Sleep data and AHI
CPAP High Leak Rate: What Your Leak Number Means and How to Fix It
Your machine reports leak because every mask vents air on purpose, and it estimates any extra air escaping around the cushion or out of your mouth. A high leak warning or poor mask seal score usually means the mask fit, a dirty or worn cushion, mouth leak, or a loose tube or humidifier part. Fix the mask first, then check the connections.
Signs
- Poor mask seal score or high leak message
- Hissing around the cushion or air blowing in your eyes
- Dry mouth on waking
- Humidifier water running out early
- AHI higher on high leak nights
Common causes
- Mask fit and position
- A mask that fits poorly, is put on wrong, or shifts when you lie down leaks. ResMed suggests fitting the mask while lying down.
- Mouth leak
- Breathing through your mouth with a nasal or pillows mask lets air escape.
- Dirty or worn cushion
- Oils and wear stop the cushion from sealing.
- Loose tube or humidifier parts
- The AirSense 11 shows 'High leak detected' messages when the humidifier tub or side cover is not inserted properly or the tubing is not connected. The DreamStation 2 manual lists a missing or unseated water tank lid seal as a cause of leak or whistling sounds.
Fixes to try, easiest first
Check the connections
Make sure the tube is firmly connected at both ends and the humidifier tub and lid or side cover are fully seated and clicked in.
Run Mask Fit
If your machine has a Mask Fit function, run it lying in your sleep position and adjust until the seal reads good.
Reseat the mask instead of tightening
Loosen the straps slightly, pull the mask a little away from your face with the air on, and let it settle. Overtightening can make leaks worse.
Wash the cushion daily
Clean the cushion each morning with mild soap and water.
Handle mouth leak
A chinstrap or full face mask can help if you breathe through your mouth.
Replace worn cushions and headgear
Old parts lose their seal. Keep to your replacement schedule.
Ask for a refit with your clinician
If leak stays high, ask your equipment provider to check your mask size and style.
Call your equipment provider if leak stays high after refitting, cleaning and checking parts. Talk to your doctor if high leak comes with a rising AHI or returning symptoms such as sleepiness, since leaks can reduce the effectiveness of therapy. Do not change your pressure to compensate.
Supplies that can help
A soft strap that supports the jaw to help keep the mouth closed, used mainly with nasal and nasal pillow masks to reduce mouth leaks.
Pre-moistened wipes for a quick daily wipe of the mask cushion, mostly to remove skin oils between proper washes.
A pillow with cutouts or a contoured edge so a mask and hose are not pushed out of place when you sleep on your side.
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Mask types this applies to
Frequently asked questions
What is a normal CPAP leak rate?
Every mask leaks some air through its vent on purpose, and machines report leak in different ways. ResMed's myAir gives up to 20 points for minimal leak and fewer for moderate or high leak. Ask your equipment provider what range is acceptable for your machine and mask.
Why does my machine say high leak when my mask feels fine?
Check the tube connections and humidifier parts. A tub or side cover that is not seated can trigger leak messages on the AirSense 11. Mouth leak can also cause high readings without you feeling air around the mask.
Does a high leak make CPAP less effective?
It can. ResMed notes air escaping the mask means you may not get all the pressure you need to keep your airway open. Fixing the leak usually comes before any other change.
Sources
Last reviewed October 11, 2026. How we research · Report an error