California Code of Regulations (Cal. Code Regs.): Title 24 – California Building Standards Code > Cal. Code Reg. §3120B.16 Turn on before entering.
Where automatic gaseous chemical feeders are used, a sign shall be posted at the switch to the light and ventilation system for the gaseous chemical feeder room stating, “TURN ON BEFORE ENTERING,” or as otherwise required by the California Fire Code or the California Electrical Code.