AFFF foam is the preferred method for extinguishing Class B fires on ships

Title: When Foam Wins: Handling Class B Fires on Deck

Picture this: a slick sheen on the deck, a hiss of vapors lifting like poker-hot steam, and flames that seem to dance right above the liquid fuel. Class B fires—flammable liquids such as gasoline, oil, diesel, and other hydrocarbons—move fast. They don’t just burn; they spread, vaporize, and can flare up with little warning. In sea service, the right tactic isn’t just about barking orders; it’s about choosing a strategy that actually cuts off the fuel’s life line. And for many situations, that strategy is AFFF foam.

Understanding the enemy: what makes Class B fires tick

Class B fires aren’t solved by splashy water alone. Water can spread a burning liquid, pushing fuel to new pools where more flames spring up. Even if you cool the surface, you might leave pockets of fuel somewhere else that can reignite later. The key is to address both the liquid fuel and its vapors. Vapors can burn ahead of the visible flame, and the surface of a slick fuel can keep re-igniting as long as fuel remains.

Think of it like throwing a blanket over a hot, spreading surface. If you can smother the flames while keeping the fuel from venting vapors, the fire loses its grip. That’s precisely what the foam does.

A look at the main options, and why some are better than others

Here’s how the common choices stack up, in plain talk:

• Water directly on the liquid fire (A): This is usually a bad idea for Class B fires. Water and oil don’t mix; the water tends to break the surface tension and push fuel to other areas. In short, it can spread the blaze rather than quench it.

• AFFF or foam (B): This is the star option. AFFF—Aqueous Film-Forming Foam—forms a thin, adhesive film on the fuel surface. It’s brilliant at two things: vapor suppression and smothering the flames by creating a barrier between fuel and air. It also blankets the liquid, cooling the surface beneath. Foam gives you a longer window to control and cool the fire, reducing the chance of re-ignition.

• Dry chemical agents (C): Dry chem shows up in many fleets as a quick knockdown option. It disrupts the chemical reactions happening at the flame. But it doesn’t form the same continuous, lasting barrier that foam does. Once the dry chemical settles and dissipates, fuel surfaces can rekindle if fuel remains.

• CO2 (D): Carbon dioxide displaces oxygen and can smother small fires. For larger Class B fires, CO2 loses its edge. It cools the space only to a limited extent and doesn’t address the slick on the surface. In big spills, the fuel keeps feeding the flame.

Why foam tends to win in many real-world scenarios

Consider the job foam does with a fuel spill on a deck or in a compartment. When foam hits the surface of the liquid, it spreads rapidly, creating that film layer. That film does a couple of essential things at once:

• Vapors go quiet. The foam forms a barrier that traps and cools the vapors rising from the fuel. Less vapor means less chance the fire rips back to life in a flare.

• The liquid is smothered. The foam blankets the surface, smothering the flames by cutting off the oxygen that fuels combustion at the liquid’s surface.

• The surface cools down. Foam contains a cooling effect—water still plays a role, but the foam keeps a larger fraction of the cooling inside the blanket, which slows heat transfer to the fuel.

• Re-ignition risk drops. With the fuel covered and the surface cooled, pockets of fuel lose their ignition sources, and the fire becomes easier to control.

Foam in action: practical moments on a ship or in a port setting

Real life aboard a vessel isn’t a textbook scene; it’s a moving, weather-affected problem. Here are some relatable situations where foam shines:

• Engine room spill: A spill from a fuel line or a leaking tank creates a slick that can creep toward hot surfaces or electrical equipment. Foam creates a protective shield over that slick, buys time to shut valves, and reduces the chance of a flash when a hot surface finds fuel.

• Cargo deck spill: A fueling operation, a misstep during bunkering, or a leak from a container can leave a glowing pool on the deck. Foam blankets the pool, suppressing vapors and preventing airborne ignition. Then, while the crew secures the source, responders can manage ventilation and eliminate ignition sources.

• Small openings, big consequences: Even a small, undetected fuel film can flash if exposed to an ignition source. Foam helps cover those hidden patches, so responders aren’t chasing flames around fuel residues.

How to think about deployment and technique (without getting lost in nitty-gritty)

If you’re part of the crew facing a Class B situation, keep these guiding ideas in mind:

• Start with coverage, not rush. AFFF foam needs to blanket the liquid. Move the nozzle steadily, ensuring the foam forms a continuous layer over the spill.

• Don’t forget the surface beneath. The aim isn’t just to splash the surface—it's to create a stable film that won’t shear off as the fire shifts or as the ship moves.

• Coordinate with cooling. While foam handles the surface, you’ll still want to cool nearby hot zones and prevent heat from driving more fuel into the fire. A combined approach works best.

• Watch for hidden fuel. Foam is excellent on the surface, but if fuel has leaked into bilges, voids, or bilge wells, you’ll need separate strategies to address those pockets, including sealing, ventilation, or targeted suppression.

• Keep people safe. A Class B fire can produce dense vapors and sudden flare-ups. Protective gear, communication, and clear escape routes matter as much as the foam itself.

What about other strategies? When foam isn’t the whole story

There are times when foam is just part of a larger toolbox:

• Dry chemical or CO2 might be used for smaller, controlled fires or for initial knockdown while foam is being prepared. They can help reduce flame intensity quickly, giving foam crews a chance to lay down the thicker blanket.

• Ventilation and fuel source isolation are critical. Cutting off fresh air and stopping the fuel supply is often the real game-changer, letting the foam do the heavy lifting.

• Post-fire management matters too. Even after flames die down, lingering vapors and residual fuel can reignite if the surface isn’t thoroughly cooled and kept covered. A without-foam plan is incomplete here.

A few practical tips that stick with crews

• Practice with your foam system so you’re not hunting for controls in the heat of an incident. Familiarity makes all the difference when timing matters.

• Keep the foam concentrate within easy reach and verify the mix ratios. AFFF needs the right balance to form that protective film.

• Maintain a constant watch. The blanket can fail if the surface shifts or if new fuel sources appear. Vigilance is part of the plan.

• Remember that clean-up matters. Once the blaze is out, you’ll still have fuel residues and possible re-ignition pockets. Proper drainage, containment, and checks prevent a later flare.

A quick mental checklist for Class B scenarios

• Assess the spill: size, location, and potential ignition sources.

• Decide on a foam-first approach when feasible.

• Apply foam to cover the surface and form a vapor-suppressing blanket.

• Use additional cooling and fuel-source control as needed.

• Monitor the area for re-ignition risks and lingering vapors.

A closing thought: resilience through smart choices

Class B fires test the seamanship of a crew as much as their equipment. It’s tempting to lean on whatever feels fastest, but the long game—safety, control, and preventing a recurrence—rests on choosing strategies that actually curb fuel and vapor dynamics. Foam isn’t magical, but it’s a proactive tool that aligns with how hydrocarbons behave on water and steel. When used correctly, it buys time, reduces danger, and keeps the deck safer for the crew and the ship alike.

If you’re ever asked to weigh these options in a real-world scenario, remember this: water alone can spread a Class B fire; dry chemicals interrupt combustion but don’t seal the surface; CO2 can help small fires but falls short for larger spills. AFFF or foam, by forming a protective film and suppressing vapors, often provides the most reliable path to control. The goal isn’t just to put the flames out; it’s to keep the flames from coming back and to give the crew room to work safely.

In the end, the best firefighting plan is the one that blends solid technique with calm judgment. Foam gives you that steady edge when the liquid fire underwrites the drama. And on a ship, where every second counts and every decision matters, that edge is priceless.