New pipe burn in me thinks. Do NOT ignore the CO regardless, you did the right thing. One of my CO's is directly behind the stove in the basement (CO placement and basement install are whole other threads), it is dependable and sensitive to the point that if I start my truck in the tuck under garage on my split level WITH the garage door open of course and the entry door closed, it does go off in less than 2 minutes. Only time the stove has caused it was for legitimate reason, i.e. leaky door seal on start up. Again, do NOT ignore a correctly functioning CO detector. Did someone mention pictures?