.-(1) Before any petroleum is discharged from a ship or vessel, the holds of such vessels shall be thoroughly ventilated:Provided that nothing in this sub-rule shall apply to any vessel carrying petroleum Class A not exceeding 30 litres or petroleum Class B not exceeding 2,500 litres or petroleum Class C.(2)After all petroleum has been discharged from any such vessel, the holds, tanks and bilge's of the vessel shall be rendered free from inflammable vapour.(3)Sub-rule (2) shall not apply to the tanks of a ship importing petroleum which leaves the port without delay after unloading of cargo or remains only for the purpose of taking on board bunkers, stores or ballast or for such other purpose as may be approved by the Conservator, if the tanks of every such ship are securely fastened down immediately after the discharge of the cargo.(4)Sub-rule (2) shall not apply to barges or lighters continuously engaged in the transport of petroleum in bulk, if-(a)an interval of not more than 72 hours is likely to elapse between an operation of unloading and the next loading operation; and(b)the tanks are securely fastened down immediately after unloading.(5)Sub-rule (2) shall not apply to specially constructed steel tank motor vessel approved by the Chief Controller which are engaged in the transport of petroleum in bulk on such rivers and on such ports thereof as may be approved by him in areas outside port limits, or by the Conservator within port limits, if the tanks of such vessels are securely fastened down immediately after unloading and the vessels depart not later than 12 hours after completion of unloading for their next place of loading.(6)All ships or other vessels which by sub-rule (3) or sub-rule (4) or sub-rule (5) are exempted from the application of sub-rule (2) shall until their holds and tanks have been rendered free from inflammable vapour, comply with all the rules applicable to ships or other vessels when carrying petroleum in bulk.
