Gaseous extinguishing systems

Yes — Under 1910.162(a)(1) this section applies to all fixed extinguishing systems that use a gas as the extinguishing agent when they are installed to meet a particular OSHA standard, and those systems must also comply with 1910.160.

• The gas used as the agent may be in a liquid state during storage, but the system is regulated as a gaseous extinguishing system under this section.
• Employers should also review 1910.160 for complementary requirements referenced by 1910.162(a)(1).

Answer: Paragraphs (b)(2) and (b)(4) through (b)(6) apply only to total flooding systems as stated in 1910.162(a)(2).

• That means requirements like maintaining designed concentration (b)(2), required discharge timing (b)(4), pre-discharge alarms (b)(5), and Halon 1301 egress/concentration limits (b)(6) are specific to total flooding installations.
• For local application/stream systems, other paragraphs in 1910.162 still apply.

No — Carbon dioxide obtained by converting dry ice to liquid is not acceptable unless it is processed to remove excess water and oil; otherwise, agents must be the type approved for the system's application per 1910.162(b)(1).

• Use only agents specifically approved for the system and application by the system manufacturer or applicable listing/approval authority.
• If liquid CO2 comes from dry ice conversion, it must be processed to remove water and oil before being used.

Yes — The employer must assure that the designed concentration of gaseous agents is maintained until the fire has been extinguished or is under control, except during overhaul, according to 1910.162(b)(2).

• "Except during overhaul" means concentrations may be allowed to vary while overhaul operations are underway, but during active suppression they must meet the designed level.
• Employers should have procedures to confirm the system achieves and maintains design concentration during a fire.

Answer: The employer must assure that employees are not exposed to toxic levels of the gaseous agent or its decomposition products as required by 1910.162(b)(3).

• This requires employers to evaluate hazards from the agent and any products formed by heat or decomposition, and to take steps (engineering controls, procedures, monitoring, PPE, training) to prevent employee exposure above safe levels.
• Keep records and procedures that show how exposures are assessed and controlled.

Answer: The employer must assure that the designed extinguishing concentration is reached within 30 seconds of initial discharge for most gaseous systems, except Halon systems which must achieve design concentration within 10 seconds, according to 1910.162(b)(4).

• Test and adjust piping, nozzles, and storage so the system meets these timing requirements for its listed design.
• These timing requirements apply to total flooding systems per 1910.162(a)(2).

Answer: A distinctive pre-discharge employee alarm is required when agent design concentrations exceed the maximum safe level for employee exposure, and specific thresholds require a pre-discharge alarm for Halon 1211 and carbon dioxide systems with a design concentration of 4 percent or greater and for Halon 1301 systems with a design concentration of 10 percent or greater, as stated in 1910.162(b)(5).

• The alarm must be capable of being perceived above ambient light or noise levels and must provide employees time to safely exit the discharge area prior to system discharge.
• Employers should document alarm placement, audibility/visibility testing, and evacuation procedures so employees can exit safely when the alarm sounds.

Answer: Halon 1301 concentration limits depend on how long it takes employees to escape: do not use concentrations greater than 7% where egress cannot be accomplished within one minute; do not use concentrations greater than 10% where egress takes greater than 30 seconds but less than one minute; and concentrations greater than 10% are permitted only in areas not normally occupied provided employees can escape within 30 seconds and no unprotected employees enter during discharge, per 1910.162(b)(6)(i)-(iii).

• Employers must evaluate evacuation times and choose Halon 1301 concentrations that comply with these limits.
• When using >10% Halon 1301 in unoccupied areas, employers must ensure controls prevent unprotected entry during discharge.

No — The pre-discharge alarm must be "distinctive" and "capable of being perceived above ambient light or noise levels," which allows either audible or visible (or both) alarms depending on the workplace, according to 1910.162(b)(5).

• Choose alarm types (audible, visual strobes, voice evacuation, etc.) that are effective given ambient noise and lighting conditions.
• Test alarms regularly to ensure they are perceivable and provide sufficient time for safe evacuation.

No — Except during overhaul, the employer must assure that the designed concentration is maintained until the fire has been extinguished or is under control, per 1910.162(b)(2).

