The height limitations of this chapter shall not apply to church spires, belfries, cupolas, domes not suitable for human occupancy, chimneys, ventilators, skylights, water tanks, bulkheads and necessary mechanical appurtenances usually carried above the roof level or to noncommercial radio and television antennas, except where, in the opinion of the Zoning Board, such may be deemed to interfere with aerial navigation or constitute a fire hazard.