Why Your CPAP Filter Is Turning Black – And How To Fix It

Air entering a CPAP machine carries airborne contaminants that can cause the filter to turn black over time. Soot stains from candles and mold build-up due to high relative humidity can also make the filter black.

CPAP machines deliver a continuous flow of pressurized air to help relieve respiratory disorders, especially sleep apnea. Since these patients are at higher risk of airborne allergies, CPAP devices have filters that remove contaminants before heating, humidifying, and pressurizing the air, making it safe to breathe.

This article explains why your CPAP filter is turning black and how it impacts the machine. We then discuss how you can clean and maintain the air filter to improve its efficiency.

  • The reusable, disposable and bacteria filters on a CPAP machine can turn black over time.
  • A saturated filter, soot stains or mold build-ups can make a CPAP air filter black.
  • Regular maintenance, using an air purifier, and avoiding placing candles or heating devices near CPAP machines can prevent the air filters from turning black.
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Types of CPAP Air Filters

CPAP therapy is most commonly used for sleep apnea patients, which is a respiratory disorder in which the uvula and tongue relax, falling back against the soft palate.

CPAP or Continuous Positive Airway Pressure machines have a powerful motor that draws in surrounding air and pressurizes it.

This air first encounters air filters that trap the majority of its pollutants. The filtered air is then heated (as warm air tends to retain more moisture) and humidified before being transmitted to you via a tube and mask.

While the continuous pressure keeps the muscles from relaxing, the supply of warm, humid, and filtered air helps you breathe easily.

We know that air contains a variety of contaminants, including dust, debris, pollen, mold spores, several microbes, gases, and volatile organic compounds (VOCs). These are harmful and can cause a series of serious health complications ranging from mild respiratory distress and infections to heart diseases and lung cancer.

CPAP machines usually have the following filters to remove airborne allergens, toxins, and irritants:

  • Reusable Filter: These are foam filters that can be reused after a thorough wash. They are also known as pollen filters because the filtration media is optimized to capture particulate matter like dust, pollen, and pet hair.
  • Disposable Filter: These are electrostatically charged filters made of paper-like material. The electrostatic charge implies high-energy positive and negative ions that create static electricity in the surrounding area. This helps attract and trap airborne particulate matter like dust, debris, pollen, some allergens, and mold spores.
  • Bacteria Filter: Some high-end CPAP machines have a bacteria filter (usually a HEPA filter). It has microscopic pores that can trap pollutants measuring up to 0.3 microns and are best for filtering out microbes like mold, bacteria, and viruses.

For immunocompromised individuals or anyone with impaired respiratory functions, using a CPAP system with bacterial filters is essential.

Reasons Why Your CPAP Filter Might Be Black

Here’s why your CPAP filter might be black (keep reading for the solutions to each problem):

1. Clogging Due To Dirt

CPAP air filters have pores that trap pollutants. These pores have a specific capacity, beyond which they become saturated and cannot filter any more contaminants.

This generally happens when the CPAP is not cleaned or maintained regularly enough, and/or when the indoor air quality is poor.

2. Soot Stains

If your air filter turns black overnight, it is probably happening because of soot. Soot is a black, powdery byproduct of incomplete combustion and mainly consists of amorphous (structureless) carbon.

Lighting a candle or using a gas heater around the CPAP device can allow the soot produced during heating to build up in the filter.

You can confirm whether or not your candle, furnace, or other heating equipment/appliances are producing soot by looking for it on the floor nearby, and furniture as well.

Other than that, air conditioners, air purifiers, the furnace, and any other appliances with filters in the close vicinity will have black filters.

3. Mold

Mold is a pathogen that grows in colonies which can have a black, flaky appearance (depending on the type of mold).

It exists in the air as spores, which remain dormant until provided with adequate humidity (above 55% relative humidity). Therefore, if you live in a warm, humid climate, mold build-up is quite possibly why your CPAP filter is turning black.

How To Prevent The CPAP Air Filter From Turning Black

Here’s how you can prevent air filters from turning black:

1. Adequate Maintenance

Regular cleaning and general maintenance in-line with the instructions in your user manual is the best way to keep CPAP air filters working efficiently for a long time.

  • Remove the foam and paper filter and lightly tap it against a solid surface to remove dust from the pores.
  • If the filter appears severely clogged, rinse it with running water, and then leave it in for 10 to 15 minutes in a cleaning solution (1.25 ounce of dry powder in 1-gallon water).
  • Afterward, rinse the detergent off, and install the filter back in the machine once it’s fully dry.

