The Quest 506 is equipped with two high efficiency MERV-13 media filters. We suggest you replace both filters at the same time. Quest 506 Dehumidifier MERV-13 air filter replacement measures in inches 20L x 18H x 2W. We recommend changing them every 3-6 months depending on conditions. For maximum life of your unit and cleanliness of your facility, Growers House staff recommends you change after every cycle of plants in a room to make sure you decrease back-pressure stress on the unit and eliminate potential cross contamination.
