12 Poly-Wool Filter Pads for Envirosept HVAC Furnace Panel Model 2025 Twelve replacement furnace filter s for Envirosept Furnace Panel HVAC air purifier model 2025 Furnace Panel NOT included . Exact size is 18 inches by 22 inches. Note the actual physical size of the panel itself is not 20 x 25 but 19 1/2 x 24 1/2 x 1. Two replacement pads per filter change unless you remove dirtier pad and replace with cleaner on. Replace filter pads monthly or more often if needed. Note Measure the panel insert including the black plastic piece to get accurate dimensions of your Envirosept insert. Replacement furnace filter pads cover only the inside mesh part of the furnace air cleaner panel. Replacement furnace filters are made from a custom poly-wool blend of proprietary fibers without latex or adhesives. We suggest a label on your furnace to remind you of the size. To Replace Furnace Filters Unplug the unit. Remove furnace filter panel from the slot. Open the two retaining clips. Remove both filters. If desired, move the less dirty filter to where the dirtier filter was. Add second filter. Push the clips closed, slide panel into slot and plug in. This item ships from a separate warehouse and may require extra time for delivery.