Why your mask doesn't fit yet (and it's probably not the size)

Part of the series: The Complete CPAP Guide

Most first-week mask leaks trace back to headgear tension, not cushion size. A quick way to tell the difference.

The instinct when a mask leaks is to size up the cushion. In our experience fitting new CPAP users, that's the wrong first move more often than not — over-tightened headgear is the more common culprit, and sizing up a cushion on top of it just adds bulk without fixing the seal.

A quick diagnostic: with the mask on and the machine running at pressure, loosen the headgear straps until you feel a small leak start, then tighten just until it stops. If you're tightening well past that point to get a seal, the cushion size or shape is probably wrong — not the strap tension.

Side sleepers see this most: a mask fitted while lying on your back can seal perfectly and then leak the moment you roll over, because the cushion's contact angle against the pillow changes. That's a shape problem, not a size problem — worth trying a minimal-contact nasal design before assuming a full-face mask is required.

Our 90-day fit guarantee exists because of exactly this — the first cushion size someone tries is right maybe half the time. Exchanges are free and don't require sending the frame back, only the cushion.

This article is general health information, not medical advice, and doesn’t replace evaluation by your own physician. Talk to a doctor about anything specific to your own diagnosis or treatment.

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Sleep HealthJanuary 30, 2026·4 min read

By the CIRRUS Editorial Team — how we write and source this

Why your mask doesn't fit yet (and it's probably not the size)

Part of the series: The Complete CPAP Guide

Most first-week mask leaks trace back to headgear tension, not cushion size. A quick way to tell the difference.

This article is general health information, not medical advice, and doesn’t replace evaluation by your own physician. Talk to a doctor about anything specific to your own diagnosis or treatment.