Before releasing the fixed CO₂ fire-extinguishing system, every effort must be made to ensure that the fire cannot be controlled by other means and that all personnel are safe.

1. Raise the Alarm

• Sound the general emergency alarm.
• Inform the Master and the bridge immediately about the fire.

2. Assess the Fire

• Confirm that the fire is serious and cannot be controlled using portable fire extinguishers or other fixed fire-fighting systems.
• Decide that the release of the fixed CO₂ system is necessary.

3. Stop Machinery

• Stop the main engine, if required.
• Stop all auxiliary engines, if it is safe to do so.
• Stop boilers, fuel oil purifiers, fuel pumps, and other machinery to eliminate possible sources of ignition.

4. Shut Off the Fuel Supply

• Operate the quick-closing valves on the fuel oil tanks.
• Stop all fuel transfer pumps and fuel booster pumps to prevent further fuel supply to the fire.

5. Stop Ventilation

• Stop all engine room supply and exhaust fans.
• Close all ventilation dampers, skylights, and funnel dampers to make the machinery space airtight and prevent the escape of CO₂.

6. Close All Openings

• Close all watertight doors, fire doors, engine room access doors, windows, and hatches.
• Ensure that the engine room is completely sealed.

7. Evacuate All Personnel

• Confirm that all personnel have left the engine room.
• Carry out a head count at the designated muster station to ensure no one remains inside.

8. Inform the Crew

• Announce that CO₂ is about to be released.
• Ensure that no person enters the machinery space once evacuation has been completed.

9. Release CO₂

• Operate the CO₂ release cabinet strictly in accordance with the manufacturer's instructions.
• Release the required quantity of CO₂ into the engine room.

10. Keep the Space Sealed

• After discharge, keep the engine room completely sealed to maintain the CO₂ concentration and prevent re-ignition.
• The space should remain closed for the required soaking period, normally at least 20 minutes or as specified in the ship's procedures (often longer).

Means Provided to Prevent Inadvertent Release of CO₂

To prevent accidental or unauthorized discharge of CO₂, the following safety arrangements are provided:

• The CO₂ release cabinet is kept locked.
• A two-step release arrangement is provided, usually involving the operation of a pilot cylinder followed by the main release valve.
• The operating lever is fitted with a safety pin or locking arrangement.
• A break-glass panel or sealed cabinet must be opened before the system can be operated.
• Operating instructions are clearly displayed near the release cabinet.
• Audible and visual warning alarms operate before CO₂ discharge.
• A time-delay device is provided to allow personnel sufficient time to evacuate the protected space.
• Mechanical interlocks prevent accidental operation of the system.
• The release controls are located outside the protected machinery space.
• The CO₂ system is subjected to regular inspection, testing, and maintenance to ensure its safe and reliable operation.

After CO₂ has been discharged, re-entry into the engine room should only be carried out in a controlled and safe manner.

1. Do Not Enter Immediately
   • Allow sufficient soaking time for the CO₂ to extinguish the fire completely and reduce the possibility of re-ignition.
2. Obtain Permission
   • Re-entry should only be made with the permission of the Master after assessing the overall situation.
3. Ventilate the Space Carefully
   • When it is considered safe, begin controlled ventilation using the exhaust fans in accordance with the ship's emergency procedures.
4. Test the Atmosphere
   • Before entry, test the atmosphere for:
     • Oxygen concentration
     • CO₂ concentration
     • Toxic gases, such as carbon monoxide (CO) and hydrogen sulphide (H₂S), where applicable.
   • Initial Entry
     • The first entry should be made only by a trained fire party wearing:
       • Self-Contained Breathing Apparatus (SCBA), and
       • Full protective clothing.
     • Maintain Communication
       • Maintain continuous communication with personnel outside the engine room.
       • Keep a rescue team on standby throughout the operation.
     • Inspect the Engine Room
       • Carefully check for:
         • Remaining hot spots
         • Re-ignition
         • Structural damage
         • Fuel leaks
         • Electrical hazards
       • Continue Boundary Cooling
         • Continue boundary cooling, if necessary, to prevent the fire from spreading or re-igniting.
       • Restore the Space
         • Once the engine room has been declared safe:
           • Restore normal ventilation completely.
           • Inspect all machinery and electrical equipment before restarting operations.
           • Record the incident in the appropriate logbooks.
           • Arrange for replenishment, inspection, and servicing of the fixed CO₂ fire-extinguishing system before the vessel sails.