"ap" wrote in message
ups.com...
Hello,
After shopping around much, purchased a nighthawk digital for $33 from
wal-mart.
These are expensive and I'm wondering if the best placement would
be high in the hallway near the bedrooms. There are 3 bedrooms that are
occupied.

Is this a good idea?

As I recall, the specific gravity of CO is right at .97 with the air we
breathe at a 1.0. Based on that information, even though it's lighter than
air, it's not going up or down fast.