What is the purpose of a foam proportioner in an AFFF system?

• A. To heat water to improve foam mixing
• B. To blend foam concentrate with water at the correct ratio to achieve effective foam expansion and film formation
• C. To purify foam concentrate before use
• D. To regulate pH of water

Answer: (B)

The main function of a foam proportioner in an AFFF system is to mix the foam concentrate with water at the correct ratio so the resulting foam solution has the proper expansion and forms a stable film on the fuel surface. The concentrate contains surfactants and film-forming agents that only work effectively when diluted to the intended proportion. A properly proportioned mix expands into foam that blankets the fire, cools the fuel, and creates an aqueous film that helps suppress vapors. If the ratio is off, the foam can be too rich or too lean, reducing expansion, film formation, and overall extinguishing effectiveness.