Section 39(9) in The Merchant Shipping (Fire Appliances) Rules, 1969
(9)A spare charge shall be provided for every portable fire extinguisher provided in compliance with these rules, except that for each such fire extinguisher which is of a type that cannot readily be recharged while the ship is at sea, an additional portable fire extinguisher of the same type, or its equivalent, shall be provided in lieu of a spare charge.
