I bought a CO detector last night....yea, yea... I know I should have had one long ago. I actually read the manual that came with it... one paragraph caught my attention....CONDITIONS WHICH CAN RESULT IN TEMPORARY CO SITUATIONS... 1) Wind direction including high gusts of wind. Heavy air in the vent pipes (cold,humid air with extended periods between cycles)... (this would be with NG or oil furnaces not pellets) 1) Negative pressure differential resulting from the use of exhaust fans 3) Simultaneous operation of several fuel burning appliances competing for limited internal air. 4) Vent pipe connections vibrating loose from clothes dryers, furnaces or water heaters. 5) Obstructions in or unconventional vent pipe designs which can amplify above situations. 6) Extended operation of unvented fuel burning devices (range, oven, fireplace, etc) 7) Temperature inversions which can trap exhaust gasses near the ground. As you can see, if you are using more than a pellet stove in a "tight" home you may have a problem with higher CO levels... not guaranteed but possible. Just something to think about.