This model was manufactured until the end of 2005, it has no outburst with compressed air.
9990 has the 240 VAC fan (item no. 612) where the air volume is adjusted with a damper mounted on the fan.
The circuit board that 9990 is equipped with is called ver. 2.0.
The screw motor is either Mellor or Crouzet, the former is available for purchase in the store.
The overheating protection is AirPax.