3.1 The Convention permeability of 60% for cargo
spaces is too low for use with ro-ro cargo spaces. A value of 90%
should be assumed for ro-ro cargo spaces above the bulkhead deck.
3.2 When spaces below the bulkhead deck are appropriated
for the use of cargo, a permeability of 60% can be used only where
it is demonstrated that such spaces regularly contain cargo, other
than ro-ro cargo. Otherwise, a permeability of 95% should be assumed.
That is, the space should be treated as a void space.
3.3 When spaces are appropriated for the carriage
of liquids, a permeability value of 95% should be assumed, unless
such spaces are to be permanently filled with ballast in the form
of liquid. That is, the liquid should be used as “lock-in" ballast.