The answer to this question is, if needed, yes, BUT ONLY use a humidifier on the high volume side of the reservoir. An example of this humidifier is pictured below. This is different than the humidifier that is often attached to the Air Separator. We recommend that you DO NOT use a humidifier between the Air Separator and the reservoir.
Remember, humidifier chambers must be drained daily and then washed with soapy water and disinfected with a vinegar/water (1 to 4) solution on a weekly basis. After disinfecting, rinse well with warm water and allow to air dry before use.