A method for enabling transfer of an object from an interior of an airlock to a pressure vessel attached to the airlock and ensuring that an exterior door of the airlock cannot be opened when the interior of the airlock is pressurized includes actuating a first selector from a first position to a second position whereby the first selector causes the exterior door to be locked and sealed. Thereafter, actuating a second selector from a first position to a second position thereby closing a vent from the interior of the airlock to the atmosphere. Thereafter, actuating a third selector from a first position to a second position thereby opening a vent between the interior of the airlock and the pressure vessel thereby enabling a door between the interior of the pressure vessel and the interior of the airlock to be opened.
