Your HVAC filter loads up with dust, pollen, and allergen particles and becomes a flow restriction — your system works harder, your energy bills climb, and the air you're breathing is worse than if you had no filter at all. A clogged filter doesn't filter, it just slows. 14 x 25 x 1 inch Filtrete Allergen Defense filter, MPR 1000 (Microparticle Performance Rating). Electrostatic filter media uses an electric charge to actively attract and capture allergens — pollen, dust mite debris, pet dander — out of the air stream before they circulate through your duct system. 1-inch depth is the standard filter thickness for most residential split systems and air handlers — easy to install, easy to replace on a seasonal schedule. The Filtrete brand is what most homeowners and property managers recogn Stocked at Crofton Lumber and Akron Lumber.