Chimneys, spires, etc. The height limitations of this chapter shall not apply to belfries, church spires, cupolas, penthouses and domes which are not used for human occupancy; or to chimneys, ventilators, skylights, water tanks and necessary mechanical appurtenances usually carried above the roof level; or to flagpoles, monuments, transmission towers and cable, radio and television antenna or towers or satellite dishes and similar structures. Such features, however, shall be erected only to such height as is necessary to accomplish the purpose for which they are intended. No advertising device of any kind whatsoever shall be inscribed upon or attached to that part of any chimney, tower, tank or other structure which extends above the roof limitations.