The primary distinction between a smoke detector and a carbon monoxide detector lies in their functions: smoke detectors serve as fire protection devices, whereas carbon monoxide detectors specifically identify the presence of carbon monoxide, which can originate from various sources beyond just fires. Moreover, smoke detectors are usually mounted on ceilings or high on walls since both heat and smoke ascend. In contrast, carbon monoxide detectors are generally placed closer to the ground because carbon monoxide is a dense gas that tends to settle lower.