I was inspecting my return air vents in my house yesterday. My house is a two story 4 bedroom. My daughters room is by far the most uncomfortable of the bedrooms, so out of curiosity, i placed a piece of toilet paper on the return air vent. Well the paper stuck. But my sons room that is across the hall from hers couldn't hold the paper. I checked all the bedrooms and his is the only one that doesn't hold the paper. How would I go about finding where the problem is with this return air vent?