Vehicle sidewall air distribution duct with inflatable gasket

For a vehicle having laterally opposed, generally vertical sidewalls and an underlying integral floor, an air distribution duct being of modified rectangular cross-section and extending longitudinally along the floor of the vehicle and along one sidewall thereof, said air distribution duct having vertically opposed top and bottom walls and horizontally opposed sidewalls including a laterally outer sidewall proximate to said vehicle sidewall and a spaced, laterally opposed sidewall facing interiorly of the vehicle, said duct including a narrow top extending vertically upward along said exteriorly facing sidewall, said interiorly facing sidewall of said duct being laterally offset adjacent said floor including a short height vertical portion and a right angle horizontal portion defining a recess within the interiorly facing sidewall, a longitudinally extending series of floorward-facing blow perforations within said horizontal portion for permitting air distributed through said duct to enter the interior of the vehicle adjacent to said floor, at least one longitudinally extending inflatable gasket within the interior of the duct adjacent the interiorly facing sidewall and parallel to said series of perforations and including a normally retractable portion in the non-inflated state retracted to one side of the perforations, but projectable across the perforations to seal off the flow of air through said floorward-facing blow perforations to limit distribution of air within said duct to said narrow top portion along the vehicle sidewall.