Quick Answer
Press and hold the reset/test button for 5 to 15 seconds(check your model's manual for the exact duration) until the unit chirps or the indicator light changes. Only do this after confirming there is no active CO emergency. If a continuous 4-beep pattern is sounding, evacuate and call 911 first; do not attempt to reset the unit while it may be detecting real carbon monoxide.
Step 1: Confirm It Is Safe to Reset
Before pressing any button, identify what the alarm is actually telling you. CO detectors use distinct beep patterns for different conditions, and confusing them can be dangerous.
Continuous 4-beep pattern, repeating
This is the CO emergency alarm on most US detectors. Evacuate everyone immediately, including pets, and call 911 from outside. Do not attempt to reset the unit. Do not reenter until the fire department clears the space.
Single chirp every 30 to 60 seconds
This is a low battery warning, not an emergency. Replace the battery, then perform the reset steps below.
Five chirps per minute
This typically signals end of life. The electrochemical sensor has expired (5 to 7 year lifespan). Resetting will not fix this; the unit needs to be replaced entirely.
Chirping right after you replaced the battery
This is usually residual charge or a memory state that needs to be cleared. Proceed with the reset steps below.
Step 2: The Reset Procedure
Once you have confirmed there is no active emergency, most consumer CO detectors follow a similar reset process, though the exact button-hold duration varies by brand and model.
Locate the reset/test button
On most units, this is a single labeled button on the front face of the detector. Many models combine the test, silence, and reset functions into this one button.
Press and hold
Hold the button down for the duration specified in your manual, typically 5 to 15 seconds. Do not just tap it; a full reset requires a sustained press.
Wait for confirmation
The unit should chirp once or twice, or the indicator light should change color or pattern, confirming the reset completed and the sensor memory has cleared.
Watch for continued chirping
If the unit chirps again within a minute or two after the reset, the underlying issue (weak battery, sensor fault, or end of life) has not been resolved and the reset alone will not fix it.
Skip the reset button altogether
A monitored CO detector alerts a professional, not just you.
NetSecure360 installs ADT-monitored CO detectors that report faults and low-battery conditions to our monitoring center directly, so a chirping detector never goes unnoticed.
When the Reset Button Does Not Work
A CO detector that will not reset, or that resets and then chirps again shortly after, is telling you something the reset button cannot fix. Common causes:
Battery not seated correctly
Remove the battery, check the polarity markings, and reinsert firmly. Make sure the pull tab from original packaging has been removed, as it sometimes remains lodged in the compartment on new units.
If the battery is seated correctly and the reset still fails, check the manufacture date printed on the back of the unit. Electrochemical CO sensors have a rated life of 5 to 7 years per UL 2034. A unit at or past that age cannot be reset back into working order because the sensing cell itself has chemically degraded; it must be replaced entirely, not repaired or reset.
For hardwired, interconnected detector systems, a unit that will not clear its fault may be losing signal from another detector in the chain. Check that all interconnected units in the home are powered and functioning; a fault on one unit can sometimes display on all interconnected units simultaneously.
Frequently Asked Questions
How do I reset my carbon monoxide alarm?
First confirm there is no actual CO emergency: if the alarm sounded a continuous 4-beep pattern, evacuate and call 911 before touching anything. If it was a false alarm or you just replaced the battery, press and hold the reset or test/silence button (usually the same button) for 5 to 15 seconds, depending on the model, until the unit chirps or the light changes to confirm the reset.
Why won't my carbon monoxide detector reset?
If holding the reset button does not stop the chirping or clear the fault indicator, the most common causes are a battery that is not seated correctly, a unit past its 5 to 7 year electrochemical sensor lifespan, or a hardwired unit that has lost its interconnect signal from another detector in the chain. Check the manufacture date on the back label; if the unit is at or past its rated life, it needs to be replaced, not reset.
Is the reset button the same as the test button?
On most consumer CO detectors, yes, one button serves both functions. A short press typically silences a false alarm or clears a fault code, while a longer press (5 to 15 seconds) performs a full sensor reset. Some models use the terms 'test/silence' and 'reset' interchangeably in their manuals.
Do I need to reset my CO detector after replacing the battery?
Yes, on many models. Inserting a new battery does not automatically clear a residual fault or chirp state on some units. After a battery change, press and hold the reset button for the duration specified in your model's manual, typically 10 to 15 seconds, to fully clear the unit's memory and confirm it is operating normally.
What does it mean if my CO alarm keeps needing to be reset?
A CO detector that requires frequent resets, especially without an obvious cause like a battery change, may be detecting low-level CO intermittently, have a failing sensor, or be near its end of life. Do not simply keep resetting it and ignoring the pattern. Check for a nearby CO source (a fuel-burning appliance, an attached garage) and consider having a professional inspect your home's combustion appliances.
Sources
- 1. UL 2034: Standard for Single and Multiple Station Carbon Monoxide Alarms (sensor lifespan, reset behavior)
- 2. NFPA 720: Standard for the Installation of Carbon Monoxide Detection and Warning Equipment
- 3. CDC Carbon Monoxide Fact Sheet: emergency response guidance
Never Manage a CO Alarm Alone Again
NetSecure360 is an authorized ADT dealer. Our monitored CO detectors report faults, low batteries, and true CO events directly to our 24/7 monitoring center, so you are never the only line of defense.