Emergency Response Procedures for Ships Carrying Dangerous Goods (EmS Guide) in the supplement of IMDG Code recommends use of Fixed gas fire-extinguishing systems for dangerous goods fire when loaded under deck.

H-cylinder canisters containing argon gas for ...
H-cylinder canisters containing argon gas for use in extinguishing fire in a server room, without damaging equipment. The bright green shoulder of the H cylinders signals an inert gas. Red is used here for argon, but other colors are used for argon in various systems, which are not fully standardized across the world. (Photo credit: Wikipedia)

Fixed gas fire-extinguishing system is operated by opening the pilot cylinder which will then initiate opening of other cylinders thus flooding the machinery space, pump rooms or cargo space as required.

There are requirements in SOLAS for the concentration of gas for spaces to which it should be released for extinguishing fire.

Single release control  of Fixed gas fire-extinguishing systems pose a danger to crew and other personal on board due to which SOLAS Regulation II-2/10 para is amended by RESOLUTION MSC.256(84) adopted on 16 May 2008  by adding  new paragraph 4.1.5  which is quoted below

4.1.5   By the first scheduled dry-docking after 1 January 2010, fixed carbon dioxide fire-extinguishing systems for the protection of machinery spaces and cargo pump-rooms on ships constructed before 1 July 2002 shall comply with the provisions of paragraph 2.2.2. of Chapter 5 of the Fire Safety Systems Code”.