The indirect injection system of CON-V-AIR makes it possible to prepare a variable concentration solution in an overflow tank. In this system, water is used as the transport medium and it is by varying the speed of rotation of the screw that it is possible to increase or decrease the outflow. Since this system is an indirect one, when the operator changes the speed of the auger, there will be some delay before the new flow rate is reached (unlike our direct injection system which allows a much faster flow rate fluctuation).