publication_number US 7980266 B2 abstract a one way soffit vent has an upstream valve seat and a downstream vented cover having a boss extending in the upstream direction a valve disk is reciprocally mounted on the boss and biased against the valve seat application_number US 67118907 A description turning to fig1 a building 10 has an enclosed room 12 with an exhaust fan 14 in the ceiling the outlet of the exhaust fan is connected to one end of a duct 16 the other end of the duct is connected by hose clamp 18 to the upstream end of soffit vent 20 as seen in fig1 the soffit vent is mounted through the soffit 22 of the building soffit vent 20 is detailed in fig2 to 4 turning to these figures the vent may have in downstream order a first sleeve section 30 a second sleeve section 32 which is connected to a valve seat 40 and a cover 42 a valve disk 44 and a coil spring 46 may extend within the second sleeve section 32 upstream of the cover 42 the first sleeve section 30 may have an upstream smaller diameter cylindrical stub 52 terminating at a step runner 53 to a larger diameter concentric downstream cylindrical stub 54 each cylindrical stub 52 54 may have a pair of outwardly projecting tabs 56 the first sleeve section.