2006 New York Code - Exit And Directional Signs.

 
    §  56.  Exit  and  directional  signs.  Every means of egress shall be
  indicated by a sign reading "EXIT" in red letters at least eight  inches
  high  on  a  white  background,  or vice versa, illuminated at all times
  during the day and night by a red light of at least twenty-five watts or
  equivalent illumination.  Such light shall be maintained  in  a  keyless
  socket.  On  all  stories  where  doors,  openings or passageways giving
  access to any means of egress are not visible from all portions of  such
  stories, directional signs shall be maintained in conspicuous locations,
  indicating in red on a white background, or vice versa, the direction of
  travel  to  the  nearest  means  of  egress.  At least one sign shall be
  visible from the doorway of each room or suite of rooms. Existing  signs
  and  illumination  may be accepted if, in the opinion of the department,
  such existing signs and illumination serve the  intent  and  purpose  of
  this  section.   Supplementary stairs, fire-stairs or fire-escapes which
  do not lead to the entrance story or to a street or to a yard or  court,
  leading  to  a  street,  shall  be clearly marked "NOT AN EXIT" in black
  letters at least four inches high on a yellow  background,  and  at  the
  termination  of  each such stair, fire-stair or fire-escape, there shall
  be a directional sign indicating the nearest means of egress leading  to
  a  street.  All signs shall be constructed, located and illuminated in a
  manner satisfactory to the department.