We recommend never turning off the Puritii Air Purification System.
When the Air Purification System is turned off, it is not cleaning the air in your home or business. The product was specifically designed with an energy efficient DC motor to keep your energy costs low - in fact, running the Air Purifier on the low setting for an entire year without interruption would only cost about $5.26 on your power bill (assuming the national utility average of USD $0.12/kWh). So go ahead and turn it up to high or turbo when you are away so that you come home to the cleanest air possible. Then, if the noise is too much, turn it down to medium or low to maintain the clean air while you are nearby.