My CO2 detector has been going off since like 10:00. DH and I are arguing about this. We are in a condo building. The hotwater heater is 2 floors above us so that can't be the problem. Although the heater and stove pilot are lit neither is running. DH says that this means they can't be the problem. There is nothing else we can think of. Nobody is sick or showing any symptoms of problems. It is nice out and all the windows in the house are open. The detector is reading high. DH feels it is the battery and I don't have another one here that fits and can't get it til the morning. He has gone to bed. I'm afraid to go to sleep and keep going around checking on everybody. But I definitely do not have any symptoms of problems. Also, when he put the detector outside it kept beeping. Any thoughts on this if you are awake this crazy late?