SD, I went to the Xintex website (How do you know all this stuff?) and looked at the Fireboy products which do seem like the appropriate sensor for the task. From their website I copied this:
Ideal for boats requiring additional CO alarm protection and for boats without a CO alarm.
The CMD-1MR-9V uses an advanced biomimetic sensor to determine CO levels. Time Weighted Average sensor technology is used to eliminate false alarms.
Install one unit in every sleeping area, galley, and confined space for adequate protection. Extremely low battery consumption – only .016 mA.
Ceiling or wall mount
Dimensions: 4.75” diameter x 1.5” depth
9V battery included
1-year limited warranty
UL 2034 Listed for Marine use.
9V battery powered
Carbon Monoxide Detector
By their description I would need 4 units, galley, V-berth, head and engine compartment area to fully cover my 31' vessel. That would be about $600 worth of sensors. When compare to a life, that is a bargain but is still a substantial investment when compared to other safety equipment that is needed. Your suggestion is appreciated but my priorities move this quite a ways down on the list.