Since I wrote my original post on this topic fading batteries in CO2 detectors have reached epidemic proportions. There are now two going off in my own building, (which I can’t hear inside my own apartment thankfully, just the hall), there is a second one going at my boyfriend’s place, (as well as the original still beeping), and I heard them in two different buildings when visiting friends in the past few days. Then… my own started going off. My first thought was… “This is happening to the whole city! What’s going on?!” and it dawned one… this IS happening to the whole city. In 2004 a new law was enacted requiring C02 detectors along with smoke detectors in every apartment. The final date for compliance was June 2005. So if most building owners are like mine… a goodly portion of the city got CO2 detectors installed on or around June 30th, 2005. I’m betting the battery life in a CO2 detector is about… 2 years. So… for your own safety, and the sanity of your neighbors, check the battery in your detector and get them changed. Please?