Home / Technology / Do air purifiers really work (and will they protect you from COVID-19)?

Do air purifiers really work (and will they protect you from COVID-19)?



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COVID-19 continues to put people around the world, and particularly in the United States, on edge. The thought of the proliferating virus in our own homes or schools – especially in poorly ventilated spaces – is enough to make most of us start to feel a little paranoid. What types of masks should we wear? Will hand washing really make a difference? Could air purifiers be another solution?

Well, to answer that last question, we spoke with a number of air quality experts. We asked if air purifiers can solve – or at least alleviate – some of our air quality problems, if we’re talking coronavirus virions floating in aerosol droplets around our home, or more mundane irritants like pollen or pollutants like smoke from wildfires and smog.

After test a dozen of the main air purifiers on the market, by discussing with specialists and reading dozens of studies on the subject, we arrived at some answers.

If I want an air purifier, how do I find the right one?

For those of you who already want an air purifier and want the basic recommendations, I have already written an in-depth article dealing with this exact issue. There are many air purifiers on the market, and some of them are really impressively effective considering their reasonable price.

For those who are still on the fence, read on.

Do Air Purifiers Really Work?

This is one of the most popular questions online, and it’s also a reminder of why careful reading and skepticism are such useful tools when researching products as a consumer. Developers of air purifiers are not allowed to advertise their devices as health products in the United States for several reasons – mainly because their benefits are not straightforward. Instead of claiming incredible health results, advertisements for purifiers usually focus on the number of harmful substances in the air and how effectively the devices filter them.


Molekule, which sells some of the best-looking purifiers on the market, was recently forced by the National Advertising Review Board to withdraw a slew of misleading claims it has made since 2017.

David Priest / CNET

To answer the question in the most basic terms: yes, air purifiers generally filter particles out of the air effectively – especially if they use a HEPA filter (more on those in the next section). But most of us already have a mechanism for filtering air efficiently: the respiratory system. As a microbiologist and vice president of scientific communications for the American Council on Science and Health, Dr. Alex Berezow pointed out in a recent blog post: “Living in the tiny air sacs of your lungs (called alveoli) are immune cells called macrophages. “big eaters” gobble up bacteria, viruses, fungi and other debris that ends up in the lungs. “

In short, air purifiers work, but unless you live in a particularly polluted environment or you or your children are immunosuppressed, you probably don’t need them.

Do they protect against COVID, wildfire smoke, or other seasonal pollutants?

HEPA, which stands for High Efficiency Particulate Air, is the standard that describes most air purifying filters currently sold in the United States. To meet the standard, a filter must remove 99.97% of particles in the air with a size of 0.3 microns (a particularly difficult size to filter). HEPA filters are generally more efficient with particles larger and smaller than this size. Pollen, smoke particles, and aerosol droplets that can transmit COVID can all be filtered out of the air with such a filter.

That said, don’t rely on air purifiers to protect you if you live with someone who is contagious. When I spoke on the phone with Dr Richard Shaughnessy, director of Tulsa Indoor Air Research University, he said transmission of COVID usually occurs through close contact with an infected person. . If you are sitting on a couch and chatting with an infected person, an air purifier across the room will not remove all the harmful particles they exhale before they have a chance to reach you.

An additional problem is the difference between capturing and killing viral particles. While HEPA filters will capture particles, other technologies, such as UV technology, will kill virions. Unfortunately, such technology is often accompanied by his own risks.


The Coway air purifier is one of the best on the market. It includes ion filtration technology, but has been certified by the California EPA to emit little or no ozone over time.

David Priest / CNET

I have heard of ozone from air purifiers. Should I be worried?

Ozone is a type of pollutant that a small set of air purifiers have been found to emit in the past. Before we dive into this, it helps to understand the basic types of air purifiers on the market. now.

The three filtration methods most used by air purifiers to clean the air are: HEPA devices remove particles by passing the air through a specially designed and standardized filter; activated carbon filters eliminate odors and gaseous pollutants by circulating the air over “absorbent supports”, which trap them; and finally, ionic purifiers produce ions which attach themselves to particles.

Ionic purifiers work in several ways. Some simply allow ionized particles to attach to surfaces around the house (thereby “removing” them from the air). Others have a plaque that collects these ionized particles and requires frequent cleaning. These are the devices that have in the past had problems with ozone production. Fortunately, standards have risen over the past few years and third-party companies are now testing ionic air purifiers to make sure they don’t release significant ozone into the home.

In general, I would avoid ionic air purifiers just because they aren’t the most effective for the price. If you really want one, make sure it has a certification from the Underwriters Laboratories or the California EPA that says it does not emit ozone.

Who would definitely benefit from an air purifier?

The research here is a bit complicated. Without going too far into the weeds, one of the clearest demographics that benefit from HEPA filter air purifiers is children with asthma. Dr Elizabeth Matsui, professor of population health and pediatrics at Dell Medical School at the University of Austin, has researched the use of air purifiers in homes for children with asthma and me. talked about the value of air purifiers in these households.


Even a great air purifier like the 411 from Blueair won’t do as much as cleaning and ventilating your home.

David Priest / CNET

Air purifiers, she warned, are not a substitute for what she calls “proximal source interventions.” For example, a HEPA air filter can reduce particulate matter in the home of a smoker and a child with asthma by 25% to 50%. But this is not the best solution: ideally, the person should quit smoking completely at home. A clean, well-ventilated environment – and of course proper medical care – is far more important than an expensive air filter.

And to be clear, while air purifiers can help alleviate the symptoms of childhood asthma, Dr. Matsui says, “There is no strong evidence that we can currently change a child’s environment. way who reduced rates asthma, whether by air purifiers or by any other means. “In other words, air purifiers are useful devices for children with asthma, but they won’t reduce a child’s chances of developing asthma in the first place.


With so many air purifiers on the market, finding the right one can seem overwhelming.

David Priest / CNET

If you have any other questions that I haven’t answered above, be sure to post them in the comments, and I’ll be happy to update the article with answers.

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