Change your CPAP filter every one to three months, depending on the filter type and your environment

Most CPAP machines use one of two filter types: disposable foam filters that need replacement every month, or reusable filters that last two to three months before washing and eventual replacement. The exact interval depends on whether you have pets, live in a dusty area, or have allergies — all of which clog filters faster. Your machine's manual will specify the recommended schedule for your model, but the practical rule is simpler: if the filter looks gray or clogged when you hold it to the light, it is time to change it, regardless of the calendar.

Waiting too long between changes reduces the machine's ability to filter air, forces the motor to work harder, and can push unfiltered dust into your lungs. A clogged filter also makes the machine louder and less effective at delivering the pressure your therapy requires. Changing it on schedule is one of the cheapest maintenance tasks you can do to keep the machine running and protect your health.

Key Takeaways

  • Disposable foam filters need replacement every month; reusable filters need washing every two to three months and replacement once yearly.
  • Pets, dust, and allergies speed up filter clogging, so check your filter monthly even if the schedule says longer intervals.
  • A gray, discolored, or visibly clogged filter should be replaced when ready, regardless of how long it has been in use.
  • Replacement filters cost between $15 and $40 per pack, depending on your machine model and whether you buy from the manufacturer or a third-party supplier.
  • Most machines have a filter change reminder light or counter that alerts you when the scheduled interval has passed.

Disposable filters: monthly replacement

If your CPAP uses a disposable foam filter, plan to replace it every month. These are the most common filter type on entry-level and mid-range machines. They are designed to be thrown away after use, not washed or reused.

Disposable filters are inexpensive — usually $15 to $25 for a pack of two or three — and straightforward to swap out. You remove the old filter, slide in the new one, and reset the filter counter on your machine's display. The downside is the ongoing cost and waste if you are changing them monthly year-round.

If you live with pets, smoke indoors, or have significant dust or pollen in your home, your disposable filter may clog before the month is up. Check it every two weeks by holding it to a light source. If you see gray dust or the filter appears dark, replace it early.

Reusable filters: washing and replacement schedule

Reusable filters are made of thicker material and can be washed and dried for reuse. They typically last two to three months before needing a wash, and you can reuse them for about a year before replacing them entirely. Machines that include reusable filters often cost more upfront but save money over time.

To wash a reusable filter, remove it from the machine and rinse it under warm tap water. Use your fingers to gently rub away visible dust and debris. Do not use soap or scrub hard — you can damage the filter material. Shake off excess water and lay it flat to air dry completely before putting it back in the machine. This usually takes two to four hours.

After about a year of washing and reuse, the filter material degrades and no longer traps particles as well. At that point, order a replacement filter for your machine model. A new reusable filter costs $25 to $40, but because you use it for a year, the monthly cost is lower than disposable filters.

Signs your filter needs changing now

Do not wait for the calendar or the machine's reminder if your filter shows these signs: the filter appears gray, dark, or visibly clogged with dust; you see debris when you hold it to light; the machine is noticeably louder than usual; or you notice reduced air pressure or comfort during therapy.

A clogged filter forces your machine's motor to work harder to push air through, which shortens the motor's lifespan and uses more electricity. It also means unfiltered air is reaching your airway, which defeats the purpose of the filter. If you have allergies or asthma, a dirty filter can trigger symptoms even while you are using the machine.

If you are unsure whether to change the filter, change it. The cost of a replacement is far less than the cost of a new machine or the health impact of breathing unfiltered air for weeks.

Factors that speed up filter clogging

Your filter will clog faster than the standard schedule if you have pets in your bedroom, live in a dusty or dry climate, or have untreated allergies. Pets shed hair and dander that clogs filters quickly — if you sleep with a dog or cat, plan to change disposable filters every two to three weeks instead of monthly. Dry climates and dusty environments (construction sites, unpaved roads nearby, or poor air quality) also accelerate clogging.

If you use a humidifier with your CPAP, check the filter more often. Humidifiers add moisture to the air, which can cause dust and debris to stick to the filter faster. Some people find that using distilled water in the humidifier reduces mineral buildup and filter clogging, though it does not eliminate the problem.

Smoking indoors or living with someone who does will clog your filter much faster. Smoke particles are tiny and sticky, and they accumulate on the filter within days. If possible, smoke outside or in a separate room away from your CPAP machine.

Where to buy replacement filters

Replacement filters are sold by the machine manufacturer, medical supply companies, and online retailers. Manufacturer filters are usually the most expensive but may provide to fit your exact model. ResMed, Philips Respironics, and Fisher & Paykel all sell filters directly through their websites or authorized dealers.

Third-party suppliers like Amazon, CPAP.com, and local medical supply stores often sell compatible filters at lower prices. Before ordering from a third-party seller, confirm the filter model number matches your machine — the model is printed on your machine's case or in the manual.

Some insurance plans cover CPAP supplies, including filters, if you have a prescription for CPAP therapy. Check with your insurance company or ask your sleep clinic whether filters are covered. If they are, you may be able to order them through a DME (durable medical equipment) supplier at no cost or a small copay.

Setting up a filter change routine

The easiest way to stay on schedule is to set a phone reminder for the first of each month (for disposable filters) or the first of every other month (for reusable filters). When the reminder goes off, check your filter. If it looks clean, note the date and check again in two weeks. If it looks clogged, replace or wash it when ready.

Keep a spare filter or two on hand so you are never without a clean one. Disposable filters are cheap enough to stock, and having a backup means you do not have to rush an order if your filter clogs unexpectedly. Store spare filters in a dry place away from direct sunlight.

Most CPAP machines have a built-in filter change counter or reminder light. When you replace the filter, reset this counter according to your machine's manual. The reminder will alert you when the next change is due, though you should still visually inspect the filter between reminders.

Frequently Asked Questions

What happens if I do not change my CPAP filter?

A clogged filter reduces air flow, forces your machine to work harder, and allows dust and particles to reach your airway. Over time, this can trigger allergies, reduce therapy effectiveness, and shorten your machine's lifespan. The motor may also overheat or fail if it is forced to push air through a severely clogged filter.

Can I wash a disposable filter instead of replacing it?

Disposable filters are not designed to be washed and reused. The foam material breaks down when wet and loses its ability to trap particles. Washing a disposable filter will damage it and make it less effective. If cost is a concern, ask your supplier about switching to a reusable filter model instead.

How do I know which filter type my machine uses?

Check your CPAP machine's manual or the filter itself. Disposable filters are usually thin foam and come in a plastic case. Reusable filters are thicker, often white or gray, and are designed to be removed and washed. Your machine's model number is printed on the case — you can also search this number online to find the filter type and cost.

Do I need to replace the filter if I only use my CPAP a few nights a week?

Yes. Even light use exposes the filter to dust and debris. Change disposable filters monthly and wash reusable filters every two to three months regardless of how many nights you use the machine. If you store your machine unused for weeks, inspect the filter before using it again.

Can I use a generic filter instead of the brand-name one?

Generic and third-party filters work well if they match your machine's model number exactly. They are usually cheaper than brand-name filters. Before ordering, confirm the part number on the filter packaging matches the number in your machine's manual. If the numbers do not match, do not use it — an incorrect filter may not fit or seal properly.