A mixer using mechanical means to mix gas and air, neglecting entirely any kinetic energy in the gas and air, and compressing the resultant mixture to a pressure suitable for delivery to its point of use. A mixer in this group utilizes either a centrifugal fan or some other type of mechanical compressor with a proportioning device on its intake through which gas and air are drawn by the fan or compressor suction. The proportioning device can be automatic or can necessitate manual adjustment to maintain the desired air/gas ratio as rates of flow are changed.
