Are you building or remodeling a darkroom? Here are some things to keep in mind. Many artifacts can show up on processed films because of dirty darkrooms. Lint and dust can be transferred from the counter or processor feed tray into the processor and then stick to the rollers causing marks on the films. Frequently MDH finds inappropriate safe lights or white light leaks. Beyond routine, frequent cleaning of the darkroom, and the required fog tests the following items will help to eliminate problems.

Require a solid ceiling not a "dropped tile" or acoustical tile ceiling. With a tile ceiling, every time the door opens and closes ceiling tiles move and dust particles from the tile edges rain down. In addition, ceiling tiles often have holes in them that can admit light from a crawl space above.
Do not put open shelving above the counter, they collect to much dust. If you store items there, they will shed dust when items are moved.
Avoid putting the room vent above the counter or feed tray if at all possible. Have a scheduled, frequent cleaning of the vent. Ensure that no light is coming from the vent.
Safelights need to be a minimum of four feet from the work counter. A frosted bulb of no more than 15 watts is permitted at four feet. Ensure that you have the correct safelight filter for the film you use. Just because it is red, does not mean that it is safe.
Walls and counter tops do not have to be black or dark. Light walls will help reflect the safelighting making it easier to see.
Do not use fluorescent lighting. The afterglow from some fluorescent bulbs is enough to fog x-ray film.
Ensure that no light is coming through the door edges, around the processor or around the passboxes.
Never store film on the floor.
The processor dryer should be vented to the outside. This not only reduces the chemical smell to the room, but also diverts the fumes and humidity that can damage parts inside of the processor and or cause artifacts.