Which foam proportioning method uses an external pump or head pressure to force foam concentrate into the fire stream at the correct ratio for the water flow?

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Foam proportioning is about getting the right amount of foam concentrate into the water stream so the final mix stays at the intended ratio as water flow changes. The described method uses an external pump or head pressure to push the foam concentrate into the fire stream, which is exactly how injection works. By applying pressure to move concentrate from its reservoir into the water line, the system meters and injects the concentrate to maintain the correct foam-to-water proportion regardless of flow rate. This contrasts with eduction, which relies on the water flow’s velocity through a venturi to entrain concentrate; premixing, where concentrate is blended with water before discharge; and ejection, which isn’t a standard method here.