Last verified 2026-08-15
Why your CPAP mask leaks, and what to change
It’s 2am, air is hissing across your eye, and you’ve tightened the straps twice.
Stop tightening. That’s almost certainly making it worse, and it’s the single most common mistake in CPAP therapy.
Mask leak has four causes. They look identical at 2am and have completely different fixes, so the useful skill is telling them apart.
First: over-tightening
A CPAP cushion seals by inflating slightly against your face. Air pressure does the sealing, not strap tension.
Pull the headgear tight and you deform the cushion, flattening the part that’s supposed to inflate. The seal gets worse, so you tighten more, and the cushion deforms further. People end up with straps cranked down, red marks on their face, and worse leak than they started with.
What to do instead: loosen the headgear until it’s clearly too loose and leaking freely. Lie down in your sleeping position, turn the machine on, and tighten in small increments only until the leak stops. Stop there. The mask should feel barely attached.
Do this lying down, not standing at the bathroom mirror. Facial tissue moves when you lie down, and a mask fitted upright will not fit the same way in bed.
If that fixes it, you’re done. If it doesn’t, keep reading.
Cause 1 — the cushion is worn out
Silicone loses its shape. A cushion that sealed fine two months ago can stop sealing entirely, and the change is gradual enough that people blame themselves.
How to tell: run a finger around the sealing edge. A tired cushion feels slack, stiff, or slightly sticky rather than smooth and springy. Compare against a new one if you have one — the difference is usually obvious once you feel it.
The fix: replace the cushion. Most insurance replacement schedules assume cushions are replaced far more often than most people actually replace them. If yours is older than a couple of months and leaking, that’s your answer before anything else.
Cushions are also the cheapest thing to change, which makes them the right first test.
Cause 2 — wrong cushion size
Cushion sizing is not related to your overall build. Small people need large cushions and vice versa; it depends on the dimensions of your nose or the width of your mouth.
How to tell: too small and the cushion sits on the sides of your nose rather than around it, leaking sideways. Too large and it slides, leaking as you move.
Sizes are also not consistent between masks. A medium in one manufacturer’s range is not a medium in another’s, and some ranges include widths as well as sizes.
The fix: get sized properly, ideally in person by a supplier. Many masks ship with more than one cushion size in the box — check what you already have before buying anything.
→ Every mask we’ve documented, with its available cushion sizes
Cause 3 — the mask type is wrong for your face or your sleep
This is the one that requires an actual change rather than an adjustment, and it’s the one people take longest to reach.
Beards. Any mask that seals across your chin or lower cheeks is fighting facial hair. Nasal pillow and under-nose designs avoid that area entirely.
Side and stomach sleeping. A bulky mask with a front-mounted tube gets pushed out of position by the pillow. Masks with the tube routed over the top of the head are designed around this.
Sores on the bridge of your nose. Some masks contact the nose bridge; others don’t touch it at all. If you have pressure marks there, that’s not a fit problem to solve — it’s a reason to switch to a design that doesn’t go there.
Glasses in bed. Same principle. If the mask sits on the bridge of your nose, glasses won’t.
We show a contact map on every mask page — a face diagram marking exactly where that mask touches. It’s the fastest way to see whether a mask is even physically compatible with your situation.
→ Mask finder — five questions, and we rule out what can’t work for you
Cause 4 — mouth leak
If your mask is nasal and you wake with a bone-dry mouth, the air isn’t leaking around the seal. It’s going in your nose and out your mouth.
How to tell: the mask fits fine, the machine reports leak anyway, and your mouth is dry every morning.
What to do: this one is a conversation with your clinician rather than a purchase. The options — a full face mask, a chin strap, humidification changes — depend on why your mouth is opening, and that’s worth understanding before buying equipment to work around it.
The order to work through
- Loosen everything and refit lying down
- Check the cushion’s age and condition — replace if in doubt
- Try the other cushion sizes you already own
- Check whether the mask type suits your face and sleeping position
- If the seal is fine but leak is reported, consider mouth leak
Most leaks resolve at step one or two, and cost nothing or almost nothing.
When to stop adjusting
If you’ve worked through all five and it still leaks, the mask is wrong for you. That’s information, not failure.
People routinely spend months fighting a mask that was never going to seal on their face, and then conclude CPAP doesn’t work for them. It’s worth saying plainly: abandoning therapy over a mask that doesn’t fit is abandoning it for a solvable reason. Suppliers will often exchange a mask that isn’t working. Ask.
And if you do stop, tell your clinician rather than simply stopping — documented intolerance is what opens the door to other treatments being covered.
This page covers equipment fit. It isn’t medical advice, and pressure settings are prescribed by the clinician managing your therapy — not something to change because a mask is leaking.
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