When were smoke detectors required to be hard wired. A condo assn. just called and told me that the bldg. dept found about 60 units that had combo smokes that were working on battery alone. Several years ago the assn paid to have SDs installed in the bedrooms, the installer took out a permit, ($15,000) but did not connect all of them hard wired. Now the bldg. dept wants them connected and new permits for each occupancy. Do they have to be interconnected between units?