Every CPAP machine needs a filter to clean the air that you breathe, whether it’s from bacteria, dust or other impurities. There are three different types of filters: reusable, disposable and bacteria filters. Reusable foam filters catch larger particles and must be washed; however, they last for around 3 months or until the foam starts to degrade. Disposable fine filters should be changed at least once a month, unless you are in a dusty environment and then they should be changed more often. Bacteria filters are fine enough to catch some bacteria and are mostly used to prevent sinus infections or the exchanging of bacteria when people share a CPAP mask. If you can see any matter on the bacteria filter, you should throw it away and buy a new one. If you use a humidifier, make sure to air your filter out during the day so that bacteria does not begin to grow on it. The PhilipsRespironics brand created a reusable filter for its DreamStation CPAP machine. It also created multiple different disposable filters for the DreamStation. While there are many different filters for CPAP machines to choose between, keep in mind what purpose you want your filter to serve and how often you are willing to change it when you purchase a filter.