Any time a digital unit displays a number with or without an alert, assume it senses carbon monoxide. Leave the home and call 911.
This is usually caused by the absence of AC power to the smoke alarm.
Follow our simple steps for carbon monoxide detector battery replacement and learn more about how to properly maintain your CO alarm.
Combination alarms save space in your home, and they mean you only need to test and change batteries in one device rather than two.