Section 40(6) in The Merchant Shipping (Fire Appliances) Rules, 1969
(6)When carbon dioxide is used as an extinguishing medium--(i)if discharged into space containing boilers or internal combustion type of machinery, the quantity of gas available shall be sufficient to give a minimum quantity of free gas to larger of the following quantities, namely, either---------a volume to include the casing tip to the level at which the(a)40 per cent of the gross volume of the largest space, such horizontal area of the casing is 40 per cent or less of the space concerned; or(b)35 per cent of the entire volume of the largest space including the casing :Provided that the above mentioned percentages maybe reduced to 35 per cent or 30 per cent, as the case may be, in the case of cargo ships of less than 2000 tons :Provided further that if two or more spaces containing boilers or internal combustion type of machinery are not entirely separate, they shall be deemed as forming one compartment;(ii)if discharged into cargo spaces, the quantity of gas available shall be sufficient to give a minimum volume of free gas equal to 30 per cent of the gross volume of the largest cargo compartment in the ship which is capable of being sealed;(iii)if discharged into both cargo spaces and spaces containing boilers or internal combustion type of machinery, the quantity of gas need not be more than the maximum required either for the largest cargo compartment or machinery spaces;(iv)if discharged into spaces containing boilers or internal combustion type of machinery, the fixed piping system shall be such that 88 per cent of the gas shall be capable of being discharged into such spaces within two minutes.
