9.2.1 Interbarrier and hold
spaces associated with cargo containment systems for flammable gases
requiring full secondary barriers should be inerted with a suitable
dry inert gas and kept inerted with make-up gas provided by a shipboard
inert gas generation system, or by shipboard storage which should
be sufficient for normal consumption for at least 30 days.
9.2.2.1 Interbarrier and
hold spaces associated with cargo containment systems for flammable
gases requiring partial secondary barriers should be inerted with
suitable dry inert gas and kept inerted with make-up gas provided
by a shipboard inert gas generation system or by shipboard storage
which should be sufficient for normal consumption for at least 30
days.
9.2.2.2 Alternatively, subject
to the restrictions specified in chapter 17,
the Administration may allow the spaces referred to in 9.2.2.1 to be filled with dry air provided
that the ship maintains a stored charge of inert gas or is fitted
with an inert gas generation system sufficient to inert the largest
of these spaces; and provided that the configuration of the spaces
and the relevant vapour detection systems, together with the capability
of the inerting arrangements, ensure that any leakage from the cargo
tanks will be rapidly detected and inerting effected before a dangerous
condition can develop. Equipment for the provision of sufficient dry
air of suitable quality to satisfy the expected demand should be provided.
9.2.3 For non-flammable gases,
the spaces referred to in 9.2.1 and 9.2.2.1 may be maintained with a suitable
dry air or inert atmosphere.
9.2.4 In case of internal insulation
tanks, environmental control arrangements are not required for interbarrier
spaces and spaces between the secondary barrier and the inner hull
or independent tank structures completely filled with insulation materials
complying with 4.9.7.2.