Bacteria filters are generally non-washable and should just be replaced every four weeks. It is also crucial to change the foam and plastic filters after four weeks and six months, respectively. Note that this is a general optimal time span, and you might need to replace the filters sooner if the old ones are swollen or too dirty.

2. Avoiding Candles and Heating Appliances Around The Machine

As we said, soot can cause CPAP filters to stain black. To prevent this problem, it is better to avoid using candles, gas heaters, and other appliances that use combustion, around the CPAP system.

For the same reason, the room with a CPAP machine should also be a non-smoking zone.

This is also crucial as exhaust fumes from combustion can severely damage your lungs.

3. Air Purifiers To Improve Indoor AQI

Air purifiers are appliances that have a detailed filtration system, well-equipped to remove airborne contaminants from the room, thus improving the air quality.

High-end units with True HEPA, activated charcoal filters, UV bulbs, and electrostatic filters offer all-around protection against all types of pollutants, ranging from dust, debris, pollen, and microbes, to VOCs and poisonous gases.

Running an air purifier will reduce the load on CPAP filters (which are comparatively less effective), thus allowing them to last longer.

What Happens When Your CPAP Filter Is Black

A black CPAP filter indicates saturation of the filter pores. This not only impacts the efficiency of filtration but also obstructs the airflow, which directly, negatively affects CPAP therapy, and sleep quality.

Here’s how a clogged CPAP filter affects how a CPAP machine works:

Low Pressure

Like all medical conditions, sleep apnea has grades based on severity. Each patient requires varying air pressure from the machine depending on their condition. CPAP machines allow users to set their required pressure, and a steady supply of preset pressure is crucial for effective CPAP therapy.

Clogging in filters can obstruct the airflow. The dust and debris that escape the impaired filter collect in the system, resulting in overheating of the motor. The load on the motor reduces the efficiency of the entire system, and severely compromises CPAP therapy.

Plentiful Air has a detailed troubleshooting guide for CPAP machines that are losing pressure available here.

Water Leakage

The humidifier in the CPAP machine produces mist from the water, which is then added to the air to improve its moisture levels. Excessive dust and germ build-up in the humidifier bottle, as well as other areas of the machine, damages the material (usually polycarbonate), leading to cracks.

These cracks allow water and pressurized air to leak through the system.

Impaired Data Recording

CPAP machines record your sleep data by assessing the number of hours the machine is on your sleeping hours, apnea-hypopnea index, and leak rate of air through the mask.,

The data generates sleep scores, as well as a detailed history of interruption and leak rate, which are of crucial importance in your medical treatment.

The dust and debris build up in the oxygen tube, obstructing the airflow. Because the machine requires you to be connected to the CPAP system via a mask, it won’t record any data in case of complete severance of air supply, which can land you in trouble with insurance companies and the doctor.

Plentiful Air has more information on how to prevent problems with your CPAP mask – including making excessive noise – available here.

How Often Should You Change Filters On A CPAP Machine?

Generally, CPAP manufacturers recommend replacing paper filters every 2 to 4 weeks, foam filters every six months, and bacterial filters after four weeks of use. However, you should regularly inspect the filter for dust and germ buildup and change it sooner if need be.

What Happens If You Don’t Change Filters On CPAP?

When CPAP filters are not changed regularly (2 to 4 weeks for paper filters, six months for foam filters, and four weeks for bacterial filters), they become saturated and ineffective against airborne contaminants. This pollutes the pressurized air and obstructs the flow of incoming air.

Can I Clean The Filters In My CPAP Machine?

The disposable paper filters and reusable foam filters in CPAP machines can be cleaned and washed with mild detergent to remove collected dust and debris. However, bacterial filters (HEPA media) should never be rinsed.

Can I Use CPAP Without A Filter?

Never use a CPAP machine without a filter. Using a CPAP machine without a filter poses a significant health risk with airborne contaminants entering the respiratory tract. The pollutants can also build up and clog any area of the machine, constricting the airflow and consequently damaging the motor and other components of the device.

Russell Singleton

Russell holds a Bachelor of Science (Environmental and Marine Geoscience) with Class I Honors. He is currently completing his doctorate in science and is passionate about all earth processes, especially isotope geochemistry and paleohydrology.

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