46 CFR § 131.825
Fixed fire extinguishing system controls
April 15, 2021
Each control cabinet or space containing a valve or manifold for a fire extinguishing system must be distinctly marked in conspicuous red letters at least 2 inches high: “[CARBON DIOXIDE/HALON/CLEAN AGENT] FIRE APPARATUS”, as appropriate.
[USCG-2006-24797, 77 FR 33884, June 7, 2012]