The Coast Guard Office of Design and Engineering Standards has released Marine Safety Alert 05-22, to inform the Coast Guard Officers in Charge, Marine Inspection (OCMI) and the maritime industry that double block and bleed systems design, installed and operated in accordance with 74 SOLAS (14) II-2/5.5 are authorized under 46 CFR § 32.53-10(b) without the need for approval from the Coast Guard Marine Safety Center (MSC).
Source: USCG
Link: MSIB: Acceptance of IMO code for fire safety systems for tank vessel inert gas systems – double block and bleed non-return device