Which statement accurately describes Induction foam proportioning?

• A. Foam concentrate is entrained into the water stream through a Venturi device at the nozzle
• B. Foam concentrate is mixed with water in a separate tank before deployment
• C. Foam concentrate is injected directly into the pump discharge
• D. Foam concentrate is premixed with water in a closed container before use

Answer: (A)

Induction foam proportioning relies on the Venturi principle to pull foam concentrate into the water stream as it flows through the nozzle. When water is forced through a narrow throat, its velocity increases and pressure drops, creating suction that draws foam concentrate from its reservoir into the flowing water. The concentrate mixes with the water right at the nozzle or within the eductor, producing the foam solution before it exits the nozzle. This method keeps the concentrate in a separate container and uses the water flow itself to achieve the correct foam-to-water ratio, without pre-mixing in a tank or injecting foam directly into the pump discharge. Premixing in a separate tank or injecting into the pump discharge describe different methods of proportioning that bypass the Venturi-entrainment mechanism characteristic of induction systems.