The side doors have no airlock, so to EVA into space the entire module must be depressurised (Space Brain, The Exiles, Bringers of Wonder part 2). Fortunately boxes, lasers and other loose items do not float out the door when the astronaut leaves the module.
Initially there were two grilles on either side of the door, with a small control panel beneath each. In Collision Course an additional larger control panel appears on one side, which is sometimes used to operate the doors. The control panel remains in Year 2, but the grilles on either side are gone.
In Matter of Life And Death, the exterior doors gain slots either side for the hand rails (and the first use of steps). The exterior side doors in Earthbound have a "airlock control", which is still present at the end of the year 1. By year 2, the exterior is bare.
Behind the scenes from Matter of Life And Death showing the exterior of the passenger module.
Copyright Martin Willey. Thanks to Marcus Lindroos.