Abstract: A method, comprising: —providing a process space atmosphere at a process space atmosphere pressure; —providing an exterior atmosphere at an exterior atmosphere pressure that is different from the process space atmosphere pressure; —providing a passage via which the exterior atmosphere is in open communication with the process space atmosphere, and via which substrates are exchangeable between the exterior atmosphere and the process space atmosphere; —injecting an exchange fluid into the passage at at least one exchange fluid injection point, so as to effect a flow of exchange fluid that extends through at least a part of the passage, wherein said flow is directed towards—the exterior in case the exterior atmosphere pressure is greater than the process space atmosphere pressure; or—the process space in case the exterior atmosphere pressure is smaller than the process space atmosphere pressure.