I have virtually no airflow to my kitchen or garage vents. When I looked at the ducts coming from the furnace I have (2) 3" ducts coming out (maybe 4" but I think 3"). One goes to the bedroom and front bath, one runs to the rest of the rv. The bath/bedroom line is about 4' long. The other runs 20' +/- to the kitchen, garage and 1/2 bath. There are (4) vents (3 openings) on the run to the kitchen/garage with approx 26" sq. in. of vent area (vents from the main run, not the actual exterior vent itself). I think the runs are 3", maybe they are 4". Either way that's 12" max sq. in. air carrying capacity (assuming 4") on a 20' run with (3) openings and (4) vents. I don't know what the little squirrel cage fan produces in CFM or SP but no way it can push air that far with that many much vent area given that the other run has so much less resistance. I may be wrong, but the math says I am likely right.