The Optional K9-II There is the option to have a Variable Speed K9-II. It can be purchased as an addition to the Hanvey Tandem Dryers or as the only dryer. To use the K9-II, press the air bulb and then increase the air speed with the dial on the K9- II. To turn off the K9-II turn down the air speed dial (before the dial clicks off) and then press the air bulb to turn it off. The air bulb MUST be used to turn on and off the dryer. Note: Depending on the dryer setup in your conversion; if the air bulb is left “ON” for the K9- II either the Space Heater or Water Heater will be unable to power on.