Shipboard Firefighting and Damage Control: Picking the Agent, Fighting the Space

What the rule requires

Three legs, and four ways to break them

A fire needs a combustible material, a sufficiently high temperature, and a supply of oxygen — heat, fuel, oxygen, the fire triangle NAVEDTRA 14057 Ch. 4 — Fire Components. Remove any one side and the fire goes out.

The fourth avenue is not a leg of the triangle at all: a fire may also be extinguished by slowing the rate of combustion NAVEDTRA 14057 Ch. 4 — Fire Extinguishment. That is what dry chemical does. Purple-K-Powder interrupts the chemical reaction by suspending fine particles in the fire, screening heat from oxygen and fuel just long enough for the fire to go out NAVEDTRA 14057 Ch. 4 — Review Answers.

Removing the heat side means cooling the fuel below the temperature at which it will support combustion, and water is the most commonly used cooling agent — solid stream, fog, or in combination with AFFF NAVEDTRA 14057 Ch. 4 — Removing Heat. Heat reaches the next compartment by radiation, conduction and convection. Convection is the one that catches engineers out: a ventilation system can carry heated gases several compartments away and start a fresh fire in any space served by that system where combustibles of low flash point are stowed.

Classes, and the agent that suits each

Fires are classified by the nature of the fuel, and that classification determines how the fire must be extinguished NAVEDTRA 14057 Ch. 4 — Fire Classifications. The mnemonic in general circulation is Ash, Barrels, Current, Metals, Kitchen — sound, provided you read D as combustible metals rather than the "dust" some versions use, and K as cooking oils specifically USCG Boatswain Manual Ch. 6 §6.1.

ALPHA — ordinary combustibles: wood, cloth, paper, upholstery. Extinguished with water, high or low velocity fog or solid streams. ALPHA fires leave embers or ashes and must always be overhauled.
BRAVO — the vapour-air mixture over the surface of flammable liquids: gasoline, diesel oil, fuel oil, paints, thinners, solvents, lubricating oils, greases. AFFF, Halon 1211, Halon 1301 or dry chemical PKP; which one depends on the circumstances of the fire.
CHARLIE — energised electrical equipment. Nonconducting agents only: PKP, carbon dioxide, Halon 1211. CO2 and Halon 1211 are preferred because they leave no residue.
DELTA — combustible metals such as magnesium, titanium and sodium. Jettison the burning material overboard if you can; otherwise cool it below its ignition temperature with large amounts of water. A magnesium fire can be smothered with a large volume of dry sand.
KILO — cooking oils, the galley fire. Aboard ship the fixed protection for deep-fat and doughnut fryers and their exhaust systems is the aqueous potassium carbonate (APC) system, its cylinders pressurised with nitrogen NAVEDTRA 14057 Ch. 6 — Review Answers.

An energised main switchboard is burning. You have PKP, CO2 and a charged 1 1/2-inch hose at hand. Which do you use, and why not the others?

CO2. The fire is CHARLIE, so the agent must be nonconducting, which rules out the hose. PKP is nonconducting and permitted, but CO2 leaves no residue and is preferred for that reason — PKP is known to foul electrical and electronic components as well as the internal parts of turbines and engines.

AFFF: three jobs in one agent

AFFF is primarily used aboard ship against class BRAVO fires, often in conjunction with PKP NAVEDTRA 14057 Ch. 6 — System. It is effective against those fires because it does three separate things: as foam it floats on top of the flammable liquid and prevents vapours being released to the atmosphere; it prevents oxygen reaching the liquid; and being a mixture of concentrate and water, it cools NAVEDTRA 14057 Ch. 7 — Attacking a Fire. Covering hot spots with AFFF is therefore highly effective against reflash. It will also vapour-seal a small fuel spill NAVEDTRA 14057 Ch. 5 — Review Answers.

Portable delivery is through an in-line eductor, which mixes seawater and AFFF concentrate to produce the solution. An eductor is a jet-type pump with no moving parts.

