With reference to a machinery space carbon dioxide smothering system: (a) state the regulation regarding the rate of flooding with respect to time; (4) (b) state the precautions to be taken before activating the system. (6)
(a) Regulation regarding the rate of flooding with respect to time (4 marks)
SOLAS requires that a machinery space fixed CO₂ system must be capable of discharging not less than 85% of the required CO₂ charge within 2 minutes.
This ensures a rapid build-up of concentration to around 35% by volume, reducing oxygen levels quickly enough to extinguish the fire.
The system must be arranged so that CO₂ reaches all parts of the protected space uniformly.
(b) Precautions before activating the system (6 marks)
Raise the fire alarm and warn all personnel.
Stop all machinery (main engine, auxiliaries, pumps) to prevent damage and avoid drawing in fresh air.
Shut down ventilation – close all fans, dampers, skylights, doors, and other openings to seal the space.
Confirm personnel evacuation – conduct a headcount to ensure no one remains inside the protected area.
Isolate fuel sources – stop fuel pumps and close quick-closing valves on oil tanks.
Follow operating procedure – ensure chief engineer/master authorises discharge; operate the release valves in correct sequence.
