It is one of the locations I place the monitor.
Again there are no state protocols here, so the EPA guidelines are followed.
And there is no state list of approved devices.
This is from the EPA guidelines. Bold is mine.
• The detector should be at least 50 centimeters (20 inches) from the floor, and at least 10
centimeters (four inches) from other objects. For those detectors that may be suspended, an
optimal height is in the general breathing zone, such as two to 2.5 meters (about six to eight
feet) from the floor.