N.Y.C. Admin. Code § 27-499: § 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.