Fixed systems in a machinery space

CO2 and Halon 1301 both flood a space, and the exam separates them on when each is used and what each demands of you before release.

The CO2 flooding system should only be used in spaces that are normally not occupied by personnel, and before operating an installed CO2 system you ensure all openings in the compartment are closed and the ventilation system for the space is secured . Working the CO2 hose-and-reel, direct the discharge toward the base of the fire. With a portable CO2 extinguisher, ground the cylinder to the deck before use .

Halon 1301 is installed in fixed flooding systems for extinguishing flammable liquid fires and is the more commonly used of the two Halons aboard NAVEDTRA 14057 Ch. 6 — Halon Systems. Both Halons chemically inhibit the flame front. Halon decomposes on contact with flames or hot surfaces above 900°F (482°C), and the decomposition products are principally hydrogen fluoride and hydrogen bromide, which have a sharp irritating odour even at low concentrations. Full discharge into the protected space is completed in 10 seconds, and that short discharge time keeps the thermal decomposition products well below lethal concentrations . Halon systems are used for fires beyond the capacity of fire extinguishing equipment and where abandonment of the space is necessary; in machinery spaces and pump rooms an AFFF sprinkling system normally supplements Halon 1301.

Halon 1211, by contrast, is not used in total flooding systems. It is sprayed as a liquid, and is fielded as portable 20-pound extinguishers and in twin-agent AFFF/Halon 1211 apparatus .

Boundaries

Fire boundarymen proceed directly to the scene when a fire is called away and set primary and secondary boundaries as directed by the repair party leader or fire marshal, securing all doors, hatches and openings in the boundary of the fire area and removing or relocating combustibles NAVEDTRA 14057 Ch. 2 — Function ¶2.

Primary fire and smoke boundaries are set at all bulkheads immediately adjacent to the fire, manned with a fire hose to cool the bulkhead. The secondary set goes at the next immediate watertight bulkhead from the scene. If a boundary fails and the fire cannot be contained, the boundaryman secures the space and evacuates, and what were secondary boundaries become the primary NAVEDTRA 14057 Ch. 7 — Type of Attack ¶1. Fire spreads through any penetration: ventilation, electrical cableways, piping conduits, or defective welds under extreme heat. The boundaryman watches his bulkhead or deck for smouldering or blistering paint and for smoke through penetrations. DCC and all repair lockers plot the boundary information.

For a class BRAVO fire in a machinery space, the area between the inner and outer smoke boundaries is the buffer zone NAVEDTRA 14057 Ch. 13 — Aqueous Film-Forming Foam Fire ¶2. In flooding, the boundaries are the first set of watertight transverse bulkheads forward and aft of the flooded compartment .

Firemain and the hose station

The firemain supplies seawater primarily to the fireplug and sprinkling systems . The plugman connects the hose to the fireplug and, when directed and with the nozzle closed, opens the fireplug valve to activate the hose . He then watches for loss of pressure or rupture. On loss of water pressure, report to the on-scene leader and secure the plug. On a ruptured hose, secure the fireplug, replace the ruptured section, and reactivate the hose as quickly as possible.

A firemain rupture may be jumpered around, and a P-100 pump may replace a fire pump if the ship's electrical system takes a casualty NAVEDTRA 14057 Ch. 7 — Fire-Fighting Strategies. The P-100 produces carbon monoxide when operated .

Protection built into the vessel

Accommodation spaces are separated from machinery and fuel tank spaces by a fire resistant boundary that prevents the passage of vapours, and every pipe and cable penetration through that boundary must be sealed 46 CFR §28.380. Paint and flammable liquids go in a steel or steel-lined locker. Where insulation is used in a space holding flammable liquids or vapours — machinery spaces, paint lockers — it must be covered by a vapour barrier 46 CFR §177.405. Engine exhausts and galley uptakes are kept clear of and insulated from combustible material.

Telling it apart

The three ignition temperatures

One criterion separates them: what has to be present for the vapours to burn.

