Firefighting foam plays a crucial role in modern fire suppression, particularly in situations where water alone is ineffective or even dangerous. Firefighting foam is a specially formulated solution designed to suppress fires by creating a barrier between the fuel and the oxygen it needs to burn. It is especially valuable in combating fires involving flammable liquids, such as gasoline, diesel, jet fuel, and other hydrocarbons. This article explores the composition of firefighting foam, how it works, the different types used, and the scenarios in which it is most effective.
Understanding Firefighting Foam
Firefighting foam is a stable mass of small, air-filled bubbles with a lower density than most flammable liquids. It is composed of 3 primary components: Water, foam concentrate (a chemical agent), and air. The concentrate is mixed with water to create a foam solution, which is then aerated (usually via a nozzle or foam generator) to create foam.
The foam acts as a blanket, smothering the fire and forming a barrier between the fuel surface and the air. It also cools the fuel and surrounding surfaces, preventing re-ignition. This dual-action—separation and cooling—makes foam extremely effective in many fire scenarios.
The Purpose and Benefits of Firefighting Foam
Firefighting foam is used when water alone is not sufficient to extinguish a fire, particularly in Class B fires (those involving flammable liquids and gases). Water can spread the burning liquid, making the fire worse. Foam, on the other hand:
- Suppresses Vapors – By forming a film or blanket over the fuel, foam prevents flammable vapors from escaping and mixing with oxygen.
- Excludes Oxygen – Foam blankets the fire, cutting off the oxygen supply and stopping combustion.
- Cools the Fuel – Water in the foam absorbs heat, reducing the temperature of the fuel and its surroundings.
- Prevents Reignition – The insulating layer formed by foam remains in place after the fire is out, reducing the risk of flare-ups.
Types of Firefighting Foam
There are several types of firefighting foam, each designed for specific applications and types of fires:
1. Aqueous Film Forming Foam (AFFF)
AFFF is one of the most commonly used foams for Class B fires involving hydrocarbon fuels like gasoline or diesel. It forms an aqueous film that spreads across the fuel surface, cutting off the oxygen supply. AFFF is known for its fast knockdown capabilities and is widely used in airport fire services, military applications, and industrial facilities.
2. Alcohol-Resistant AFFF (AR-AFFF)
This variant of AFFF is designed to handle polar solvent fires (such as alcohols, ketones, and esters) that can break down regular foam. AR-AFFF creates a polymeric layer between the foam and the fuel, protecting the foam from degradation and maintaining its effectiveness.
3. Class A Foam
Used for fires involving ordinary combustibles like wood, paper, and vegetation (Class A fires), this foam is primarily a wetting agent. It reduces the surface tension of water, allowing it to penetrate deep into burning materials. This is especially helpful in wildland firefighting and structural fire suppression.
4. High Expansion Foam
This foam has a much higher air-to-liquid ratio, producing a large volume of foam from a small amount of solution. It is used in enclosed spaces such as aircraft hangars, ship holds, and basements. High expansion foam fills the area, displacing air and suffocating the fire.
5. Protein and Fluoroprotein Foams
These older foams are derived from natural proteins and have excellent heat resistance. While not as commonly used today as AFFF, they are still found in some industrial applications, particularly where slow drainage and long-lasting foam blankets are desired.
Applications of Firefighting Foam
Firefighting foam is used in a variety of scenarios across different sectors:
1. Industrial and Petrochemical Facilities
These sites often handle flammable liquids in bulk. Storage tanks, pipelines, and loading racks are all potential ignition points. Foam systems are installed for fire protection and mitigation in case of spills or tank fires.
2. Airports and Aircraft Fires
Aircraft carry large volumes of jet fuel, which can ignite in accidents or crashes. AFFF and AR-AFFF are standard at airports for rapid fire suppression. Foam can extinguish fire and prevent fuel from igniting further.
3. Wildland and Forest Fires
While foam is less common here than water or fire retardants, Class A foam can be used to increase the effectiveness of water. It allows deeper penetration into vegetation and wood, making it useful in mop-up operations and structural protection in the wildland-urban interface.
4. Marine and Shipboard Fires
Foam is critical aboard ships, where flammable liquids and enclosed spaces create high fire risks. High expansion foams can quickly flood cargo holds or engine rooms, suppressing fires that are hard to reach.
5. Military Operations
Due to the presence of fuel depots, aircraft, and vehicles, the military extensively uses firefighting foam, particularly AFFF, for rapid response to fuel fires.
Environmental and Safety Concerns
While effective, some firefighting foams—especially those containing per- and polyfluoroalkyl substances (PFAS)—have raised environmental and health concerns. PFAS compounds are persistent in the environment and have been linked to health risks.
As a result, many organizations and governments are phasing out PFAS-containing foams and investing in fluorine-free alternatives. These new foams are designed to maintain high performance while reducing environmental impact.
Firefighters must also handle foam concentrates with care. Appropriate personal protective equipment (PPE) should be used during application, and proper containment and cleanup procedures must be followed to minimize environmental release.
Foam Application Techniques
Foam can be applied in different ways, depending on the situation:
- Aspirated Foam Nozzles: These mix air into the solution to produce high-quality foam with a long throw range.
- Compressed Air Foam Systems (CAFS): Mix water, foam concentrate, and compressed air to produce a fine, consistent foam ideal for structural and wildland fires.
- Fixed Foam Systems: Installed in high-risk areas such as fuel storage tanks, they automatically discharge foam in the event of fire.
- Mobile Foam Units: Found on fire trucks or trailers, they allow foam to be applied in flexible and variable volumes during an emergency.
Conclusion
Firefighting foam is a vital tool in the fire service arsenal, particularly for fires involving flammable liquids or large-scale industrial risks. By smothering flames, suppressing vapors, and cooling hot surfaces, foam enhances firefighting effectiveness in ways water alone cannot. While traditional foams like AFFF have proven indispensable, the industry is now evolving toward safer, environmentally friendly alternatives.
Understanding how and when to use firefighting foam is essential for modern emergency responders, industrial safety teams, and facility managers. As technology and environmental standards continue to evolve, so too will the development of foam agents, ensuring that fire suppression remains both effective and responsible.
