HVAC Furnace Filter is 4 x 20 x 20 Inches for Dirt, Odors and Chemical Removal For modern HVAC furnace systems , the Safe Home Duo 4 inch furnace filter MERV 8 is your best choice for clean, less polluted air. Safe Home's most powerfu l air filter for dirt, chemical fumes and other odors. Note Check with your HVAC technician to verify that your system is able enough to handle the density of a MERV 8 filter before purchasing this or any other MERV 8 filter. Install this MERV 8 with Air Flow First Going through the White Media. Made in USA. HVAC filter has up to 6 times the capacity of the one inch Duo furnace filter. Replaces 4 or 5 filters. SafeHome Duo4 traps hazardous chemicals , odors and allergens. Air purifier filter is 20 by 20 by 4 inches thick. Easily slides into an HVAC 4 or 5 inch filter slot. Note All furnace filters are made slightly smaller than the noted dimensions in order to fit into the furnace filter slots. This is an industry standard. The Safe Home TM Duo4 looks different the superior design has self sealing edges for maximum effectiveness at capturing allergens, odors, and chemicals from the air in your house. Use for furnace filter slots, temporary needs, or custom sizes in air return grills. The Duo4 replaces any 4 thick home air filter in any location and can last up to 9 months. How does the Duo4 work? The polyester outer layers remove pollen, mold spores, and other common allergens. The inner layer features FormaldaSorb TM and activated carbon that traps a variety of odors and hazardous gasses, such as formaldehyde, ammonia, and others that are emitted by cleaning chemicals, paint, particle board, and other household items. No other filters are as effective at removing dust mites, mold spores, pollen, odors, cleaning chemicals, ozone, paint fumes, and common gasses like formaldehyde which triggers asthma and allergies. Safe Home Duo4 Filter Features Dimensions 20 x 20 x 4 Captures up to 95% of com This item ships from a separate warehouse and may require extra time for delivery.