Not An Exit Sign
This Not An Exit Sign uses safety messages for emergency response protocol and compliance. A Not An Exit Sign is a useful device to help protect the health and safety of personnel, but is not an alternative for required protective measures for eliminating or abating hazards.
OSHA 1910.37(b)(5):
Each doorway or passage along an exit access that could be mistaken for an exit must be marked "Not an Exit" or similar designation, or be identified by a sign indicating its actual use (e.g., closet).