9.3.4 Termination of Vent Pipe Outlets
9.3.4(a) Termination on weather deck. Outlets of vents from the following tanks are to be led to the weather:
• Ballast tanks
• Fuel-oil tanks, except fuel-oil drain tanks with a volume less than 2 m3 (70.6 ft3) and which cannot be filled by a pump – see 4-6-4/13.3.4
• Thermal oil tanks
• Tanks containing liquids having flash point of 60°C (140°F) or below
• Void tanks adjacent to tanks containing liquids having a flash point of 60°C or below
Where it is impracticable to terminate vents on a weather deck as required, vents may be led overboard from a deck below the weather deck. In such a case, non-return valves of an approved type are fitted at the outlets to prevent ingress of water. See also 4-6-4/9.5.3.