Manufactured in Canada, the Vortex 220 CFM VTX400P inline blower, for 4 in. Dia duct, has a built in automatic pressure switch that detects when air is flowing through the ventilation duct. It will automatically turn on and off the Vortex VTX400P inline blower as required. In a clothing dryer application, when the dryer goes on, the VTX400P will automatically turn on and will stay on till shortly after the dryer goes off. This will allow the dryer to perform better and more efficiently. Both, drying time and power consumption are therefore reduced. This dryer exhaust kit also comes with a Vari-Speed speed control.