Factory installed CO Detector life span

Good God there is some bad info on this thread. Detectors for anything come both in hardwired versions and battery powered versions. The price varies widely depending on the sophistication of the detector and the profit margin of the maker. They all work, some better than others with digital readouts giving you a constant level of CO in PPM. CO has virtually the same specific gravity as air and will not automatically rise to the ceiling. Place the freakin detector where you will be breathing air from! They all have an expiration date printed right on them. If you use a battery powered version change the batteries as required. Regardless of which kind of detector or what powers it make sure it is not expired and test it regularly.