Ecoquest Breeze AT Air Purifier

Question

My Ecoquest Breeze AT Air Purifier has been humming along for two years. It gets cleaned as per the instruction manual. In the last month, the unit shuts itself off even though there is no break in power to the unit and the fuze is fine. When the power button is pressed, the unit will run fine for ten or fifteen minutes and then shut off again. Any ideas as to cause and correction??? Thank you, Mike