Flash point — the lowest temperature at which a flammable substance gives off vapours that will burn when a flame or spark is applied NAVEDTRA 14057 Ch. 4 — Fire Components.
Fire point — the temperature at which the fuel will continue to burn after ignition. Usually a few degrees above the flash point.
Auto-ignition (self-ignition) point — the lowest temperature to which a substance must be heated to give off vapours that burn without a spark or flame. This is the figure that governs re-entry into a hot space.

What each agent leaves behind

Water — cools; the sea is an inexhaustible supply NAVEDTRA 14057 Ch. 4 — Review Answers. Conducts, so not on energised gear.
AFFF — smothers, vapour-seals and cools. Can be used alone or with PKP.
PKP — interrupts the chemical reaction. Nonconducting, but fouls electrical and electronic components and the internal parts of turbines and engines NAVEDTRA 14057 Ch. 5 — Review Answers.
CO2 — smothers; colourless, odourless, no residue NAVEDTRA 14057 Ch. 13 — Aqueous Film-Forming Foam Fire ¶2.
Halon 1301 — dense, colourless, odourless, does not conduct electricity, leaves no residue . Decomposes above 900°F into hydrogen fluoride and hydrogen bromide.

Working a question

A fuel oil spray fire in the main machinery space. Watchstanders have evacuated and Halon has been activated. Sequence the required actions.

Classify the fire. Fuel oil burning in the vapour-air mixture over the liquid surface is BRAVO, which puts AFFF, PKP and Halon in play and rules out a plain water attack as the primary agent NAVEDTRA 14057 Ch. 4 — Fire Classifications.
Account for personnel. Evacuees muster outside the designated smoke and fire boundaries; missing personnel are reported to DCC. Evacuating watchstanders report whether bilge sprinkling was used, whether the source of the fire was secured, and whether Halon was activated, with the time of activation NAVEDTRA 14057 Ch. 7 — Type of Attack ¶1.
Isolate. The repair party electrician secures electrical power to all affected compartments and reports it to the on-scene leader NAVEDTRA 14057 Ch. 2 — Function ¶2. Electrical isolation must be complete before re-entry, lighting excepted, and that decision rests with the on-scene leader; mechanical isolation need not be complete, though it makes the space safer NAVEDTRA 14057 Ch. 7 — Preparing to Enter the Space ¶1.
Set boundaries before the space is opened. Proper fire boundaries must be set prior to accessing the compartment so that the attack team has a safe area to work from.
Determine whether Halon worked. Investigators observe smoke colour through the battle ports at the escape trunk and report to DCC NAVEDTRA 14057 Ch. 7 — Type of Attack ¶2. Effective: allow at least 15 minutes before entry. Not effective: attempt re-entry as soon as evacuation and mechanical isolation are complete, using secondary Halon if available NAVEDTRA 14057 Ch. 7 — Preparing to Enter the Space ¶2.
Activate AFFF bilge sprinkling for 2 minutes prior to entry.
Attack. Direct attack is the ideal method: short bursts with a narrow fog or direct stream, advancing into the fire area and applying AFFF onto the fire NAVEDTRA 14057 Ch. 7 — Attacking a Fire. If conditions do not allow entry, an indirect attack introduces fog through a cracked doorway or any available penetration, and the team then enters and attacks directly.
Station the reflash watch once the team leader is satisfied the fire is out — near the seat of the fire with a charged hose, with a hoseman tending it.
Overhaul. The team leader and a second hose team search for hangfires with the NFTI, in chop mode, examining all cableways, areas beneath deckplates and overheads.
Ventilate and test. Oxygen must be between 19.5 and 22 percent, and because Halon 1301 was discharged, test for hydrogen fluoride NAVEDTRA 14057 Ch. 7 — Review Answers.

