The Basics and Benefits of Foam Applications in Firefighting
When it comes to introducing foam agents in fire operations, department officers have a lot to consider. They must make decisions and coordinate activities related to hardware specifications, purchases, and firefighter training. The main goal of implementing a foam program is to reduce fire losses and enhance firefighter safety. A crucial step in this process is developing a comprehensive training and education plan to demystify foam usage, its mechanics, and best practices.
Principles and Practices of Foam Applications
Class A Foam
Class A foams are specifically designed for combating fires involving ordinary combustible materials, not flammable liquids. These foams are typically synthetic, detergent-based, and biodegradable, posing minimal environmental risk when used correctly.
Class A foam enhances firefighting effectiveness by reducing the surface tension of water, allowing it to penetrate deeper into cracks and crevices of the burning material, thereby improving moisture penetration and cooling. When mixed with water at low ratios (0.3% to 0.5%), Class A foam creates bubbles that can be generated using various systems such as fog nozzles, air-aspirating nozzles, high-expansion foam generators, and Compressed Air Foam Systems (CAFS).
The foam blanket produced clings to both horizontal and vertical surfaces, providing prolonged contact with the burning material, which helps to cool it and slow down the pyrolysis process.
Class B Foam
Class B foams are essential for flammable liquid fires. One popular formulation is Aqueous Film Forming Foam (AFFF), known for its excellent performance in extinguishing flammable liquid fires. AFFF forms a physical barrier over the fuel, suppressing vapors and providing effective flame knockdown. Alcohol Resistant AFFF (AR-AFFF) is necessary for polar solvent fuels like Ethanol 85 (E85) as it forms a polymeric membrane to separate the foam blanket from the fuel.
For Class B foams to be effective, they must be applied at rates greater than the breakdown rate of the foam blanket caused by the fire's heat. Manufacturers provide specific application rates, verified through third-party testing, that must be followed to ensure successful suppression.
Advanced Foam Technologies: CAFS
Compressed Air Foam Systems (CAFS) represent the latest advancement in foam generation. These systems inject high-volume compressed air into a foam solution, producing a high-quality finished foam that is more effective than traditional nozzle-aspirated foam systems. CAFS can be used with both Class A and Class B foams, making them versatile for various firefighting scenarios.
CAFS technology offers several benefits, including lightweight hose lines, rapid flame knockdown, and reduced labor during overhaul. However, they require adjustments to traditional firefighting strategies and thorough training to maximize their benefits.
Modern CAFS engines typically feature a foam concentrate proportioner and a rotary air compressor, with many systems designed to be user-friendly and automatic, reducing the operational burden during emergencies. Retrofitting existing apparatus with CAFS using air cylinders is a cost-effective alternative for departments looking to upgrade their firefighting capabilities.
Practical Applications and Considerations
Class A foam can be effectively used in various fire scenarios, including interior structure fires, vehicle fires, wildland fires, and more. Using Class A foam reduces water usage and exposure to heat and toxic fumes, enhancing firefighter safety.
In rural areas, where water supply is a challenge, Class A foam significantly reduces the amount of water needed, decreasing the risk of roadway accidents involving water tankers.
For new fire apparatus designs, incorporating both Class A and Class B foams should be a priority. CAFS technology, in particular, should be considered for its enhanced firefighting capabilities and operational efficiency.
In conclusion, the strategic use of foam agents can greatly enhance firefighting effectiveness and safety. Departments should invest in proper training, equipment, and technology to fully leverage the benefits of foam applications in fire operations.