NFPA 12 interpretation for CO2 supression

[nucleareng78]

CO2 suppression skids come with a lockout valve on the main CO2 discharge line but not on the pneumatic horn. I understand the pneumatic horn is fed by CO2 to warn those in the enclosure CO2 is present prior to releasing the main isolation valve discharging CO2 (time delayed valve).

NFPA 12 states that lockout valves should be supplied where CO2 could migrate, creating a hazard to personnel. However when the system is locked out and a worker is performing maintenance he/she can still be exposed to CO2 through the pneumatic horn being activated. I would like to place a manual isolation valve on the pneumatic line to positively isolate the CO2 skid such that there is no chance of CO2 exposure (aside from a leaking valve) while the system is locked out.

Is this still code compliant since NFPA 12 is silent on distinguishing if the pneumatic horn line must be available during a system outage?

 

[cdafd]

More than likely does not meet NFPA or manufacture listing

Have you talked to the manufacture??