5.5.1 Permanently installed gas detectors should
be fitted in the tank room, in all ducts around gas pipes, in machinery
spaces of the ESD-protected type, compressor rooms and other enclosed
spaces containing gas piping or other gas equipment without ducting.
In each ESD-protected machinery space, two independent gas detector
systems should be required.
5.5.2 The number of detectors in each space should
be considered taking size, layout and ventilation of the space into
account.
5.5.3 The detection equipment should be located
where gas may accumulate and/or in the ventilation outlets. Gas dispersal
analysis or a physical smoke test should be used to find the best
arrangement.
5.5.4 An audible and visible alarm should be activated
before the vapour concentration reaches 20% of the lower explosion
limit (LEL). For ventilated ducts around gas pipes in the machinery
spaces containing gas-fuelled engines, the alarm limit can be set
to 30% LEL. The protective system should be activated at a LEL of
40%.
5.5.5 Audible and visible alarms from the gas
detection equipment should be located on the bridge and in the engine
control room.
5.5.6 Gas detection for gas pipe ducts and machinery
spaces containing gas-fuelled engines should be continuous without
delay.