Safe Home Duo4 Air Pollution Filter for 4 or 5 Inch Furnace Slots 16 x 20 Inches SafeHome's most powerful disposable filter for HVAC systems up to 6 times the filtering power of SafeHome's one inch thick Duo furnace air filter. Replace 4 or 5 filters. The Duo4 traps hazardous chemicals, odors and allergens. This is a 16 by 20 by 4 inch thick furnace filter with both a pollen,dust, dirt filter and a VOC activated carbon potassium permanganate treated filter. Note Always check with your HVAC technician before changing from your current furnace filter. This unit is a MERV 8. Made in USA. Safe Home TM Duo4 filters are the only home air replacement filters to capture allergens, odors, and harmful chemicals. Gaskets around the edges mean 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 Duo 4 lasts 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 to trap 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 16 x 20 x 4 Note All furnace filters with external frames are made slightly smaller than the noted dimensions in order to fit into the furnace filter slots. This is an industry standard. Captures up to 95% of common household allergens Eliminates odors from pets, paint, cooking, and more Uses high density carbon and advanced compounds FormaldaSorb TM , a patented potassium permanganate product plus the activated carbon in t