[GH85Carrera]

Back in the olden days when I worked at a place called Pro Photo, which was a professional photo lab we had a few fun things to do to newbies. THE number one rule at any photo lab is never open a door, unless you are willing to bet your next paycheck that no one is is in the darkroom with light sensitive material out. If you go barging into a darkroom and open the door and fog the material in there it can be very expensive.

If the door is closed, it is likely someone closed it for a reason. The door to the paper processor was a double door so as long as the inside door was closed it did not fog anything. If I was in there putting paper on the processor and they pound on the door out in the room light I would yell DARK! and and meant don't come in. If it was safe and there was nothing to fog, I yell SAFE! and they know to come in and I am likely coming out.

If I am back there putting on paper and they just walk in, and to double door protected everything they got lucky. But walking into a room that is 100% dark as a cave at midnight they can't see anything at all. My eyes are accustomed to the dark so I can see the glow tape spots that outline the back of the processor and I can tell where they are. I would not say a thing, just quietly walk over next to them and firmly grab them by the arm, and say YOU FORGOT TO KNOCK! They usually jumped a foot or so and, often screamed but they never forgot to knock again. When a firm hand grabs you on a room that you think is empty, it gets your attention.