"Toller" writes:

You are correct about not being near the floor. Although it is about the
same density as air, it is likely to be warm so it will tend to go up. I
will move my detectors up immediately! Thanks.

But I still think the basement is the right place. A problem with the water
heater is much more likely than a cracked heat exchanger. I have two, maybe
I will split them up. (of course, if the OP doesn't have a gas water heater
you would be right about that also. Live and learn...)

Nd not to mention gas clothes dryers.

But, how old is your furnace? And do you feel lucky? It's worth
noting the furnace runs a lot more often than a water heater and does
a whole lot more combustin'.... and your water heater doesn't have a
bloewr and duct work attached to help distribute it throughout the
living area.

So if you have two CO detectors one on the sleeping level is
definitely a good idea.

--
Todd H.
http://www.toddh.net/