Proven, Cost Effective Class A Foam-Making Systems for Urban and Wildland Firefighting Operations. CO-SON Industries variable round-the-pump Foam Proportioner is an effective, inexpensive low maintenance foam eductor which introduces foam on the suction side of most any fire pump. This foam metering (proportioner) device is to be plumbed between the discharge and suction side of the pump. Plumbing tees available.