Fire Prevention and Basic Firefighting Principles

Fire Prevention and Basic Firefighting Principles

Fire is the most serious hazard aboard any vessel. A ship at sea has limited firefighting resources, no outside fire department, and nowhere to evacuate except the water. Every crew member must understand how fires start, how to classify them, and how to attack them correctly before a small ignition becomes a catastrophe.

How Fire Works: Triangle and Tetrahedron

The fire triangle describes the three things a fire needs to exist: fuel, oxygen, and heat. Remove any one side and the fire goes out. Modern fire science adds a fourth element — the uninhibited chemical chain reaction that sustains combustion — forming the fire tetrahedron. Some extinguishing agents (dry chemical, CO2) interrupt that chain reaction directly rather than simply cooling or smothering the flame. Understanding this explains why matching the agent to the fuel type matters so much.

Fire Classification by Fuel Type

The maritime industry uses the same letter-class system as NFPA and SOLAS:

• Class A — ordinary combustibles: wood, rope, paper, bedding, paint. Found throughout accommodations and cargo spaces.
• Class B — flammable and combustible liquids and gases: diesel, fuel oil, gasoline, LNG, paint solvents. Found in engine rooms, fuel bunkers, and paint lockers.
• Class C — energized electrical equipment: switchboards, motors, electrical panels. Found in engine control rooms and throughout the vessel.
• Class D — combustible metals: magnesium, titanium alloys. Rare on most merchant vessels but possible in specialized cargo.
• Class K — cooking oils and fats. Found in galley fryers and ranges.

A shipboard fire may involve more than one class at the same time. A diesel fire (Class B) near live wiring is also Class C until the circuit is de-energized.

Selecting the Correct Extinguisher

Portable extinguishers carry labels showing which classes they handle. Using the wrong agent can make a fire worse or create a new hazard.

| Extinguisher Type | Effective On | Avoid On | Why |

|---|---|---|---|

| CO2 | B, C | A (limited) | Displaces oxygen; leaves no residue; safe on electronics |

| ABC Dry Chemical | A, B, C | K, D (specialist) | Interrupts chain reaction; residue can damage electronics |

| AFFF Foam | A, B | C (electrical) | Forms vapor-suppressing blanket on liquids; conducts electricity |

| Class K Wet Chemical | K | — | Saponifies cooking oil; knocks down flame and prevents re-ignition |

| Water / Water Mist | A | B, C (plain water) | Cools Class A; water mist units rated C use fine droplets that do not conduct |

For most engine-room liquid fuel fires, AFFF or dry chemical is the first portable choice. For electrical panels, CO2 is preferred because it leaves no conductive residue and does not damage equipment further.

The PASS Technique

Every portable extinguisher is operated the same way regardless of agent type:

1. P — Pull the safety pin. Break the tamper seal. This unlocks the handle.

2. A — Aim the nozzle or horn at the base of the fire, not at the flames. Hitting the base attacks the fuel-air interface where combustion occurs.

3. S — Squeeze the handle firmly and steadily.

4. S — Sweep side to side across the base of the fire until the flames are out or the extinguisher is empty.

Always keep your back to an exit route. If the fire is not knocked down within the first few seconds of discharge, back away, sound the alarm if not already done, and do not re-engage without additional resources.

Pre-Use Extinguisher Inspection

Before any deployment — and as part of routine monthly checks — inspect each extinguisher:

• Pressure gauge needle must be in the green zone. A needle in the red (low or overcharged) means the unit is unserviceable.
• Safety pin must be present and intact.
• Tamper seal (plastic tag or wire) must be unbroken, confirming the unit has not been partially discharged.
• Nozzle and hose must be clear of blockage.
• Label must be legible and show the current inspection date.

NFPA 10 governs inspection, testing, and maintenance standards for portable fire extinguishers in the United States.

Fixed Suppression Systems and When NOT to Fight

Ships also carry fixed systems — CO2 total-flooding systems in machinery spaces and paint lockers, and water-based sprinkler or deluge systems in accommodation areas. Before a fixed CO2 system discharges, an alarm sounds and a time delay begins to allow personnel to evacuate. Never re-enter a space after CO2 release without a self-contained breathing apparatus (SCBA). CO2 is colorless, odorless, and lethal at firefighting concentrations.

Fire dampers automatically close to isolate ventilation ducts and starve the fire of air. Emergency stops shut off fuel supply pumps and ventilation fans. Know the location of these controls on your vessel's fire control plan — a SOLAS-required diagram posted at the gangway and on the bridge.

PPE and Safety Rules for Live Fire Training

• Wear gloves and face shield during any extinguisher discharge.
• Never stand downwind of a CO2 horn; the expanding gas chills to approximately −78 °C and can cause frostbite on bare skin.
• Dry chemical residue irritates the eyes and lungs; wear safety glasses and avoid breathing the cloud.
• During training evolutions, one instructor acts as safety officer with an additional charged extinguisher standing by at all times.
• After any discharge, treat the extinguisher as empty and tag it out of service for recharge before it is returned to its mount.