• Reducing concentration before the fire is controlled could allow re-ignition or expose employees to hazards and would not comply with the standard.
• During overhaul (post-extinguishment activities), deviations from design concentration are contemplated, but employers should follow procedures to protect personnel.

No — Employers may not use carbon dioxide obtained by dry ice conversion to liquid unless it is processed to remove excess water and oil, as stated in 1910.162(b)(1).

• Untreated CO2 from dry ice conversion can carry contaminants that damage system components or create hazards.
• Use only properly processed CO2 or agents approved for the specific system application.

Yes — The standard explicitly notes that in some cases the gas may be in a liquid state during storage, and such systems are covered under 1910.162(a)(1).

• Employers should treat storage-phase liquids according to the system manufacturer's instructions and applicable requirements in 1910.160 and 1910.162.

No — Halon 1301 concentrations greater than 10% are only permitted in areas not normally occupied, and then only if any employee in the area can escape within 30 seconds and the employer assures that no unprotected employees enter the area during agent discharge, as required by 1910.162(b)(6)(iii).

• For normally occupied areas, maintain concentrations at or below the applicable limits tied to egress times in 1910.162(b)(6).
• Employers must implement access controls and procedures to prevent unprotected entry during discharge in unoccupied spaces with >10% Halon.

Answer: It means the pre-discharge alarm must give enough advance warning so employees can leave the discharge area before the agent is released, as required by 1910.162(b)(5).

• Employers must evaluate actual exit routes and times for their workplace and configure alarm timing and procedures so employees can evacuate safely.
• Documented drills, posted evacuation routes, and clear procedures help demonstrate the alarm provides sufficient egress time.

No — The timing requirement in 1910.162(b)(4) (30 seconds, or 10 seconds for Halon) applies only to total flooding systems as specified by 1910.162(a)(2).

• For local application or streaming systems, employers should follow system listings and manufacturers' guidance and ensure adequate performance but are not bound by the total-flooding timing limits in (b)(4).
• Always verify which paragraphs of 1910.162 apply to the installed system per 1910.162(a)(2).

Yes — 1910.162(b)(5) specifically requires a pre-discharge employee alarm for Halon 1211 systems with a design concentration of 4 percent or greater and for Halon 1301 systems with a design concentration of 10 percent or greater, in addition to the general requirement when agent concentrations exceed maximum safe levels, as stated in 1910.162(b)(5).

• Even if a system’s concentration does not exceed general maximum safe levels, these thresholds for Halon 1211 and 1301 trigger the pre-discharge alarm requirement.
• Employers should treat Halon systems with particular attention to alarm timing and escape procedures.

Answer: Employers must assure that no unprotected employees enter the discharge area during agent discharge, particularly where high concentrations are used (see 1910.162(b)(6)(iii)), and must provide alarms and controls per 1910.162(b)(5).

• Practical steps include access control (locked/latched doors), visible warning signs, alarmed entry points, supervised entry procedures, and training so employees know to stay clear during discharge.
• Documenting these controls and testing them regularly helps demonstrate compliance.

Yes — Halon systems must achieve the design concentration within 10 seconds of initial discharge, while other gaseous total-flooding systems must achieve it within 30 seconds, according to 1910.162(b)(4), which applies to total flooding systems per 1910.162(a)(2).

• System design, piping, and nozzle selection must ensure these timing requirements are met during commissioning and maintenance testing.

Answer: Employers must assure employees are not exposed to toxic levels of the agent or its decomposition products per 1910.162(b)(3) and, when concentrations exceed safe levels, provide a pre-discharge alarm as required by 1910.162(b)(5).

• This typically requires hazard assessment, monitoring for decomposition byproducts after discharge (when applicable), PPE or respiratory protection if personnel must enter, and procedures limiting entry until the atmosphere is safe.
• Training and documented entry procedures for post-discharge and overhaul activities are essential to protect workers from toxic exposures.

Yes — Employers must ensure gaseous extinguishing systems installed to meet a particular OSHA standard also comply with related requirements, such as 1910.160 as referenced in 1910.162(a)(1), and should consult broader 1910 requirements as applicable.

• Systems often intersect with other standards (e.g., wiring, alarms, access control), so review the relevant parts of 1910 and 1910.160 when designing, installing, and maintaining extinguishing systems.
• Document compliance with all applicable sections and manufacturer instructions.