How does a Carbon Monoxide Detector work?
From About.com (http://chemistry.about.com/od/howthingswork/a/codetectors.htm)
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 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):
Do CO alarms operate differently than smoke alarms?
Although they may look and sound similar, CO alarms and smoke alarms are designed and intended to detect two separate, distinct hazards. Therefore, to help protect your family from both hazards, it's important to install both UL Listed CO alarms and smoke detectors.
How do I install my CO alarm?
Follow the installation instructions found in the manufacturer's use and care booklet that accompanies the product. Proper installation is an important factor in receiving optimum performance. It's important to follow these instructions exactly.
How do I take care of my CO alarm?
Like smoke detectors, CO alarms need to be tested regularly and cleaned as indicated in the manufacturer's use and care booklet. If the unit operates off a battery, test the detector weekly and replace the battery at least once a year.
Should I follow any safety tips for using and maintaining my CO alarms?
As with any product, read the manufacturer's use and care booklet for installation and maintenance guidelines. Keep these instructions on file for future reference.
If your unit operates off the battery, never allow anyone to "borrow" the battery. Like any appliance or power tool, a CO alarm can't work unless it has a functioning power source.
For more information, see - www.epa.gov/iaq/co.html