Studios have fire lane laws for safety. In the event of a fire, and limited vision, a person ought to be able to feel their way around the perimeter of the stage, and be able to safely escape without obstruction. Here, it varies from 4-5 feet. There have been many times when I have had to place sets closer together than I would have liked to, but I had to adhere to the regulations.
On one show, I was working with a 'think-outside-the-box' Designer. We had a studio that was just perfect for our set: it had a nice big opening. We needed to build a set with a practical exterior. In essence, we sandwiched the building entrance wall between the interior set and the exterior facade, so that we could build our own practical entrance.
But the set would have to cross over and block the fire lane. As it turned out, as long as we had a standard fire size door over the fire lane, the Fire Chief could pass the inspection.
We made them into "FIRE EXITS"