Where candidates lose the point

Answering "water" for a fuel oil fire because water is the agent the ship has in unlimited supply. Water is the ALPHA agent; the BRAVO list is AFFF, Halon 1211, Halon 1301 and PKP NAVEDTRA 14057 Ch. 4 — Fire Classifications.
Answering "increase air flow with blowers" or "open the ventilators" on a fixed CO2 release, on the reasoning that the agent needs to be distributed. All openings closed, ventilation secured NAVEDTRA 14057 Ch. 6 — Review Answers.
Answering "open the space and douse with water to prevent reflash" after a fixed release. Opening an access introduces fresh oxygen, and if space temperatures are above the auto-ignition point of any combustible present, it starts burning again the moment air reaches it NAVEDTRA 14057 Ch. 7 — Attacking a Fire. The space is tested, not opened and hosed.
Treating Halon 1301 as harmless because it does not conduct and leaves no residue. The decomposition products are hydrogen fluoride and hydrogen bromide, and the real hazard is the products of combustion such as carbon monoxide combined with oxygen depletion, heat and smoke NAVEDTRA 14057 Ch. 6 — Halon Systems.
Putting the primary boundary at the next watertight bulkhead. That is the secondary. Primary goes at every bulkhead immediately adjacent to the fire NAVEDTRA 14057 Ch. 7 — Type of Attack ¶1.
Calling an ALPHA fire out when the flame is out. ALPHA fires leave embers or ashes and must always be overhauled NAVEDTRA 14057 Ch. 4 — Review Answers.
Reaching for an EEBD to fight the fire. The EEBD provides a limited amount of breathable oxygen to evacuating personnel and is not used to combat a fire; it gives 10 minutes of oxygen for escape and is a one-time use device . The equipment that produces its own oxygen and allows entry into otherwise uninhabitable areas is the OBA NAVEDTRA 14057 Ch. 5 — Review Answers.

Check yourself

You are the plugman. The nozzleman is at the door of the space and the team leader orders the hose activated. What do you do, and in what order?

Confirm the nozzle is closed, then open the fireplug valve. Thereafter watch the hose for loss of water pressure or rupture: on loss of pressure, report to the on-scene leader and secure the plug; on a rupture, secure the fireplug, replace the ruptured section, and reactivate the hose as quickly as possible.

A magnesium fitting is burning on the weather deck. Which action is required first, and what is your fallback?

Jettison the burning material overboard if possible. If not, most DELTA fires are fought by applying large amounts of water to cool the material below its ignition temperature; a magnesium fire can also be smothered with a large volume of dry sand.

Halon 1301 has discharged into the machinery space and investigators report the smoke observed through the escape trunk battle ports indicates the agent was effective. How long before you enter, and what precedes entry?

At least 15 minutes. Activate AFFF bilge sprinkling for 2 minutes before entry, complete electrical isolation except for lighting, and have primary and secondary boundaries set.

Post-fire, the compartment has been ventilated. What oxygen reading permits entry without breathing apparatus, and what additional gas test does a Halon 1301 discharge require?

Between 19.5 and 22 percent oxygen. Because Halon 1301 was used, test for hydrogen fluoride — Halon decomposes above 900°F into hydrogen fluoride and hydrogen bromide.

A small diesel spill is burning in the bilge and has been knocked down. Which agent do you put on the hot fuel surface, and what three things is it doing there?

AFFF. It floats on the flammable liquid and prevents vapours being released to the atmosphere, prevents oxygen reaching the liquid, and cools because the foam is a mixture of concentrate and water. That combination is what makes covering hot spots with AFFF effective against reflash, and it will vapour-seal the remaining spill.

Your boundary bulkhead begins to show blistering paint and smoke is coming through a cable penetration. What has happened to your boundaries?

The primary boundary is failing. Secure the space and evacuate if it cannot be held; the secondary boundaries at the next watertight bulkhead then become the primary, and personnel attack the new threat. Boundary changes are plotted by DCC and all repair lockers.

The team leader reports the fire out. Who stands the reflash watch, where, and with what?

A hoseman assumes the duties of reflash watch when directed. He remains near the seat of the fire with a charged hose and observes the area to ensure no new fire breaks out, with normally at least one other hoseman on scene to tend the hose.