I posted this in another tread but I thought that it was important enough to be mentioned in its own thread. CO alarm detection is not on by default. If you did not manually enable CO detection when you installed the device, it will not pick up CO alarms. I did not know this and did a little research. CO alarm detection is turned off by default because it apparently will shorten battery life somewhat. How much, I do not know or care. I want CO alarm detection. I think that this is very important. Here are the instructions to enable it and how to check and verify that it is enabled.
CO alarm audio detection set up. • • • • • Press and hold both the programming button and the tamper switch for 10 seconds. Remove and replace the battery. On battery replacement, watch the LED light. Look for a RED, RED, GREEN blink. If you see this, the device will listen for CO Test devices to be certain. NOTE detector alarm condition. When detecting both CO and smoke alarms, you may shorten battery life. Battery levels are supervised by most hubs.