Found hanging heaters and wash bay 30 feet in the air, both running when arrived found flue pipe, broken at wall penetration. Was able to remove pipe and reattach pipe together properly preventing flu gases from entering into the wash bay. Tech in wash bay stated heaters work until bay doors are opened. All heat will stay high being heat rises when bay door are open to the elements Showed customer heaters running with temp gun readings. Had customer sign ticket and returned to service