The Kitten Farm West has an attached garage, entered by the laundry room off the kitchen. Fortunately, this room can also act as an air lock, since it has both kitchen and garage interior doors. We use this when retrieving items from the garage, for example.
Unfortunately, because of its tile floor, laundry room is also where the downstairs litter box lives, which means the boys know exactly where the room is. Nor can we use the airlock feature if actually leaving, since the inner door would cut off access to the litter box.
Of course, we NEVER leave both laundry room doors and the exterior garage door open at the same time.
The boys never met a closed door that they thought should stay closed.
Good news: We made it 10+ days before Whitey decided to visit the garage.
Bad news: Once he decided to visit it, he made it first try. We chased him down, but now that he's seen Paris ...