You must remove the plastic cover from the activated carbon filter and install in the unit. Position the pre-filter the rear of the unit (closest to the electronic cell) and the carbon filter at the front side where the air comes out.

Make sure the electronic cell is properly placed in the cabinet - the airflow arrow on the end plate should be pointing toward the fan. Electronic air cleaners should not be placed in any area where potentially explosive gases or vapors exist. In addition, they should not be used in wet environments.

Visit BuyFriedrich.com for more details on the C-90B or to order replacement filters online.