With reference to the use of a CO2 flooding system: (a) list the precautions that should be taken before releasing CO2 into the machinery spaces of a vessel;(4) (b) state the length of time that should be allowed to elapse before re-entry into the machinery spaces can be considered, following release of CO₂;(2) (c) state the precautions that should be taken before the machinery space can be safely re-entered, following release of CO₂. (4)
(a) Precautions before releasing CO₂ into machinery spaces (4)
Raise the alarm – warn all crew onboard of imminent CO₂ release.
Evacuate personnel – ensure the machinery space is completely clear of crew.
Stop all ventilation and close dampers – to prevent CO₂ leakage and ensure effective concentration.
Close all openings (doors, skylights, funnels, ventilators) – to keep the space sealed and allow CO₂ to build up to the required concentration.
(b) Time before re-entry after CO₂ release (2)
A minimum of 24 hours should elapse before re-entry is considered safe, unless gas-free testing confirms that the atmosphere is safe earlier.
This allows CO₂ to settle and ensures the fire is fully extinguished.
(c) Precautions before re-entering the machinery space (4)
Test the atmosphere using approved portable gas detectors to confirm safe oxygen levels.
Ventilate thoroughly by restarting fans and opening dampers only after clearance is given.
Wear self-contained breathing apparatus (SCBA) if entry is required before full gas-free certification.
Obtain permission from the Master/Chief Engineer and ensure a standby rescue team is present.
