Rule 31. If an inert gas or foam system is provided in an occupied area for the prevention or extinguishment of fire or explosion, then the affected area shall be conspicuously posted to call attention to the potential creation of a nonrespirable atmosphere. The actuating of an audible and visible alarm before the system is activated shall be provided. The system shall incorporate a sufficient time-delay to permit the egress of persons within the affected area. After the activation of the system, an audible and visible warning that a nonrespirable atmosphere has been created within the area shall continue until the nonrespirable atmosphere has been purged or diluted with air to safe breathing levels.
Mich. Admin. Code R. 325.2431