Replacing your machine's filters is a quick and easy way to get fresher air.
All CPAP machines have a filter. It is located at the air intake at the back of the machine.
When using both a reusable and a disposable filter, the thin disposable filter will go in first, and the thicker, reusable filter will go in last. This way the reusable foam filter can get the larger particles and the disposable filters can catch the finer debris.