4.5 Applying Extinguishing Agents to Oil, Electrical, Gas and Enclosed-Space Fires
Key Takeaways
- Never extinguish a burning gas jet before the supply can be isolated: killing the flame while gas keeps flowing builds an unignited vapour cloud that will find an ignition source and explode.
- Foam is applied indirectly — banked off a bulkhead, rained down from above, or rolled gently onto the far edge of the pool — never plunged into the burning liquid.
- Dry powder knocks down a hydrocarbon flame in seconds but provides no cooling and leaves no vapour seal, so a foam blanket must follow immediately or the fuel will reignite off hot steel.
- Water on an energised electrical fire is prohibited: de-energise first, then treat the residual fire according to the underlying fuel using CO2 or a clean agent.
- Entering a compartment filled with high-expansion foam is done on a lifeline, because the foam removes all vision and all sound cues while leaving the atmosphere breathable but disorienting.
4.5 Applying Extinguishing Agents to Oil, Electrical, Gas and Enclosed-Space Fires
Core Principle: Column 3 of Table A-VI/1-2 lists ten practical demonstrations, and most of them are about delivery technique, not equipment selection. Choosing the right agent and then applying it badly is one of the most common ways a shipboard fire escapes.
1. Burning Liquid: Oil, Diesel and Lubricating Oil Pool Fires
The Three Legitimate Foam Application Methods
| Method | Technique | When |
|---|---|---|
| Bank-off (deflection) | Direct the stream at a vertical bulkhead, coaming or backboard just above the pool; foam loses velocity and flows down onto the surface | The standard method when a vertical surface is available |
| Rain-down | Aim high so the foam falls onto the pool under gravity, like rain | Open deck, no vertical surface, wind astern |
| Roll-on | Direct the foam onto the deck at the near edge of the pool and let it roll across the surface | Spill fires on a flat deck |
Never plunge the stream into the burning liquid. The kinetic energy breaks the fuel surface, throws flaming liquid outward, mixes fuel into the foam and destroys the blanket you are trying to build.
Foam Discipline
- Keep the blanket intact. Once you have a seal, do not walk hose or tools through it, and do not sweep it with a water jet.
- Hot steel breaks foam down. After knockdown, keep applying at a reduced rate to maintain the blanket while the metal cools, and cool the surrounding structure with fog.
- Polar solvents need alcohol-resistant foam. Alcohols, ketones and other water-miscible fuels strip conventional AFFF; a standard foam blanket will simply dissolve into them.
- Bunded and tray fires: approach with the wind behind you, extinguish the nearest edge and advance, keeping the escape route behind you at all times.
Dry Powder on Hydrocarbon Fires
Dry powder interrupts the chemical chain reaction and can knock a large hydrocarbon flame down in seconds. Its limitation defines its tactic:
Powder gives no cooling and no vapour seal. If the fuel is still above its flash point and hot steel is nearby, it will reignite as soon as the powder cloud disperses. Powder is a knockdown tool; a foam blanket must follow immediately to secure the surface.
Use the fog applicator or spray nozzle to protect the operator's approach and to cool structure while the powder does the knockdown.
2. Energised Electrical Equipment
1. DE-ENERGISE -> Open the breaker; isolate; if possible, LOTO the circuit
2. IDENTIFY -> What is actually burning now? Cable insulation? Oil? Paper?
3. ATTACK -> CO2 or clean agent while energised or uncertain;
once genuinely dead, treat as the underlying Class A or B fire
4. COOL & WATCH -> Switchboards retain heat and re-ignite; post a reflash watch
- Water and foam are conductive. A solid jet on an energised 440 V switchboard offers a path back to the operator, and seawater is a far better conductor than fresh water.
- CO₂ is the shipboard default for control stations, switchboards and electronics: non-conductive, no residue. Remember it displaces oxygen — evacuate the space after discharge.
- Avoid ABC powder on electronics. It is non-conductive and will put the fire out, but monoammonium phosphate residue combines with humidity to form phosphoric acid and destroys circuit boards and relay contacts (Section 4.1).
