Section 39(5)(b) in The Merchant Shipping (Fire Appliances) Rules, 1969
(b)Notwithstanding the requirement of Cl. (a), portable dry powder fire extinguishers wherein the substance to extinguish fire is stored under pressure may be provided in compliance with these rules in either the accommodation or service spaces or in the machinery spaces, subject to their number not exceeding one half of the total number of extinguishers required to be provided in either of these spaces.