No sign shall be so placed as to obstruct or interfere with any exit way or so as to prevent free passage from one part of a roof to any other part thereof, or so as to interfere with light and ventilation, or so as to obstruct any opening in an exterior wall required for Fire Division access, nor obstruct or be attached to any fire escape. No sign shall be supported from the sidewalk, street or alley. (Ord. 8904. Passed 12-9-57.)