Main Man wrote:
Dont know which country you're in but you want 1 with long term
stability of CO cell; many don't.
The HSE (UK Govn't body} only found 2 satisfactory.
1 was "SF" brand, 1 "Kidde"; latter available both sides of pond.
http://www.kiddesafetyeurope.co.uk/C...e+Alarms.shtml

Hi. Thanks for your reply. I'm in the United States. The brand I bought
is a Kidde, but apparently Kidde makes many different models. The one I
bought is a combined carbon monoxide and smoke detector. Now I hear
that it is not advisable to have the two combined in one device.
Supposedly, the carbon monoxide detectors should be intalled at a much
lower level than the smoke detectors. The smoke detectors should be
installed on a ceiling, whereas the CO detectors should be at about the
level of an electrical outlet or not more than five feet above the
floor. I was told that CO may not rise as high as the ceiling fast
enough to be detected. By the time the CO reaches the ceiling-mounted
detector, a person will have breathed in a substantial amount while
lying in a bed that is much closer to the floor. The one I bought is
only battery operated. I hear that they make CO detectors that can be
plugged into an electrical outlet but they have battery backups in the
event that there is a power failure.