National Foam Proportioners utilize the water flowing through them to produce a venturi effect that induces foam concentrate into the water stream.

Line Proportioners
Line Proportioners are venturi devices that introduce foam concentrate into a flowing stream of water at a controlled proportioning rate. The line proportioner (also known as an inductor or eductor) is a simple, inexpensive method of proportioning when the water supply pressure is reasonably high. It has no moving parts and requires minimal maintenance.

Ratio Controllers
The Ratio Controller is a modified venturi proportioning device designed to inject foam concentrate into the water supply piping. It is compatible with all types of foam fire protection systems, and proportions all types of foam concentrates over their entire flow range without manual adjustments, regardless of pressure. Ratio controllers are available in threaded (RCT), flanged (RCF), or wafer (RCW) style.