Sean, I've worked in and around clean rooms for years. They have a few tricks that you can use and some you can't. In a class 10,000 clean room (the number is so many particles of dirt a certain size in a cubic meter?), which is good for satellite assembly and the like, it is not that clean. These are huge rooms. People wear tyvek suits and booties and hair covers. Sometimes you vacuum your clothes. No paper. This is something you can do is to reduce paper. As cheap paper gets old it sheds. Those old boxes and such...get rid of them. All equipment going in is cleaned by wiping down and vacuuming. Air handlers have good filters on them. Floors and walls are washable. I've never done the flashlight test in one.
In cleaner clean rooms, such as class 1000 or 100, the air handling gets better. Full bunny suits for people. No perfumes. Air is changed every few minutes. I think some of these have grates instead of floors. And it is only really clean at the work surface level.
In my darkroom, I don't have any great air handling. Everything is washable and gets a wipe every few months. I try to reduce the junk that is in there. When I dry film, I leave the room so the dirt isn't stirred up. And no flashlights.
A photo teacher told me that he always closed his eyes when he was loading film --- so he didn't see the light leaking under the door. It's like that.