I thought I would look this up and this info is according to UL. I also looked up LP for sake of argument to be sure we all have the correct info. LP is 1.55 times heavier than air. According to what I have read and looked up this is the statement related to LP detection.
Since propane is heavier than air, propane detectors should be placed no higher than the pillows on your bed, and generally lower than that if possible.
Where Should I Place a Carbon Monoxide Detector?
Because carbon monoxide is slightly lighter than air and also because it may be found with warm, rising air, detectors should be placed on a wall about 5 feet above the floor. The detector may be placed on the ceiling. Do not place the detector right next to or over a fireplace or flame-producing appliance. Keep the detector out of the way of pets and children. Each floor needs a separate detector. If you are getting a single carbon monoxide detector, place it near the sleeping area and make certain the alarm is loud enough to wake you up.
From the Underwriter's Laboratory (
http://www.ul.com/consumers/co.html):
I just thought I would share this to reinforce what has been stated in the post.
OP I think you gave a defective detector and would recommend replacing it.
Linear Mode
