Quote Originally Posted by jp1 View Post
Our CO detector was actually doing 5 quick chirps. According to the manufacturer website that means ‘time to replace’ because it is 5-7 years old. We have another one downstairs on the wall outside the hallway where the furnace closet is. That’s our only gas appliance inside (hot water heater is also gas but it’s outside so not an issue) so I’m not too worried but I still will order a new CO detector for upstairs.
Another common way for smoke detectors to let you know their sensors have died of old age is by having a false alarm for several minutes, then being quiet for 20-30 minutes and having another false alarm. Very unnerving if you don't know that's what the false alarms mean and you're desperately sniffing around trying to find any hint of smoke or burnt smell.