Most CPAP machines use two types of filters, and only one of them can be cleaned. The reusable foam filter should be washed weekly with warm, soapy water. The disposable paper filter cannot be washed and needs to be replaced every one to three months. Knowing which is which, and how to care for each, keeps your air clean and your machine running well.
Two Filter Types, Two Different Rules
Your CPAP likely has a foam filter, a disposable paper filter, or both stacked together in the same slot. They do different jobs. The foam filter is a thicker, spongy rectangle that catches large particles like dust and pollen. The disposable filter is a thinner, white sheet made of fine mesh paper designed to trap much smaller particles, including tobacco smoke.
The foam filter is the one you wash. The disposable paper filter is never washed. Water breaks down its fine fibers and destroys its ability to capture small particles. If you’ve been rinsing both, you’ll want to stop and replace that paper filter right away.
How to Clean a Reusable Foam Filter
Once a week, remove the foam filter from the back of your CPAP machine. Most slide or pop out without tools. Soak it in warm water with a small amount of mild, fragrance-free dish soap. Gently squeeze the foam a few times to work soapy water through it, loosening trapped dust and oils. Don’t twist or wring it aggressively, as foam tears easily when saturated.
Rinse the filter thoroughly under warm running water until no soap residue remains. Soap left behind can release fumes when heated by the machine’s airflow, and those fumes end up in the air you breathe. Once rinsed, press the filter gently between the folds of a clean towel to blot out excess water. Then set it on a dry towel in a well-ventilated spot to air dry completely. Keep it out of direct sunlight, which can degrade the foam over time.
The critical step: do not reinstall the filter until it is fully dry. A damp filter placed back into the machine creates the perfect environment for mold and bacteria to grow. Depending on humidity in your home, drying can take several hours. Some people keep a second foam filter on hand so they can swap in a dry one while the other dries overnight.
When to Replace Each Filter
Replace foam filters every one to three months, even with regular cleaning. Over time, the foam loses its structure and stops trapping particles effectively. You’ll notice it looking thinner, discolored, or less springy. At that point, washing won’t restore it.
Disposable paper filters should be replaced on a similar schedule, roughly every month or when they look visibly gray or discolored. Hold a used one up next to a fresh one and the difference is usually obvious. A government review of major CPAP manufacturers (ResMed, Philips Respironics, Fisher & Paykel, and DeVilbiss) found that none of them gave a single fixed replacement timeline. Instead, each noted that replacement frequency depends on how often you use your machine, how you clean it, and the environment where you sleep.
That last factor matters more than most people realize.
Homes With Pets, Dust, or Smokers
If you have pets, live in a dusty area, or anyone in your household smokes, your filters are working harder every night. Pet dander and fur clog foam filters faster. Dust-heavy environments do the same. Tobacco smoke is especially demanding on the disposable paper filter, which is the only layer fine enough to catch those particles.
In these situations, check your foam filter twice a week instead of once, and wash it whenever it looks dirty. Replace disposable filters closer to the two-week mark rather than waiting a full month. During allergy season or in homes undergoing renovation, the same accelerated schedule applies. If you pull a filter out and it’s visibly gray or smells musty, it’s already overdue.
What Not to Use for Cleaning
Stick to mild soap and water. The FDA has specifically reminded consumers that no ozone gas or UV light devices have been authorized to clean, disinfect, or sanitize CPAP equipment. Ozone needs to reach concentrations above safe human exposure levels to actually kill bacteria, which creates its own health risk. One major ozone-based cleaner, SoClean, was subject to a voluntary recall.
Avoid bleach, rubbing alcohol, scented soaps, and antibacterial cleaners. These can leave chemical residues on the foam that get aerosolized by the machine’s airflow and inhaled directly into your lungs. Vinegar is sometimes suggested online, but manufacturers generally do not recommend it. Plain dish soap, free of dyes and perfumes, is the safest and most effective option.
Why Dirty Filters Matter for Your Health
A CPAP machine pushes air directly into your airway all night. Every particle that gets past a degraded or clogged filter goes straight into your lungs. Over time, bacteria and mold can colonize a dirty filter, and breathing in those organisms can trigger or worsen asthma, reactive airway disease, and other lung conditions. Harvard Health Publishing notes that the warm, moist environment inside CPAP equipment is especially hospitable to bacterial and mold growth.
A clogged filter also forces the machine to work harder to push air through, which can reduce the pressure reaching your airway. That means your sleep apnea treatment becomes less effective without any change to your machine’s settings. If you’ve noticed your therapy feeling weaker or your mouth feeling drier than usual, a dirty filter is one of the first things to check.
Quick Weekly Routine
- Remove both filters from the machine’s filter compartment.
- Inspect the disposable filter. If it’s gray or has been in use for a month or more, discard it and insert a fresh one.
- Wash the foam filter in warm water with a small amount of mild, unscented soap.
- Rinse thoroughly until the water runs clear and no soap remains.
- Blot with a clean towel and lay flat to air dry away from sunlight.
- Reinstall only when completely dry. If you use your machine nightly, wash the filter in the morning so it has all day to dry.
Keeping a few spare disposable filters and one backup foam filter on hand means you never have to skip a night of therapy while waiting for parts to dry or replacements to arrive. Most are inexpensive and available through your CPAP supplier, pharmacy, or online.