You must have a CO detector installed in your home if you have gas appliances and/or an attached garage. If you only have one carbon monoxide alarm, install it in the hallway near the sleeping area. Make sure you can hear it from every bedroom, so it can wake everyone up if the alarm goes off while you are asleep. Additional alarms on each level of your home provide extra protection. Carbon monoxide weighs about the same as air and distributes evenly throughout a room. A CO alarm will be effective if it’s on the ceiling, near the baseboard or anywhere in between. Do not install a CO alarm right next to a combustion appliance, like a gas or oil furnace. Instead, install the CO alarm at least 15 - 20 feet away from these appliances whenever possible.