Which of the following is the other low-energy foam proportioning system installed on ARFF apparatus?

• A. Direct-injection
• B. Balanced pressure
• C. Venturi
• D. Eductor

Answer: (B)

Foam proportioning on ARFF apparatus can be high-energy or low-energy. Low-energy systems rely on the water supply pressure to mix foam concentrate with water, rather than using a dedicated high-pressure pump to push the concentrate into the line. Balanced-pressure foam proportioning is one of these low-energy methods. It meters foam concentrate into the water stream by maintaining closely matched pressures between the water line and the concentrate line, using a metering device to set the desired foam-to-water ratio. This allows a stable mix across a range of pump pressures and water flows, without adding significant energy into the discharge. That robustness and simplicity make it a common “other” low-energy option on ARFF units, alongside direct-injection systems which are high-energy. While venturi and eductor methods also use suction from the water stream to draw concentrate, the context here identifies the other low-energy system installed as balanced-pressure.