Carbon Monoxide (CO²)  Detectors As part of our jobs, we go into a lot of houses each and every week.  In  all too many of these homes, we notice that the CO² detectors are mounted incorrectly. CO² is a gas. Unlike smoke, which rises, CO² is a heavy gas, and it settles to the lower level. Since smoke rises, your smoke detector should be mounted high, so that it senses smoke at the earliest opportunity. Since CO² stays at the lowest level, your CO² detector should be mounted low- below the level of your head while sleeping. All too often, while we are in houses, we see that the CO² detector is mounted over head level, we've even seen them mounted to the ceiling. If the detector is mounted over head level, by the time it senses a CO² buildup and the alarm sounds,                                              YOU ARE DEAD! Please - make sure that your CO² detector is mounted low.