Abstract: A transfer port apparatus is provided for transferring an item through a port formed in a wall of a housing and into an interior region of the housing. The apparatus includes a door collar assembly formed to include an aperture therethrough, an arcuate groove surrounding the aperture, and threads for coupling the door collar assembly to the wall of the housing so that the aperture is in communication with the port to permit insertion of the item into the interior region of the isolation chamber. The apparatus also includes a door gasket located in the arcuate groove of the door assembly, and a door configured to be inserted into the aperture of the door collar assembly. The door has an outer peripheral surface aligned with the door gasket. The apparatus further includes a mechanism for biasing the door gasket against the outer peripheral surface of the door to retain the door in the door collar assembly and to seal the door in the door collar assembly.