You can control the humidity using the control dial on the dehumidifier. The Digital display unit displays the current humidity level in % RH. You can set the humidity by turning the knob clockwise or anti-clockwise, clockwise toward red zone represent stronger moisture absorbing estimate reading of humidity level at 35-40%. Green LED light turns brighter and dimmer when knob is turned clockwise/anticlockwise. Red LED shows power is on. Anti-clockwise towards Green Zone represents weaker moisture absorbing, estimated humidity reading at 50-70%. We will recommend to start setting the dial at blue zone for a humidity level of 40 to 55%. Remark: Humidity reading display at each setting point varies depends on sizes and different products stored inside the cabinet as well as ambient temperature where the cabinet is situated.