If you breathe through your mouth on a nasal mask or nasal pillows, air escapes through your lips. That’s mouth leak, and it causes dry mouth, noise and high leak readings. There are three ways to deal with it: a chin strap, a full face mask, or, most controversially, mouth tape.
The options compared
| Option | What the evidence and guidance say | Cost / coverage |
|---|---|---|
| Chin strap (with a nasal mask or pillows) | AASM: “may help keep the mouth closed and reduce the air leak”. ATS and ResMed list it too | Medicare: 1 per 6 months (A7036) |
| Full face mask | AASM, ATS and ResMed all list it as the alternative for mouth breathers | Medicare: 1 per 3 months (A7030). Retail $155–$167 for ResMed F20/F30i |
| Mouth taping | 2025 systematic review: low-quality evidence, possible benefit only in mild OSA in a few studies, risk of asphyxiation with nasal obstruction | Not a PAP accessory |
Sources: AASM PAP troubleshooting FAQ, American Thoracic Society tip sheet, ResMed AirSense 11 user guide, CMS LCD L33718, ResMed shop.
Chin straps
A chin strap supports the jaw so your mouth stays closed while you use a nasal interface. The AirSense 11 user guide’s fix for a very dry mouth reads: “Air may be escaping through your mouth. You may need a chin strap to keep your mouth closed or a full face mask.”
Tips:
- Use it with a nasal mask or pillows, not a full face mask.
- If you still have mouth leak with the strap on, check your machine’s leak figure (mask leaks).
- Medicare covers one every 6 months as a PAP accessory (supplies schedule).
Full face masks
If a chin strap doesn’t stop the leak, or your nose is often blocked, a full face mask lets you breathe through either. ResMed’s troubleshooting guide suggests switching to a full face mask such as the AirFit F20 when there’s a mouth leak. See best CPAP masks for the F20 and the minimal-contact F30i.
Mouth taping: what the research found
The 2025 review by Rhee and colleagues in PLOS One (full text; PubMed):
- Scope. It searched MEDLINE, Embase and Google Scholar from February 1999 to February 2024. 10 studies met the inclusion criteria, with a total of 213 patients.
- Benefit. “Two studies showed statistically significant improvement in established markers of sleep apnea such as apnea-hypopnea index (AHI) or oxygen desaturations.” Other studies “showed that mouth taping offered no differences”.
- Risk. Studies “discussed potential risks including asphyxiation in the presence of nasal obstruction”, and many excluded anyone with nasal obstruction.
- Conclusion. “There is a potentially serious risk of harm for individuals indiscriminately practicing this trend. Further studies are required.”
Mouth taping is not a CPAP accessory, isn’t in Medicare’s PAP accessory list, and isn’t a substitute for treating sleep apnea. If you’re considering it, especially with any nasal blockage, talk to your sleep clinician first. If congestion is why you breathe through your mouth, treat it (nasal congestion).
Verdict
For mouth leak on a nasal mask or pillows, try a chin strap first. If that doesn’t work, switch to a full face mask. Both are standard, guideline-listed options that Medicare covers. Leave mouth tape alone unless your sleep clinician recommends it: the best evidence so far is weak, and it carries a real risk if your nose is blocked.