Of all the supplies that come with a CPAP machine, the filter is the cheapest and the most consequential — and the one users are most likely to forget. Filters cost a few dollars each. Replacing them on schedule is the single most effective thing you can do to keep airflow consistent, humidity dialed in, and the inside of your machine clean. Skipping replacements doesn't break the machine immediately; it slowly starves it of clean air until therapy suffers in ways most people attribute to other causes.
The short answer
Disposable pollen filters: every 2 weeks (3–4 weeks at most). Reusable foam filters: rinse weekly, replace every 6 months. Hypoallergenic ultra-fine filters: every 2 weeks.
Why the manufacturer schedule is the floor, not the ceiling
ResMed, Philips Respironics, and Fisher & Paykel all converge on roughly the same replacement guidance: every two weeks for disposable filters, every six months for reusable foam filters. These numbers come out of accelerated lab testing — the manufacturers run filters in controlled-air environments and measure airflow resistance and particle breakthrough over time. The schedule assumes a relatively clean home environment.
Real bedrooms aren't lab environments. Pets, carpeting, candles, woodstoves, wildfire smoke, construction, even seasonal pollen all shorten filter life. If your filter looks gray, brown, or visibly loaded with debris before the recommended date, replace it sooner. The cost is a few dollars; the cost of waiting is meaningfully reduced therapy effectiveness.
What happens when you don't replace on cadence
A clogged filter doesn't fail dramatically. It fails gradually, and the symptoms creep in over weeks:
- Drier airflow. The machine works harder to push air through the restricted filter, which lowers the relative humidity delivered to your mask. Many users compensate by turning their humidifier up — masking the symptom rather than fixing the cause.
- Quieter — then louder — fan noise. Early on, the filter dampens motor noise slightly. As it loads up, the motor strains and noise increases. If your CPAP has gotten progressively louder over a few months, the filter is the first thing to check.
- Higher reported leak rates. Some users see their machine-reported leak metric drift up when filters are overdue. The mechanism isn't fully understood, but the correlation is consistent.
- AHI creep. Long-term users on the same supplies often see their AHI score rise gradually. Mask cushion wear is the biggest culprit, but filter restriction contributes more than most clinicians credit it for.
Disposable vs. reusable: which one do you have?
The two main categories of CPAP filter aren't interchangeable, and the replacement cadence is different for each.
Disposable pollen filters
These are the thin, white or off-white filters that come pre-installed in most ResMed AirSense, AirCurve, and Philips DreamStation machines. They're made of a non-woven polyester or polypropylene fabric and are meant to be thrown away — not rinsed. Most ResMed filters are about 4×4 cm; Philips uses a slightly different rectangular shape. Manufacturer guidance is every 2 weeks for these. We sell ResMed AirSense compatible packs and DreamStation pollen filters — both built to OEM spec.
Reusable foam filters
Older ResMed machines (S9 series, some AirSense 10 variants) included a reusable gray foam filter that sits behind the disposable filter. The foam version is rinsable — manufacturer guidance is to wash it weekly in warm water and replace it every 6 months. Most current machines have eliminated the reusable element in favor of disposable-only stacks.
Hypoallergenic / ultra-fine filters
These are the "premium" option. They use a charcoal-impregnated weave (or, in Philips's case, a separate ultra-fine filter that pairs with the standard pollen filter) to catch finer particulates — pet dander, dust mite debris, smoke, mold spores. They cost roughly 50% more than standard filters but make a real difference if you have allergies, pets, or live in an area prone to wildfire smoke. Same 2-week replacement window.
Special situations that shorten filter life
Wildfire smoke and high-AQI days
Particulate-loaded air ages a filter dramatically faster. During a wildfire week, consider replacing weekly rather than biweekly. The same goes for active construction nearby or any extended period of indoor dust. Check the EPA's AirNow forecast if you're not sure what your area's air looks like.
Pets
Cats and dogs in the bedroom shed dander that ends up in CPAP filters. If you have a pet that sleeps in your bedroom, hypoallergenic filters are a meaningful upgrade, and biweekly replacement is closer to a floor than a ceiling.
Bedroom near a kitchen or smoking
Cooking fumes — especially from gas stoves, woks, or anything seared at high heat — and any tobacco or cannabis smoke in the home age filters very fast and leave odors that the filter passes into your airway. If either applies, weekly replacement is reasonable.
How to actually remember to replace them
The hardest part of filter replacement isn't the filter — it's remembering. The two approaches that work:
- Subscribe-and-forget. A monthly delivery of filters means they arrive on your doorstep without you tracking dates. Our filter-only plan is $25 per month and ships free.
- Calendar reminder. If you'd rather order one-off, set a recurring calendar event. Our replacement schedule generator builds a 12-month calendar you can import into Apple or Google Calendar in one click.
One non-obvious tip: when you swap your filter, write the date on the new filter in pencil. Some users prefer this to digital tracking because the filter itself is the reminder — you can see at a glance whether it's been three days or three weeks.
What about filter cleaning?
Don't clean disposable filters. Rinsing or vacuuming a disposable filter damages the fiber matrix and turns a $1.50 part into something worse than no filter at all. The only filter that's meant to be rinsed is a reusable foam filter, and even those are meant to be replaced every six months regardless of cleaning frequency.
If a UV-light or ozone "cleaner" claims it can extend filter life or substitute for replacement, treat the claim skeptically. Ozone-based cleaners have been flagged by the FDA for safety concerns and don't replace mechanical filtration.
Bottom line
Filters are the cheapest, most-skipped, most-impactful piece of CPAP maintenance. Replace disposables every 2 weeks; replace ultra-fine filters every 2 weeks; replace reusable foam filters every 6 months. Sooner is fine. Later is the cause of a surprising number of "my therapy stopped working" calls to sleep clinics.