12.1.1 Electric motor rooms,
cargo compressor and pump rooms, other enclosed spaces which contain
cargo handling equipment and similar spaces in which cargo handling
operations are performed should be fitted with mechanical ventilation
systems capable of being controlled from outside such spaces. Provision
should be made to ventilate such spaces prior to entering the compartment
and operating the equipment and a warning notice requiring the use
of such ventilation should be placed outside the compartment.
12.1.2 Mechanical ventilation
inlets and outlets should be arranged to ensure sufficient air movement
through the space to avoid the accumulation of flammable or toxic
vapours and to ensure a safe working environment, but in no case should
the ventilation system have a capacity of less than 30 changes of
air per hour based upon the total volume of the space. As an exception,
gas-safe cargo control rooms may have eight changes of air per hour.
12.1.3 Ventilation systems
should be fixed and, if of the negative pressure type, permit extraction
from either the upper or the lower parts of the spaces, or from both
the upper and the lower parts, depending on the density of the vapours
of the products carried.
12.1.4 In rooms housing electric
motors driving cargo compressors or pumps, spaces except machinery
spaces containing inert gas generators, cargo control rooms if considered
as gas-safe spaces and other gas-safe spaces within the cargo area,
the ventilation should be of the positive pressure type.
12.1.5 In cargo compressor
and pump rooms and in cargo control rooms if considered gas-dangerous,
the ventilation should be of the negative pressure type.
12.1.6 Ventilation exhaust
ducts from gas-dangerous spaces should discharge upwards in locations
at least 10 m in the horizontal direction from ventilation intakes
and openings to accommodation spaces, service spaces and control stations
and other gas-safe spaces.
12.1.7 Ventilation intakes
should be so arranged as to minimize the possibility of recycling
hazardous vapours from any ventilation discharge opening.
12.1.8 Ventilation ducts
from gas-dangerous spaces should not be led through accommodation,
service and machinery spaces or control stations, except as allowed
in chapter 16.
12.1.9 Electric motors driving
fans should be placed outside the ventilation ducts if the carriage
of flammable products is intended. Ventilation fans should not produce
a source of vapour ignition in either the ventilated space or the
ventilation system associated with the space. Ventilation fans and
fan ducts, in way of fans only, for gas-dangerous spaces should be
of nonsparking construction defined as:
-
.1 impellers or housing of nonmetallic construction,
due regard being paid to the elimination of static electricity;
-
.2 impellers and housing of nonferrous materials;
-
.3 impellers and housing of austenitic stainless
steel; and
-
.4 ferrous impellers and housing with not less than
13 mm design tip clearance.
Any combination of an aluminium or magnesium alloy fixed or
rotating component and a ferrous fixed or rotating component, regardless
of tip clearance, is considered a sparking hazard and should not be
used in these places.
12.1.10 Spare parts should
be carried for each type of fan on board referred to in this chapter.
12.1.11 Protection screens
of not more than 13 mm square mesh should be fitted in outside openings
of ventilation ducts.