2006 New York Code - Obstructions.

 
    § 27-499 Obstructions. No sign shall be erected so as to obstruct free
  ingress  to,  or  egress from, a required door, window, stairs, or other
  required exits, or be placed so as to prevent free passage from one part
  of a roof to any other part. No sign shall be attached in any manner  to
  a  fire  escape or exterior stair, or placed so as to interfere with any
  opening for light  or  ventilation  required  under  the  provisions  of
  subchapter twelve of this chapter.