Wet carpet when something sits on the carpet for a long period?

In my office, if something sits on the carpet that has a good weight to it, when I lift it, the carpet is wet. No other part of the carpet is wet but if I sit a box with stuff in it or a desk without legs, the area is wet. I thought maybe it was just one area of the room but once I removed it, the wetness didn't come back. Is the room sweating,or is the air condition too cool ? I thought maybe water was getting in the house from outside, but it doesn't happen to any other room.