Carbon monoxide (CO) and combination alarms should be mounted in or near bedrooms and living areas, no closer than 20cm from the ceiling. If mounting on a ceiling please make sure it is at least 20cm away from the wall. Because carbon monoxide is almost the same density as air, it will disperse evenly throughout the air in a room.
We recommend you install a carbon monoxide or combination alarm on each level of a multi-level home. If your home has only one CO or combination alarm, it should be installed in the main bedroom or in the hallway outside of the sleeping areas. Place the alarm at least 1.5m away from fuel-burning appliances. Make sure nothing is covering or obstructing the unit. Do not place the unit in dead air spaces or next to a window or door. CAUTION: Carbon Monoxide alarms will only indicate the presence of carbon monoxide at the sensor. Carbon monoxide may be present in other areas of your home.