Perc is mostly a problem as a Ozone reducing chemical. It is used in Motiion picture wet gate printing, where it hides film base scratches as it has almost the same index of refraction as the film base.

The movie folks will rewash Film to get rid of emusion side scratches, but the total wet time is much less than an Hour. I understand that some labs will just rerun the ECN-2 process for colour negatives, and run B&W through their B&W negative process. (running B&W through B&W reversal or ECN-2 would be a disaster of course.)

The ozone wory means that the Perc vapor should be trapped so that it does not get anywhere near where you might breathe, or out into the atmosphere. Carbon Tet was a REAL poison.