Universal Fit; Easy Installation; Replace every 2-4 weeks Q: Does this work with any CPAP machine? A: Yes! Our Filters are universal and work with all CPAP machines and tubes. Q: Does this work with Bilevel Machines? A: Yes! Our Filters are universal and work with all Bilevel CPAP machines and tubes. Q: What if I use a climate controlled tube? A: If you're using a climate controlled tube then connect the filter between the mask and the tube instead of the CPAP machine and the tube. Q: Will this restrict my CPAP's air flow pressure? A: CPAP pressures remain unaffected making sure you get the best out of your CPAP therapy while also breathing clean air. Q: How often should I replace them? A: Filters should be swapped out every 2 to 4 weeks. Depends on how dirty it gets.