Filming in locations that represent a city's underbelly such as abandoned buildings, shooting galleries and closed factories, is not only romantic, it's dangerous. Renovating and working in old armories, piers, warehouses and other venues large enough to accommodate filming, set construction and shops also can be hazardous. Even well-maintained public buildings and schools can be unsafe locations under certain conditions.
Any location can harbor biological, chemical, structural and safety hazards.
Cleaning up, repairing, or renovating in the presence of some of these hazardous conditions can only be done safely and legally by specially trained or certified workers. And certain jobs require professional surveys and laboratory tests be done. Obviously, producers have to pay for these tests and services. If your producers are the kinds of employers who recognize the hazards and are willing to pay for tests, talk to them. If not, call the union.