Every state has it’s own laws dictating the regulations and requirements for buildings to use exit signs. However there are some general guidelines to follow that will get you most of the way to code compliance.

• Place in an easy to view location with no viewing obstructions

• Place above every exit

• Place in halls and corridors at every turn or angle.

• Use signs with arrows in halls and on walls.

• Mark doorways that are not exits

Check out exit signs that meet California code or read the code here:

Subchapter 7. General Industry Safety Orders
Group 1. General Physical Conditions and Structures Orders
Article 2. Standard Specifications

(a) Luminance. Exit and directional signs shall have a luminance on the face of such signs of not less than 50 lux. The words used on such signs shall be in block letters at least 6 inches in height with a stroke of not less than 3/4 inch. Exception: Existing signs may have the word “EXIT” in lettering not less than 5 inches high with principal strokes of letters of not less than 1/2 inch. Letters shall be of such color or design as to be in strong contrast to the background of the sign. Arrows or other directional symbols shall be of equal visibility to that stipulated herein for letters.

(b) Location. Exit or directional signs, or both, shall be provided at every exit door, at the intersection of corridors, at exit stairways or ramps and at such other locations and intervals as are necessary to provide the occupants with knowledge of the various means of egress available. Exit or directional signs need not be provided for the following:

(1) Any room or building having an occupant load of 50 or less;

(2) Dwellings units in Group R, Division 1 Occupancies;

(3) When approved, the main exterior exit doors obviously and clearly identifiable as exits. (Title 24, Part 2, Section 2-3312(c)(3).)

(c) Electrically Illuminated Signs. Exit and exit directional signs which are required to be electrically illuminated shall be lighted with two electric lamps, either one of which shall be sufficient to provide the required luminance on the face of the sign. NOTE: Radioactive isotope self powered signs with a luminance of not less than 0.02 lamberts during its useful life will be acceptable.

(Title 24, Part 2, Section 2-3312(c)(2).)

Source: http://www.dir.ca.gov/Title8/3216.html

You can get New York approved exit signs online that meet all code requirements; if you want to read the New York exit sign code then here it is:

ADC New York City Administrative Code - ARTICLE 7 - Exit Signs and Other Markings

§ 27-383 Requirements. (a) Exit signs. Except in occupancy groups J-2
and J-3, the location of every exit on every floor and every opening
from a room classified in occupancy group J-1 and containing cubicles
shall be clearly indicated by exit signs. Such signs shall be placed at
an angle with the exit opening if such placement is required for the
signs to serve their purpose. In long corridors, in open floor areas,
and in all other situations where the location of the exit may not be
readily visible or understood, directional signs shall be provided to
serve as guides from all portions of the corridor or floor.
(b) Exit path markings in high rise office buildings and in occupancy
group E high rise buildings. On and after July 1, 2006 all high rise
office buildings and all high rise buildings classified in occupancy
group E shall have exit path markings conforming to this subdivision.
This provision shall be retroactive and shall apply to buildings
constructed on and after such date and to buildings in existence on such
date. All exit path markings required herein shall be of an approved
photoluminescent material. The markings shall be washable, non-toxic,
non radioactive, and if subjected to fire must be self extinguishing
when the flame is removed.
(1) All doors opening to corridors, to an exit, or to an exit
passageway, shall be marked with the word “exit”.
(2) Within exit stairs, horizontal extensions in exit stairs,
horizontal exits, supplemental vertical exits and exit passageways,
except within street level lobbies, there shall be directional markings.
(3) Required markings for exit paths shall comply with the technical
standards for installation and placement to be set forth in a reference
standard. Such reference standard shall be designated RS 6-1 and shall
be adopted on or before January 1, 2006.

§ 27-383.1 Additional requirements for high rise office buildings and
occupancy group E high rise buildings. In high rise office buildings and
in occupancy group E high rise buildings:
(a) Illuminated exit signs complying with section 27-386 of this
subchapter shall be placed in stairwells with horizontal extensions to
indicate the transition from vertical to horizontal direction and at
turns along the horizontal path.
(b) A supplementary sign complying with sections 27-394 and 27-395 of
this subchapter, except that the lettering and numerals shall be at
least one inch high, indicating the location of a recessed re-entry
door, shall be securely attached on the wall of the landing that faces
the evacuee on the stairs.
(c) In stairs where there is no entry or exiting from such stair for
more than four floors, a sign complying with sections 27-394 and 27-395,
except that the lettering and numerals shall be at least one inch high,
shall be securely attached at the beginning of the descent into such
portion of the stair on the wall of the landing that faces the evacuee
on the stairs stating the location of the next re-entry or exiting
floor. On each floor within such portion of the stair a sign complying
with sections 27-392 and 27-395 shall be securely attached to the wall
of the landing that faces the evacuee on the stairs approximately five
feet above the floor indicating the floor number.
(d) Signs shall be readily visible from the egress direction.
(e) High rise office buildings and high rise buildings classified in
occupancy group E in existence on the effective date of this section
shall comply with this section on or before July 1, 2007. For the
purpose of this section, a high rise building shall be deemed to be in
existence on the effective date of this section if on such effective
date it is complete or under construction or where an application for
approval of plans was filed with the department prior to such effective
date and construction commenced within two years after such effective
date.

Source: http://public.leginfo.state.ny.us/menugetf.cgi