Uh, yes. Let him in, get it done, get it over with.
First I don't believe a mask provides much protection, but why not just stay a certain distance from the guy, like six feet? That seems to be the magic number for some reason.
Someone is doing the plumbing work I assume, but thats somehow OK because they are wearing masks? The math doesn't work.
If they're really friggin paranoid they could spray lysol over hell and creation afterward.