While this pre-filter is designed to be compatible with the Blue 3210. For quick cleaning, use the brush attachment on your vacuum to clean the exterior of the fabric pre-filter of visible dust and dirt between washes. Designed to be reused when the pre-filter requires a deeper clean, washed on a gentle, low-temperature cycle in the washing machine. Hang to dry. A hidden velcro-panel in the fabric pre-filter holds the power cord, keeping it close to the body of the air purifier and out of sight. We designed our new premium fabric pre-filters in an earthy color palette inspired by our Swedish heritage and Scandinavia's natural landscape