An air purifier is a wonderful tool to have in your home, whether you want to avoid pollutants in your air or aim to prevent disease. However, if you don’t maintain it properly, you are making a mistake that could put your health at risk.

“If the filter is not changed regularly, the collected pollutants can build up and clog the filter. This leaves more pollutants in the air, and a dirty filter can release the contaminants back into your home, making the air even dirtier than if you didn’t use an air purifier,” he said. Kari Coyle is Dris a pulmonologist and assistant professor of medicine at New York Medical College.

Still not convinced? I consulted with health experts to learn more about the consequences of not changing your air purifier filter, as well as how often to do so.

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How not changing your air purifier filter affects your health

The purpose of an air purifier filter is to trap impurities, preventing them from circulating in the air and entering your body. As Coyle mentioned, these pollutants accumulate over time and can clog your filter, reducing airflow and filtration efficiency. Not only does this leave more pollutants in the air, but the filter can even release particles that were previously collected back into the air, further reducing your air quality.

“It can have respiratory, cardiovascular or allergic health effects,” said dr. Lyndsey Darrowepidemiologist and professor of public health at the University of Nevada, Reno.

A dirty air purifier filter is also more susceptible to mold growth, Coyle says, and the air purifier can circulate mold spores throughout your home. “This can cause serious illnesses such as worsening allergies, asthma symptoms and other respiratory problems,” he explained. “A dirty filter can make an indoor air quality worse than it would be without a cleaner.”

In other words, by not changing the filter in your air purifier, you are creating the opposite effect. All that allergensviruses, bacteriapollen and mold spores that you want your air purifier to remove can be pushed back into your air, where you can breathe it in and get sick.

Energy use and cost implications

Aside from the health-related effects of not changing your air purifier filter regularly, Darrow explains that a clogged filter will also require more energy to get air through, thus increasing energy use and costs. Over time, this can shorten the lifespan of your air purifier by destroying the motor or fan, which will require you to buy a new device and spend more money.

“Continued strain on the motor can result in the need for repair or replacement of the unit, which is more expensive than changing filters regularly,” Coyle points out.

The best filter for an air purifier

The gold-standard filter recommended by most pulmonary and allergy specialists is the HEPA filter. “This is because it removes most contaminants from the air down to the microscopic level,” Coyle said. “This includes removing dust, pollen, mold spores, dust mites, pet dander and other allergens, as well as most bacteria and viruses.”

Be aware that a HEPA-type or HEPA-like filter is not the same as a true HEPA filter.

The US Environmental Protection Agency states that HEPA filters are usually removed at least 99.97% of the particles in the air which measure 0.3 microns (µm) in size. This is especially beneficial because, according to pediatric allergist and clinical immunologist Dr. Zachary Rubin, who consulted for the CNET lab exclusively on best air purifier for cold and flu seasonviruses such as influenza and coronavirus are carried in respiratory aerosols that are usually less than 5 μm in size, and many are less than 1 μm.

While the HEPA filter removes many particles, chemical fumes, cigarette smoke and odors are not among them. That’s why Coyle recommends buying a HEPA filter with an activated carbon filter, which removes these environmental pollutants. For removing volatile organic compounds, gases emitted by products such as paint, cleaning supplies and furniture, the EPA advises using a thick activated carbon filter.

There’s also a pre-filter, which Coyle describes as another layer of respiratory protection. This removes large particles, such as lint, hair and dust clumps, preventing them from entering your HEPA filter and extending its life.

“If you’re concerned about airborne allergens, mold or fire smoke particles, having a HEPA filter is important,” says Darrow. “If you’re more concerned about gases (including volatile organic compounds) or odors, an activated carbon filter should be more effective for that purpose.”

There are filterless air purifiers known as ionizers that claim to work by charging airborne particles, causing them to fall out of the air or stick to other surfaces. However, Darrow says these devices produce ozone, a gaseous pollutant that is well-established as a respiratory irritant. That’s why HEPA and activated carbon filters are safer.

Before buying a filter for your air purifier, make sure it’s what the manufacturer recommends, because you want the right product for your specific model and room size.

How often should you change the air purifier filter?

Since there is no universally accepted recommendation for when to replace your air purifier’s filter, you should consult the manufacturer’s guide for your specific device. However, Darrow says it also depends on how polluted your air is and how often you use your air purifier.

“For example, if the manufacturer’s recommended replacement frequency for a HEPA filter is every 6 months, it should be changed more often if used in wildfire events or in homes with large allergens such as mold or pet dander,” said Darrow.

In general, it is recommended to replace your air purifier filter every three to six months, depending on the type of filter, usage and air quality. Coyle provides the following guidance:

• Main HEPA filter: Every six to 12 months.
• Carbon filters: Every three to six months, or when the odor returns.
• Pre-filter: Every one to three months.

But again, factors such as use, smoke, high pollution, allergies or pets may require you to change the filter of your air purifier regularly. That’s why you want to look for signs — such as decreased airflow, increased allergies, more dust in your home or lingering odors — that your filter needs to be changed.

Can you wash an air purifier filter instead of replacing it?

Most HEPA and carbon filters are disposable, and if you wash them, they can become damaged and ineffective — especially when it comes to capturing the finer particles of air pollutants like bacteria and allergens. If not completely dried before reinstalling it, the filter can also become a breeding ground for mold.

“Always check your manufacturer’s manual to determine if your specific filter is washable, as cleaning non-washable types can harm the unit’s performance and air quality,” Coyle emphasizes.

The bottom line

Before you turn on your air purifier, consult the manufacturer’s instructions to ensure that your filter is changed correctly and on time. Also note that if you have pets, live in an area with high pollution or experience wildfires, you may need to change the filter more often. And finally, be on the lookout for reduced performance from your air purifier, which may indicate that the filter needs to be changed.

The role of your air purifier is to clean the air you breathe in the name of your health. Not changing your filter can have the opposite effect. So, while a new air purifier filter every couple of months may be money you don’t want to spend, clean air and a clean bill of health are priceless.