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Firefighting foams have long been used as one of the most reliable suppression agents for liquid fuel fires and other high-risk scenarios. Over the years, conventional foam systems have evolved into more advanced technologies, including Compressed Air Foam Systems (CAFS), which offer enhanced fire control capabilities. Understanding the differences between these two approaches is critical for selecting the right fire protection strategy.
Normal firefighting foam is produced by mixing foam concentrate with water and air (atmospheric aspiration) through a foam-making branch pipe, nozzle, or generator. The expansion ratio may be low, medium, or high depending on the application.
Common types: Aqueous Film Forming Foam (AFFF), Alcohol-Resistant AFFF (AR-AFFF), Fluorine-free foams.
Applications: Hydrocarbon fires, flammable liquid storage, chemical plants, tank farms, aircraft hangars, and industrial facilities.
Compressed Air Foam is a specialized foam system where air is mechanically injected under pressure into the water-foam concentrate mixture, creating a denser, smaller-bubble foam with superior adhesion and cooling properties.
Unlike conventional aspirating nozzles, CAFS produces foam inside the system itself, ensuring a consistent, stable bubble structure.
Produced by: Mixing foam concentrate, water, and compressed air in a controlled ratio.
Foam Quality: Thick, homogeneous, clingy foam blanket with slower drainage.
Several international standards recognize and cover CAFS:
NFPA 11 – Standard for Low-, Medium-, and High-Expansion Foam (references CAFS for foam generation and application).
NFPA 1150 – Standard on Foam Chemicals for Fires in Class A Fuels.
NFPA 1901 – Standard for Automotive Fire Apparatus (includes requirements for CAFS-equipped fire engines).
UL 162 – Foam Equipment and Liquid Concentrates (lists performance of foam equipment including CAFS).
These standards provide guidance on design, installation, testing, and maintenance of compressed air foam systems.
Normal Foam:
Effective for large-scale hydrocarbon pool fires and fixed-system applications (e.g., storage tanks, bunds).
Works well where large foam volume is needed quickly.
Compressed Air Foam:
More effective for Class A fires (wood, paper, plastics) and wildland fires due to superior cooling and penetration.
In structural firefighting, CAFS has been proven to use less water, provide better knockdown, and reduce rekindle risk.
For hydrocarbon pool fires, CAFS may be effective but normal foam systems are generally preferred for very large fuel-surface coverage.
In summary: CAFS is more efficient in terms of water usage and firefighting performance for Class A and confined fires, while normal foam systems remain dominant for large-scale hydrocarbon hazards.
✅ Improved fire suppression – better wetting, cooling, and penetration.
✅ Water efficiency – less water consumption reduces water damage and runoff.
✅ Adhesion – foam clings to vertical and irregular surfaces.
✅ Reduced weight – hoses charged with CAF are lighter and easier to handle.
✅ Longer drain time – foam blanket lasts longer, reducing reignition risk.
✅ Versatility – effective for Class A fires, structural, wildland, and vehicle fires.
⚠️ Not ideal for large hydrocarbon storage fires where large volumes of foam are required.
⚠️ System complexity – requires compressors, controls, and skilled operation.
⚠️ Higher cost – more expensive than standard foam systems in both installation and maintenance.
⚠️ Training requirement – firefighters must be trained to handle CAFS effectively.
⚠️ Foam concentrate compatibility – not all concentrates work efficiently in CAFS.
Both normal foam and compressed air foam systems have unique roles in firefighting. Normal foam systems are well-suited for large-scale hydrocarbon fires and industrial hazards, while CAFS offers superior performance in structural, wildland, and confined-space firefighting due to its efficiency, cooling effect, and adhesion.
When selecting between the two, decision-makers must consider hazard type, scale of fire risk, system cost, and operational requirements. In many cases, a hybrid approach—using normal foam for bulk fuel hazards and CAFS for Class A and tactical firefighting—provides the most comprehensive fire protection.
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