SOLAS Chapter II-2 — Fire Protection, Detection & Extinction

1. Fire Theory, Classes of Fire & Extinction Methods

Marine firefighting is governed by the statutory safety objectives of SOLAS Chapter II-2 and the technical specifications of the FSS Code. Shipboard fire containment is built upon thermodynamic principles: combustion is a self-sustaining exothermic chain reaction requiring fuel, oxygen, heat, and active free radicals (H^• and OH^•). Extinguishing systems work by eliminating at least one side of this chemical tetrahedron.

• 15% / 21% — minimum oxygen concentration to sustain combustion, against the 21% in air.
• 1,600× — the expansion of water into steam on vaporisation.
• 2,260 kJ/kg — the latent heat of vaporisation of water.
• ≥ 5 units — minimum portable extinguishers on ships of 1,000 GT and above.
• Classes A–F — the standard marine fire range.

Shipboard Fire Classifications (ISO / IMO Standard)

Class A: Solid Carbonaceous. Wood, paper, textiles, bedding, fiberglass. Extinguished primarily by water jet or spray to penetrate glowing embers and absorb latent heat.

Class B: Flammable Liquids. HFO, MGO, lube oil, paint, bilge residues. Extinguished by mechanical foam blanketing (AFFF), CO2 gas flooding, or DCP. Never use solid water jets (causes boiling liquid spread).

Class C: Flammable Gases. Methane (LNG), propane/butane (LPG), acetylene. First isolate gas source by closing manifold valves; extinguish residual flame with DCP. Never extinguish if gas flow cannot be cut off (explosion risk).

Class D: Combustible Metals. Magnesium, aluminum swarf, sodium, potassium. Requires specialized dry flux powders (e.g. TEC powder / copper powder); water causes violent hydrogen generation and steam explosions.

Warning — Electrical Fires: Extinction Safety Rule. Electrical fires are not categorized as an independent fuel class in ISO standards because electricity is an ignition source rather than a fuel. Always de-energise electrical equipment first by tripping the breaker at the MSB or local distribution board. Once isolated, fight the residual fire using non-conductive CO2 or DCP. Water or foam must never be sprayed on live electrical apparatus.

2. Portable & Semi-Portable Extinguishers

SOLAS Regulation II-2/10 and the FSS Code Chapter 4 dictate the design, distribution, testing, and reserve inventory of shipboard portable fire extinguishers. Every unit must be engineered for immediate deployment, fitted with a tamper-evident seal, and maintained within strict weight and capacity parameters.

• ≤ 23 kg — maximum gross weight.
• 9 to 13.5 litres — fluid volume capacity.
• ≥ 5 units — minimum carried on ships of 1,000 GT and above.
• 100% / 50% — the spare charge spares rule.
• ≥ 750 mm — CO2 mounting height.

Technical Specifications of Marine Portable Extinguishers

SOLAS Extinguisher Spare Charges Rule

• Onboard rechargeable types. For extinguishers capable of being recharged on board (e.g. water and foam cartridge types), ships must carry 100% spare charges for the first 10 extinguishers, and 50% spare charges for the remaining extinguishers (up to a statutory ceiling of 60 spare charges).
• Shore-recharge only types. For extinguishers that cannot be recharged at sea (such as high-pressure CO₂ bottles), complete spare extinguishers of identical capacity and type must be provided in lieu of spare charges on a 1:1 basis for the required percentage.

3. Fixed Systems & Detectors

Category A machinery spaces (spaces containing internal combustion propulsion, auxiliary machinery > 375 kW, or oil-fired boilers) with a volume of 500 m³ and above require a type-approved total flooding fixed gas extinguishing system (FSS Code Chapter 5) complemented by an independent, power-driven local application water mist (hypermist) system (FSS Code Chapter 7).

• 85% in ≤ 2 minutes — CO2 engine room discharge rate.
• ≥ 500 m³ — Category A local application mandate.
• 70 bar — hypermist high-pressure pump.
• 68°C / 79°C — standard sprinkler bulb trip temperatures.
• 2 detectors — cross-zone interlock trigger.

