Every air purifier model is different, so carefully read the instructions on how to properly clean and care for it. Some HEPA filters are washable, and you can clean or soak them in water and reuse them. However, some reusable options are non-washable, and you may need to vacuum them instead. Homer suggests cleaning any metal-screen pre-filters with water or a vacuum. She notes that most disposable HEPA filters typically need to be replaced approximately every three months rather than washed and re-used. To clean your air purifier’s exterior, Homer recommends using a microfiber towel lightly dampened with your favorite all-purpose cleaner. If you need to clean the interior, she warns that most manufacturers caution against using soap on any internal parts of the purifier since soapy residue attracts dust and may clog up the machine. Regardless of whether you wash or replace your air purifier's filter, be sure to turn it off and unplug it before removing the filter.