The smoke alarm pattern is three long beeps with voice "Fire!," a 1.5-second pause, and three long beeps repeating. The red LED blinks in time with the alarm pattern.
The carbon monoxide (CO) alarm pattern is four quick beeps with voice "Warning! Carbon Monoxide." repeating every 5 seconds. The red LED blinks in time with the alarm pattern.
The smoke alarm takes precedence when both smoke and carbon monoxide are present.
Below are two convenient charts from the User Guide that reference various sections within the guide. Consult the User Guide for more info.