What device draws foam concentrate from a container into a moving stream of water?

• A. Foam nozzle
• B. Foam pump
• C. Foam eductor
• D. Foam injector

Answer: (C)

Entraining foam concentrate into a moving water stream relies on a device that creates suction from the water flow to pull concentrate into the mixing area. The foam eductor achieves this using the Venturi effect: when water under pressure flows through the eductor, its velocity increases in a narrow throat, causing a drop in pressure that draws foam concentrate up from its container through a pickup line into the eductor’s mixing chamber. The concentrate then mixes with the water and travels downstream as foam solution.

This method is straightforward and reliable on fire apparatus because it uses only the water pressure to achieve mixing, with the rate controlled by the eductor’s design. The other devices don’t perform this suction-based entrainment in the same way: a foam nozzle can apply foam or inject concentrate but doesn’t draw concentrate from a container into the moving stream by itself; a foam pump moves concentrate but doesn’t create the suction needed to pull it into the water stream; a foam injector is similar in function in some systems but the standard, widely taught device for this purpose is the foam eductor.