One for every room I intent for humans to survive in, plus one in each car. Also recently upgraded to hardwired CO/smoke detectors and each bedroom also has a combination alarm that uses Z-Wave to alert me anywhere, just as a backup. Also, we practice fire and earthquake drills monthly, along with a couple of other scenarios that are more rare/less dangerous.
One for every room I intent for humans to survive in, plus one in each car. Also recently upgraded to hardwired CO/smoke detectors and each bedroom also has a combination alarm that uses Z-Wave to alert me anywhere, just as a backup. Also, we practice fire and earthquake drills monthly, along with a couple of other scenarios that are more rare/less dangerous.