The 3M Filtrete Micro Allergen Reduction filter has an actual size of 17.5 x 23.5 x 0.8125 inches, though it is labeled as a nominal 17.5x23.5x1. This 4-pack is designed to fit standard HVAC return vents and furnace slots requiring these exact dimensions. Always measure your existing filter before ordering to ensure a proper fit, as a correctly sized filter prevents air bypass and maximizes filtration performance in your system.

This 3M Filtrete Micro Allergen filter carries a Microparticle Performance Rating (MPR) of 1000, which is 3M's proprietary rating system. It is equivalent to a MERV 11 rating. The filter is specifically engineered to capture microscopic particles as small as 0.3 microns, including lint, dust mite debris, mold spores, pollen, pet dander, smoke, and smog particles that can trigger allergies.

3M recommends replacing the Filtrete Micro Allergen 1000 MPR filter every 90 days (3 months) for optimal performance. With this 4-pack, you have a full year's supply of replacement filters. Homes with pets, smokers, high dust levels, or frequent HVAC use may need to replace the filter more often—every 45 to 60 days—to maintain airflow and indoor air quality.

The Filtrete Micro Allergen Reduction filter uses 3M's exclusive Electrostatic Filtrete Brand Media to attract and trap microscopic airborne particles. It captures up to 90% of large airborne particles including household dust, pollen, mold spores, pet dander, dust mite debris, and lint. Unlike basic fiberglass filters, its electrostatic charge actively pulls particles from the air passing through your HVAC system.

The Filtrete Micro Allergen 1000 MPR filter is compatible with most residential central heating and air conditioning systems that accept a 17.5x23.5x1 filter. It features a durable pleated design with a reinforced beverage board frame to prevent bending or collapsing. The arrow on the filter frame should point toward the furnace or blower to ensure proper airflow direction during installation.