3M's Filtrete 20-in x 24-in x 1-in air filter captures airborne microparticles, including smoke and smog, as well as airborne allergens such as pollen, mould spores, and pet dander. It has a lifespan of 90 days, so you won't have to change it before 3 months. Plus, it boasts a 1000 Microparticle Performance Rating (MRP 1000). This product also meets the American Lung Association Health House Indoor Air Quality Guidelines. It even outperforms other 1-inch filters that have the same lifespan. This filter is free of unnecessary antimicrobial chemicals, which means that it's a safe-to-use product that will provide you with great air quality. The Filtrete filtering material prevent the growth of mould, bacteria, fungi, and mildew when used as indicated.