Sketch description: The system comprises a bank of CO2 cylinders (high-pressure, ~50-60 bar) stored in a dedicated CO2 room (outside the protected space, e.g. on the main deck or a separate compartment), connected to a manifold. From the manifold, a main distribution pipe runs into the machinery space, branching into a network of pipes with discharge nozzles arranged to distribute the gas uniformly throughout the space (nozzles near the top and a pair near the bilge/bottom to extinguish fires at low level). The system has:

• A master valve (main control) and a section/quick-release valve on the manifold.
• A remote release control (a release cabinet/lever) at a control station outside the space, with a two-stage operation (first a "prepare/evacuate" alarm, then the discharge).
• A pressure gauge, a safety/relief valve, and non-return valves.
• The cylinders are connected to the manifold via flexible hoses with a pilot/operating valve; the release is by a pneumatic/hydraulic or mechanical lever that opens the pilot cylinders and the main valve.
• An alarm (audible/visual) and a warning light indicating the gas is being discharged; the space must be evacuated and sealed (ventilation, skylights, watertight doors closed) before discharge.

The master/control valve (the main release valve on the manifold) should be operated first (or the pilot/operating valve that opens the main valve), before the section/quick-release valve to the space. Reason: opening the main valve first ensures that the CO2 is available to the distribution system and that the discharge is controlled and complete; the section valve (to the space) is then opened to flood the space. Operating the section valve first could allow the gas to be released into the space before the main supply is ready, or could cause an uncontrolled/partial discharge. In practice the two controls are interlocked so that the main valve must be opened before the section valve, ensuring the full quantity is delivered to the space in the correct sequence and that personnel are not exposed to a partial/accidental discharge.

After a CO2 discharge, the space is dangerous (CO2 displaces oxygen; the atmosphere is oxygen-deficient and may contain toxic combustion products). Entry procedure:

• Do not enter until the space has been thoroughly ventilated and the atmosphere tested.
• Ventilate the space (open the ventilation, hatches, skylights) to remove the CO2 and combustion products; use the ship's ventilation and, if necessary, portable fans.
• Test the atmosphere with an oxygen meter (O2 must be at least 20.9% or the safe level) and a combustible gas indicator (LFL) and, where relevant, a toxic gas detector; the space must be gas-free and safe.
• Use the enclosed space entry procedure: obtain a permit to work, ensure the space is ventilated continuously, and use a trained attendant at the entrance; the entrant wears a breathing apparatus (BA) until the space is proven safe, and a lifeline is used.
• Only after the atmosphere is verified safe (O2 normal, no flammable/toxic gas) may personnel enter without BA; otherwise BA and the full entry precautions are used.
• The entry is supervised, and the space is continuously monitored; the CO2 system is isolated/locked out before entry so it cannot be re-discharged.
• First aid: if a person is overcome by CO2, remove them to fresh air, give artificial respiration/oxygen, and seek medical help.