Testing the Waters

My own experience, and that of most photographers I know, is that we are a nomadic lot much of the time. Almost all of us have stories of jury-rigged darkrooms. This situation usually means apartment living. Landlords don't tend to appreciate the modifications necessary to provide ventilation and light-proofing in that spare bedroom. Since knocking holes in walls is probably out, you could try this through-the-door approach.

Tools:

Hammer
Drill and bits
Nailset
Screwdriver
Saw-power or hand
Framing square
Saber saw or keyhole saw

Materials:

inexpensive solid-core replacement door to fit door opening
latch set and hinges to suit door (or re-use from original door)
bathroom-type box fan
furnace filter
poplar or maple 1 X 2s
2 - 4' X 8' sheets 1/4" luan or birch plywood
2-1/2" drywall screws
4d finishing nails
carpenter's glue
Caulk

Construction

The diagram should be self-explanatory. Dimensions are not given, since they will vary with different doors. The vent consists of two identical 1X2 frames attached to opposite sides of the door with screws driven through pilot holes and glue. Be sure to allow enough space around the frame for the door to open, and for the doorknob to be accessible. Caulk the area where the door and frame meet.

Opening are cut through the door more or less as shown. The area inside the frame is painted flat black, and caulked. Two identical sheets of plywood are cut to fit the frames, with two openings cut through each sheet as well. The inside surfaces of the plywood are also painted black. The plywood is attached with glue and finishing nails. Build frames to suit the box fan and furnace filters, and position over opposite vent openings.

The fan can be operated by an extension cord to an outlet, or it can be wired permanently using flexible armored conduit.