These Reusable Pollen Filters are genuine Philips Respironics replacement filters compatible with all DreamStation 2 CPAP and BiPAP machines. A foam filter must always be installed while the device is in use. Usage: Clean the filter every two weeks, or sooner if it becomes dirty. Replace it every six months or sooner if it becomes damaged. Note: The white filter media is permanently attached to the gray filter housing and is not designed to be separated.