- Arc-flash risk. Do not open a switchboard door to "see where the fire is". Discharge through the ventilation louvres or use the fixed system.
3. Pressurised Gas Fires — The Rule That Reverses Everything
This is the single most counter-intuitive item in the syllabus and it is examined constantly.
Do not extinguish a burning gas jet unless you can immediately stop the flow of gas.
A burning jet of propane, butane, acetylene or LNG vapour is consuming its own fuel at the nozzle. Put the flame out while gas continues to escape and you convert a visible, controllable, localised fire into an invisible, expanding, unignited vapour cloud that will drift to the nearest hot surface, spark or running motor and deflagrate — often with far greater damage and casualties than the jet fire itself.
Correct Sequence for a Gas Fire
- Isolate the supply: shut the cylinder valve, the manifold valve, or the remote emergency shut-off. This alone extinguishes the fire.
- If the valve cannot be reached, cool the cylinder and surrounding structure with water spray from the maximum practical distance and from behind cover. A heated LPG cylinder can BLEVE — a boiling liquid expanding vapour explosion.
- Use a wide-angle water fog as a heat shield to advance to a valve if that approach is unavoidable, with a second charged line covering the team.
- Only extinguish the flame if isolation has already been achieved, or if the flame is preventing a rescue and the escaping gas will disperse safely.
- Evacuate downwind areas and eliminate ignition sources before, not after.
4. High-Expansion Foam Compartments
Column 3 of Table A-VI/1-2 requires a candidate to enter and pass through, with lifeline but without breathing apparatus, a compartment into which high-expansion foam has been injected. It sounds odd until you have done it.
- High-expansion foam at 500:1 to 1000:1 fills a machinery space from bilge to deckhead in minutes and smothers the fire by exclusion of air.
- The foam itself is mostly air, so the atmosphere within it is generally breathable — which is why the assessment is done without breathing apparatus.
- What it removes is every sensory reference: no vision at all, muffled sound, no sense of direction, and the sensation of being submerged. Disorientation and claustrophobic panic are the real hazards.
- The lifeline is the whole technique. Keep one hand on the line at all times, move deliberately, use the standard line signals (Section 4.3), and let the tender pay out and take up.
- Never enter a foam-filled space where fire may still be burning beneath the blanket, or where the space may also contain toxic products from the original fire, without SCBA. The unencumbered exercise is a controlled training evolution, not a tactic for a live fire.
5. Accommodation and Engine-Room Fires with Heavy Smoke
The practical demonstrations also require extinguishing a fire with water fog or any other suitable agent in an accommodation room or simulated engine room with fire and heavy smoke, and effecting a rescue in a smoke-filled space.
- Direct attack — straight stream or narrow fog onto the burning material — is used when the seat of the fire is visible and reachable.
- Indirect attack — a short burst of fog into the hot upper layer of a closed compartment from the doorway, then close the door — converts water to steam that fills the space and smothers. It is highly effective but must not be used with people inside: the steam will scald them.
- Three-dimensional gas cooling (penciling) is the routine method for advancing safely (Section 4.4).
- Match the pattern to the job: narrow fog for penetration and gas cooling, wide fog as a heat shield for advancing or protecting a rescue, straight stream for reach and for cooling hot bulkheads at distance.
Reflash watch. Every one of these fires — oil, electrical, gas, foam-smothered, or steam-extinguished — can reignite from retained heat. Nobody stands down until a dedicated watch with a charged line has monitored the compartment and a thermal imaging camera, if fitted, shows the structure cooling.
A propane cylinder in the galley store has a leaking valve and the escaping gas is burning as a steady jet. What is the correct action?
Dry powder has been used to knock down a large diesel spill fire in the engine room bilge. Why must a foam blanket be applied immediately afterwards?
What is the correct technique for applying AFFF foam to a burning pool of lubricating oil in a machinery space?
Why is the STCW practical demonstration of passing through a high-expansion foam-filled compartment performed with a lifeline but without breathing apparatus?