sectional view of the nozzle 34 and its connections to the air heater 32 and the supplemental inlet line 48 a main air passage 36 connects the air heater 32 to the nozzle 34 passage 36 connects with a premix chamber 38 which directs air through a flow straightener 40 and into a mixing chamber 42 temperature and pressure of the air or other heated main gas are monitored by a gas inlet temperature thermocouple 44 in the passage 36 and a pressure sensor 46 connected to the mixing chamber 42 the mixture of unheated high pressure air and coating powder is fed through the supplemental inlet line 48 to a powder injector tube 50 comprising a straight pipe having a predetermined inner diameter the predetermined diameter can range from 0 40 to 3 00 millimeters preferably it ranges from 0 40 to 0 90 millimeters in diameter the tube 50 has a central axis 52 which is preferentially the same as the axis of the premix chamber 38 the tube 50 extends through the premix chamber 38 and the flow straightener 40 into the mixing chamber 42 mixing chamber 42 is in communication with the de laval type nozzle 54 the nozzle 54 has an entrance cone 56.