Keep your MSA3 air purifier working like new with this replacement filter made for the MSA3 and MSA3S series. The multi-layer filter combines a True HEPA layer and activated carbon to help capture dust, pollen, pet dander, smoke, and everyday household odors. It’s easy to install and fits perfectly, helping your purifier keep the air in your home fresh and clean. For best results, we recommend replacing the filter every 6–8 months depending on usage.