So I finally got my hearth built, Selkirk chimney, and Jotul F500 (Oslo) installed. Looks great, and the first three break in burns went smoothly. As expected, there was a burnt paint smell and a very faint haze that I wasn't expecting, but I chalked it up to the paint curing. Absolutely no discernible smell of smoke. While I was away the next day, my sister lit the fourth fire and according to her the CO detector in the next room went off right around the 400 degree mark. I only have one, and thinking it might be a fluke, she borrowed the neighbors plug-in and that also went off. For the life of me I cannot find any leaks - everything seems to be sealed tightly and the stove appears to be drafting well. Even if I open the door mid-fire, there's no back-puffing that I can see. I let the stove cool down and ran another fire up to 500 degrees - no CO alarm going off, no smoke detectors going off. I want to leave this running overnight, but my wife is now concerned. Any suggestions as to what could be going on, and what I can do to give us peace of mind? Thanks so much!