OSHA General Industry Standards (29 CFR Part 1910) 1910.162: 1910.162 Fixed extinguishing systems, gaseous agent

Applies to all fixed extinguishing systems that use a gas as the agent (which may be stored as a liquid) and are installed to meet a particular OSHA standard; they must also comply with 1910.160. Paragraphs (b)(2) and (b)(4) to (b)(6) apply only to total flooding systems. Agents for initial supply and replenishment must be of the type approved for the application, and carbon dioxide made by converting dry ice to liquid is not acceptable unless processed to remove excess water and oil. Except during overhaul, the designed concentration must be maintained until the fire is extinguished or under control. Employees must not be exposed to toxic levels of the agent or its decomposition products. The designed extinguishing concentration must be reached within 30 seconds of initial discharge, except Halon systems, which must reach design concentration within 10 seconds. A distinctive pre-discharge employee alarm perceivable above ambient light or noise is required where design concentrations exceed the maximum safe level for employee exposure, and specifically on Halon 1211 and carbon dioxide systems with a design concentration of 4 percent or greater and Halon 1301 systems with a design concentration of 10 percent or greater, giving time to exit before discharge. Halon 1301 limits: where egress cannot be accomplished within one minute, concentrations may not exceed 7 percent; where egress takes more than 30 seconds but less than one minute, concentrations may not exceed 10 percent; concentrations greater than 10 percent are allowed only in areas not normally occupied where any employee can escape within 30 seconds, and no unprotected employee may enter during discharge. Non-mandatory Appendix A to Subpart L notes that super-saturated areas must be ventilated before re-entry without protective clothing and respirators, and that employers should learn the toxic decomposition products of agents such as Halon 1211 from the manufacturer.