LEARN · 5 MIN READ

CPAP mask leaking: read the leak graph, then fix it

A leaking CPAP mask is rarely a mystery once you look at when and how the leak happens. Each cause leaves a different shape in the leak graph: a steady high line, sharp spikes, a plateau that starts mid-night or a slow climb over weeks. Match your shape to the cause, then change one thing at a time.

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Read the shape first

Open last night's leak line and look at its shape before you change anything. Leak is measured in litres per minute. On a ResMed machine the figure is unintentional leak only, and ResMed treats anything above 24 L/min as a large leak. Our guide to CPAP leak rate explains the numbers, including why Philips machines report total leak and cannot be compared directly.

What the graph shows	Most likely cause	First fix
High all night, from the first minute	Poor fit or a worn cushion	Refit lying down, then replace the cushion
Short spikes that come and go	Position changes or the hose pulling	Manage the hose, check your sleep position
A plateau that starts after you fall asleep	Mouth leak on a nasal mask or pillows	Chin strap, or try a full-face mask
Leak that climbs over weeks	Cushion or headgear wear	Replace the cushion on schedule
Leak that rises when pressure rises	Strap tension or a seal that fails at higher pressure	Loosen, refit, try another size
Low leak, dry mouth in the morning	Mouth breathing	Same as mouth leak above

Fit

Masks are usually fitted sitting up, but your face changes shape when you lie down. Put the mask on, start the machine, lie in your usual position and adjust it there. Many machines have a mask-fit check that runs the pressure up so you can feel leaks around the edges. A steady high leak from the first minutes usually points here.

Cushion wear

Silicone softens and loses its shape with daily use. If your leak has crept up over a few weeks with no other change, the cushion is the first suspect. Many insurance plans cover a replacement cushion on a regular schedule, so check before you pay out of pocket. Mask fit and gear tracking in Apnealytics follows leak per mask, so you can see a cushion ageing.

Mouth leak

On a nasal mask or nasal pillows, air can escape through an open mouth once your jaw relaxes. In the graph it appears as a long plateau that starts some time after you fall asleep and clears when you roll over or wake. A dry mouth in the morning is the classic clue. A chin strap helps some people and others do better in a full-face mask. Discuss options with your clinician or equipment provider before using anything over your mouth.

Strap tension

It is tempting to crank the straps when you hear a hiss, but over-tightening folds the cushion and opens new gaps. Loosen the headgear until the mask just seals at full pressure. A good fit should not leave deep marks in the morning.

Pressure

As pressure rises, the force pushing the cushion off your face rises with it, so some masks seal at low pressure and leak at higher pressure. If your leak climbs when your pressure climbs, fit is the first thing to look at. Do not change your pressure settings yourself: that is a clinician's decision. See CPAP pressure settings explained.

When to try a different mask

If you have refitted, replaced the cushion and still leak, the mask may be the wrong size or style for your face. The free Mask Finder turns a few questions about how you sleep into a short list, and Choosing a CPAP mask explains the trade-offs. For a printable checklist of fixes to try tonight, read CPAP mask leaking? Seven fixes to try tonight.

FAQ

Questions people ask

Help center →

Why does my CPAP mask leak only at night?

Because your face and position change as you fall asleep. Leak that starts after you drift off often points to mouth leak or a shifting mask rather than fit when you are awake.

What is a normal CPAP leak?

Some leak is intentional: vent holes flush out exhaled air. On a ResMed machine, unintentional leak under about 24 L/min is below the large-leak line. Many people run well below it. Brief spikes during position changes are normal.

Can a leaking mask raise my AHI?

It can distort it. High leak makes events harder to detect, and ResMed marks apneas during large leak as unclassified, so a low AHI on a high-leak night should be read with caution.

How often should I replace my mask cushion?

Silicone wears with use, and many suppliers and insurers replace cushions roughly monthly to quarterly. Replace sooner if leak creeps up with no other change.

My leak is fine but my mouth is dry. Is that a leak?

It can be mouth breathing that the machine does not score as high leak, especially with a full-face mask or if your machine compensates. Mention it to your clinician.