Last verified 2026-08-16
Why your CPAP mask leaks, and what to change
It’s 2 a.m., air is blowing toward your eye, and tightening the straps feels like the obvious fix. Stop tightening.
A CPAP cushion seals by inflating slightly against your face while the machine is running. If you pull the headgear too tight, you flatten and distort the part that is supposed to inflate. The mask can leak more, not less, and you wake up with red marks on top of it.
Start over with the straps loose. Lie down in the position you normally sleep in, turn the machine on, and tighten the headgear a little at a time until the leak stops. Stop there. A properly fitted mask may feel much looser than you expect.
Fit it in bed, not standing at the bathroom mirror. The soft tissue of your face shifts when you lie down, so a mask that looks sealed while you’re upright can leak as soon as your head hits the pillow.
If loosening and refitting the mask doesn’t solve it, there are four common places to look next.
Cause 1: the cushion is worn out
Silicone changes with use. A cushion that sealed well 2 months ago can go slack, stiff, or slightly sticky. The change happens gradually, so it can feel like you suddenly forgot how to fit the mask when the problem is really worn equipment.
Run a finger along the sealing edge. If you have a new cushion, compare the two. The new one should feel smooth and springy and should return to its shape easily.
If your cushion is more than 2 months old and has started leaking, replacing it is a sensible first test. Insurance replacement schedules generally allow cushions to be replaced more often than many people replace them, and the cushion is also the least expensive part of the mask to change.
Cause 2: the cushion size is wrong
Your overall body size does not tell you what cushion size you need. A small person can need a large cushion and a large person can need a small one. The cushion size depends on the size and shape of the part of your face it has to seal around.
If the cushion is too small, it may sit on the sides of your nose instead of around it and leak sideways. If it is too large, it can slide as you move and lose its seal.
Sizing also changes from one mask line to another. A medium in one manufacturer’s mask is not necessarily the same as a medium in another, and some masks come in more than one width as well as more than one nominal size.
If your mask came with several cushion sizes, try the ones already in the box before buying anything. If none of them sits well, an in-person fitting through a supplier is useful.
→ Every mask we’ve documented, with its available cushion sizes
Cause 3: the mask design does not fit your face or the way you sleep
Sometimes the mask is adjusted correctly and still has the wrong geometry for you.
If you have a beard, a mask that seals across the lower cheeks or chin has to seal through facial hair. Nasal pillow and under-nose designs avoid much of that area and can be easier to seal.
If you sleep on your side or stomach, a bulky mask with a front-mounted tube can get pushed sideways by the pillow. Masks that route the tube over the top of the head are designed to reduce that problem.
If the bridge of your nose is sore or marked every morning, more strap tension is not the answer. Some masks do not touch the bridge at all. The same distinction matters if you need to wear glasses in bed.
Every mask page on this site includes a contact map showing where that model touches the face. Use it to rule out designs that conflict with your beard, pressure-sensitive areas, glasses, or sleeping position before you spend time comparing smaller differences between masks.
→ Mask finder — five questions, and we rule out what can’t work for you
Cause 4: the leak is through your mouth
A nasal mask can seal perfectly while air still escapes through your mouth. Waking with a very dry mouth is one of the clearest clues.
The usual pattern is that the mask feels well sealed, the machine still reports a significant leak, and your mouth is dry in the morning. In that situation, tightening the mask will not fix the source of the leak.
Talk with the clinician managing your therapy before buying equipment at random. Depending on why your mouth is opening, the options can include a full-face mask, a chin strap, or changes in humidification.
Work through the problem in this order
- Refit the mask while lying down, starting with the straps loose.
- Check the cushion’s age and condition and replace it if it is worn.
- Try the other cushion sizes you already have.
- Decide whether the mask design suits your face and sleeping position.
- If the mask seal looks good but the machine still reports leak, consider mouth leak.
Many leaks resolve in the first two steps. Those steps cost nothing or almost nothing.
When to stop adjusting the same mask
If you’ve worked through those steps and the mask still leaks, the mask may simply be a poor fit for you. Spending months tightening, padding, and repositioning one model can turn a mask problem into a reason to abandon CPAP.
Suppliers will often exchange a mask that is not working. Ask what exchange options you have before buying another one yourself.
If you stop using PAP, tell the clinician managing your sleep apnea rather than quietly stopping. Documented intolerance is often part of the coverage requirements for other treatment options later.
This page covers equipment fit. It isn’t medical advice, and pressure settings are prescribed by the clinician managing your therapy. A leaking mask is not a reason to change pressure settings on your own.
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