In many documented tragic residential CO incidents the source of the CO has been a malfunctioning furnace / flue system - not a typical fire condition. The CO detector is the only detector able to detect this deadly gas condition in these instances. CO gas is odorless, colorless and deadly. CO gas is typically discharges hot causing it rise to ceilings, even though it is of almost identical density to air, the reason why ceiling detectors are my first choice. I advocate using