A carbon monoxide (CO) alarm sounds as a continuous series of four loud beeps in a row—beep, beep, beep, beep—repeated until the alarm is addressed. This distinct pattern indicates that carbon monoxide is present in your home and you should immediately go outside, call 9-1-1, and stay out for safety
. Additional sounds from a CO alarm include:
- A single chirp every 30 or 60 seconds, signaling a low battery that needs replacement
- Some models emit a series of five beeps or other chirps indicating the alarm has reached the end of its life and must be replaced
- Other alerts such as two beeps for faulty sensors or three beeps for end-of-life warnings vary by manufacturer
In summary, the emergency alert for carbon monoxide is four loud beeps repeated continuously, which is different from smoke alarms that typically sound three beeps in a row. This helps distinguish the type of hazard quickly
