Most CPAP accessories are interchangeable between different machine types and models, but it’s important to double-check compatibility. The majority of CPAP masks are universally compatible, so they can work with almost any CPAP, APAP, or BiPAP machine. That said, there are a few exceptions. A few CPAP models only work with certain types of masks. Standard 19-millimeter tubing is compatible with nearly all PAP masks and machine varieties. However, certain models can only be used with a slim 15-millimeter hose.