Comparison of Fixed Machinery Space Firefighting Systems

4. Fire Main, Inert Gas, Fire Plan & Muster List

The ship's fire main provides pressurized seawater throughout all accommodation decks, machinery spaces, and cargo decks. It is backed by an independent emergency fire pump (SOLAS II-2 Reg 10.2.2) and the standardized International Shore Connection, which allows shore municipal fire departments to inject pressurized water into the vessel's fire main regardless of national coupling thread types.

• ≥ 25 m³/h or 40% — emergency fire pump capacity.
• ≥ 12 m — throw of two simultaneous water jets.
• ≤ 8% O₂ — inert gas ceiling inside cargo tanks.
• 178 mm / 132 mm — shore connection flange outside diameter and bolt circle diameter.
• 4 × 19 mm — slotted flange bolt holes.

Statutory Fire Main & Emergency Pump Operation

Main Fire Pumps. Cargo ships ≥ 1,000 GT require at least two independently driven power fire pumps. Combined capacity must deliver statutory pressure while discharging two 12 m solid jets from farthest hydrants.

Emergency Fire Pump (EFP). Independently powered pump located outside Category A machinery space (typically in steering flat or forepeak). Capacity ≥ 25 m³/h or 40% of total main fire pump capacity; suction sea chest must be submerged at lightest ballast draft.

Fire Main Isolating Valves. Fitted in the fire main on weather deck and machinery boundaries. If engine room fire main ruptures, isolating valves close to allow the emergency fire pump to supply all deck hydrants uninterrupted.

Inert Gas Pressure Limits. Inert gas supplied to crude oil/product tankers must maintain O₂ ≤ 5% at the scrubber outlet and ≤ 8% by volume inside cargo tanks at all times, with deck water seal preventing backflow.

Emergency Fire Pump Blackout Commissioning Procedure

1. Isolate Machinery Space Boundary. Close the fire main isolating valve located outside the engine room casing to prevent loss of water through damaged pipes in the machinery space.
2. Verify Sea Suction Valve. Ensure the emergency fire pump sea chest suction valve is fully opened and discharge valve to the deck fire main is cracked open.
3. Engage Prime Mover. Start the independent prime mover (dedicated diesel engine with hydraulic/spring start, or electric motor fed directly from the Emergency Switchboard).
4. Confirm Priming & Discharge Pressure. Verify the water ring or vacuum ejector priming unit draws sea water; observe discharge pressure gauge rise steadily to at least 2.7 bar (cargo) or 3.2 bar (passenger).
5. Verify 12 m Deck Jets. Open two farthest weather deck hydrants with 12 mm nozzles attached; confirm two continuous solid jets of minimum 12-metre throw.

Oral Examination Viva Bank: SOLAS Chapter II-2

1. What are the exact statutory dimensions of the International Shore Connection?

   Under FSS Code Chapter 2, the International Shore Connection has an outside diameter of 178 mm, an inner bore diameter of 64 mm, a bolt circle diameter (PCD) of 132 mm with 4 slotted holes of 19 mm diameter, and a flange thickness of at least 14.5 mm. It must be provided with four M16 × 50 mm bolts, eight washers, and an oil-resistant rubber gasket rated for 10 bar.

2. What is the required rate of discharge for a fixed CO2 system protecting an engine room?

   For Category A machinery spaces, the fixed piping system must be capable of discharging 85% of the total statutory volume of CO2 gas into the space within 2 minutes of actuation. This rapid concentration surge is necessary to smother the fire before thermal updrafts break the gas blanket.

3. Why is CO2 prohibited as a portable extinguisher in accommodation spaces?

   CO2 is an invisible, odorless, and heavier-than-air asphyxiating gas. In small, enclosed living quarters, cabins, or alleyways, discharging a 4.5 kg CO2 extinguisher rapidly reduces the oxygen concentration below the 15% life-support threshold and creates deadly concentrations of carbon dioxide gas, causing immediate loss of consciousness.

4. How does a local application hypermist system differ operationally from total flooding CO2?

   Hypermist discharges high-pressure atomised fresh water (70 bar) directly over high-risk machinery components (fuel injection pumps, purifiers, boiler fronts) without requiring machinery shutdown, ventilation damper closure, or personnel evacuation. It is safe for crew present in the engine room and can be activated immediately upon detection of flame or smoke.