This Reusable Pollen Filter for DreamStation CPAP/BiPAP Machines is a washable and reusable for up to one to two years if well maintained, but can be replaced every six months if needed. This filter blocks dust from the motor and helps the ultra-fine filter last longer. The filter should be washed every two weeks for optimal performance and life span. The DreamStation uses this reusable, blue pollen filter and a light-blue ultra-fine filter that is disposable. The reusable blue filter screens out normal household dust and pollens, while the light-blue ultra-fine filter provides more complete filtration of very fine particles. The reusable blue filter must be in place at all times when the device is operating. The ultra-fine filter is recommended for people who are sensitive to tobacco smoke or other small particles.