life) and needs to be replaced.
As the battery in a smoke alarm becomes weak, the smoke alarm will "chirp" about once a minute to alert you that the battery needs to be replaced. Note: Only the alarm with a low battery will chirp.
It's time to change the battery
Low batteries are the most common reason smoke detectors beep or send a trouble signal to your security panel, when there is no smoke or fire. As the battery weakens, the device will beep regularly to let you know it's time to replace it.
Smoke alarms alert you with three beeps in a row. Carbon monoxide alarms alert you with four beeps. A single chirp means the battery is low or the detector should be replaced.
The most likely reason smoke detectors go off unexpectedly is that people aren't changing the batteries in them often enough. In most sensors you might think of, the strength of the signal goes up when they detect what they're supposed to. Common causes of smoke detector false positives around the house.
The battery may need to be replaced. An alarm will chirp every 30 to 60 seconds for a minimum of seven days. With a "low battery" announcement, disconnect the unit and replace the batteries.
Most hard-wired smoke detectors include a 9-volt backup battery that's supposed to kick in if your home loses electricity. If that battery is running low, your detector alerts you with a high-pitched beep.
CO alarm life span
The CO alarm will beep every 30 seconds or display ERR or END. If a CO alarm is at its end-of-life, replacing the battery will not stop the beep.
3 chirps (about 1x per minute): Malfunction chirp
Replace with a new alarm as soon as possible. Check to ensure that your alarm is not expired and in need of replacement.
In domestic properties, your CO alarm can be triggered by any fuel burning appliance such as gas cookers, boilers and ovens. All of these appliances give off small traces of CO, but the levels can rise slightly when adequate ventilation isn't provided, or the venting is blocked or clogged by dust.
Your alarm manufacturer may have included a blinking red light to let you know it's time to test the alarm again. The Batteries are Low: Usually accompanied by a loud beep, a blinking red light could mean the batteries in the unit are low. Consider adding fresh batteries and running a test to make sure it's working.
If your hardwired machines continue to beep in the absence of a battery, it's most likely because the backup battery has become active. Keep in mind that a backup battery unit is only available with a hardwired device, so if your smoke alarm is battery-only, the chirping is coming from somewhere else.
As the battery in a smoke alarm gets weak, the smoke alarm will “chirp” about once a minute to let you know that the battery needs to be replaced. Note: Only the device with a low battery will chirp. The other interconnected alarms should be silent.
Replace Expired Smoke Alarms
Smoke detectors have a life span of five to ten years. If this is the problem, the beeps will likely present in a specific chirping pattern. Inspect the unit carefully and find the expiration date. If the smoke alarm is beyond that date, it's probably time to buy a new one.
Dust, Dirt and Environmental Smoke
Dust and dirt that comes from activities like remodeling may set off your smoke alarms. To clean your smoke alarm, open it up carefully, and look inside for dust or dirt. Use a vacuum attachment or electronic aerosol cleaner to remove dust particles.
The CO alarm sounds if your sensor detects a buildup of carbon monoxide in your home—usually before you start sensing symptoms. With a low CO level (50 ppm), it may take up to eight hours for the alarm to go off. Higher carbon monoxide levels (over 150 ppm) can trigger an alarm within minutes.
A carbon monoxide detector does not sound the same as a smoke detector. It sounds similar to the way a smoke detector beeps when it needs a battery replacement. It will beep at a regular rate to alert you of a carbon monoxide presence.
If the detector's a plug-in device in an outlet, it's likely a carbon monoxide detector, and the device should be marked as such. Usually, a carbon monoxide detector will also be labeled on the front near the test button.
The green light on my smoke alarm has gone out, what does this mean? The AC power has been interrupted. Check the circuit breaker and AC wiring to correct the problem.
For most residential smoke detectors, blinks are common; you need to be conversant with the colors showing. Different smoke alarms use the green and red LED to indicate the device's power status such that a flashing green means low battery while a constant blink means AC power is connected.