We have had 2 Nest for some time. About a week and half ago, I replaced our 2 smoke/co alarms with 2 Nest Protect.

Around 5am yesterday, we were awaken with a CO leak warning. I hushed alarm and it alerted levels were rising. I turned off furnace and opened up house and check on everybody. About an hour later, the Nest Protect gave the all clear message. I closed windows and doors (it was below freezing out). I waited a bit and turned furnace on, and before too long got the CO alert again. I cleared house and turned off furnace. It was Sat. but got my heating and cooling guy out later in day.

I had some clogged igniters (2 out of 3) that was causing gas to get into system before finally firing.

I have no idea if old alarms would have alerted me as quickly as nest protect did, but I am glad to have these in my home now.

Thanks for great product.