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

• A. Direct-injection
• B. Venturi injector
• C. Automatic bypass
• D. Coaxial eductor

Answer: (A)

Direct-injection is a low-energy foam proportioning method because foam concentrate is metered and injected directly into the pump discharge without relying on the water’s energy to draw the concentrate in. A dedicated injector and metering device deliver the foam at a set ratio as the water passes through the discharge, so there’s minimal pressure loss and stable foam mix across flow rates. This simplicity and reliability make it a common choice on ARFF apparatus, where consistent performance at varying demands matters. By contrast, venturi injectors and coaxial eductors rely on the fluid’s energy to entrain concentrate, which introduces more pressure loss and variability. Automatic bypass is a control feature, not the primary proportioning method, so it doesn’t define the system type.