Except as provided in subsection (b) of this section, if there is clear evidence that an exception will not adversely affect the fire safety of a building or its occupants, the State Fire Marshal or a local authority with jurisdiction over the enforcement of fire and building codes may grant an exception to: a requirement of a State or local fire and building code if a sprinkler system is installed in a building as required by this subtitle; or the sprinkler system requirement of this subtitle if, on or before June 30, 1990: the local authority gave approval to a construction plan for a dormitory, hotel, lodging or rooming house, multifamily residential unit, or town house; and the approved plan did not include the installation of a sprinkler system as required by this subtitle. The State Fire Marshal or a local authority may not grant an exception under this section to a smoke detector requirement.