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Now is the time to buy an air purifier, before wildfires start

We take a look at how these air cleaning machines work and why you might want one in your home.

NASA's Terra satellite caught this view of the smoke from the 2018 Camp Fire across California.

Wildfires have unfortunately become a fact of life in the US during the summer, especially on the west coast. With a potentially historic drought looming, we could see more devastating wildfires this year and where there's fire, there is smoke. That smoke creates breathing hazards for millions of people, both those who live near the fires and people much farther, depending on how the wind blows. If smoke is creating a problem in your home, air purifiers are one way to combat the issue.

Read More: Best portable humidifiers for dry skin, sinus relief and sore throats

Sometimes referred to as air cleaners, air purifiers work to keep your home's climate healthy by removing polluting particles such as dust, pollen, pet dander, mold spores and smoke. These air cleaners are often packaged as portable units and fans. Here's how they can help you breathe easier.

What do they do? 

Portable air purifiers and air filters remove pollutants from the air. Indoor air pollutants fall into two main categories:

  • Particulate matter: This includes biological pollutants like mold spores, dust mites, bacteria, pet dander, viruses and smoke.
  • Gaseous pollutants: These are things like paints, varnishes, adhesives and pesticides. Especially dangerous gaseous pollutants are sometimes referred to as volatile organic compounds or VOCs.

Air purifiers work to filter these contaminants out of your air by filtering. Ideally, you'd take steps to avoid introducing these airborne particles in the first place, but in situations like wildfires, that's out of your control. 


The California Air Resource Board offers helpful information on wildfire effects and how it changes the particulate matter in your home. 


How do air purifiers work? 

Air purifiers remove these pollutants from the air using one of three common methods: filtration, electrostatic precipitation and ionizing. However, the EPA warns about the risk of ozone created by some electrostatic and ionizing air purifiers.

In fact, California law restricts the sale of ozone-producing air purifiers. The California Air Resources Board maintains a list of approved air cleaning devices. It also notes that using a CARB-certified air cleaner can "greatly reduce indoor particle levels to further reduce impacts from smoke."

Using filter-based air purifiers is widely considered healthier and more effective than ozone generators, so that's the method we'll focus on here. 

The most effective form of air filtration (and likely the one you've heard the most about) is a HEPA filter, which stands for high-efficiency particulate absorber. Models with filters pull in your home's air and move it through the filter with a circulating fan. 

When the air moves through each filter, any pollutants, particles or airborne allergens are caught in the filter. The clean air is then pushed back out into your space. HEPA filters do a better job here than a standard air filters because they can catch finer particles and purify the air more thoroughly. 

Colin McDonald/CNET

Once your home's air is feeling fresher, using preventive measures like not smoking indoors, vacuuming regularly, allowing fresh air in on occasion and keeping solid surfaces sanitized is a good way to combat indoor air issues. 

Buying tips

Air purifiers range from under $100 to well over $1,000, and the major difference is typically the amount of air (how many square feet) the device is able to effectively purify. Most models are designed to sit on the floor, but you can find tabletop models and even wall-mounted designs for air filtration.

When it comes to purchasing a portable air cleaner, the EPA suggests, "If you decide to purchase a portable air cleaner, choose one that is sized for the room in which you will use it." Read the product descriptions carefully to be sure you get an air filtration system big enough to fit your room, but remember that a larger model will likely also use more energy.

There are a few ways to be confident you're picking a good air purifier. You might see the abbreviation and value for CADR on an air purifier's packaging, which stands for "clean air delivery rate." That's a measure of how quickly the air purifier can deliver clean air. The higher the CADR, the more quickly the air pollutants are removed, though some manufacturers have suggested this lab testing method isn't an accurate simulation of how air filtration would work in an average home.

Air purifiers and HVAC filters are also measured by the minimum efficiency reporting value scale, where the lowest rating is 1 and the highest is 20. HEPA filters rate between 17 and 20. CARB recommends at least a 13 on the MERV scale for smoke mitigation. If you're in the market for an air purifier, look for a higher score on this scale if you're looking to solve serious asthma and allergy issues. 

We haven't tested air purifiers at CNET, but there are a host of well-reviewed and CARB-certified models available online. Here are a few notable options you can get via Amazon.


Dyson's desk fan air purifier updates you on your room's air quality in real time on its LCD screen display and uses a carbon filter and a glass HEPA filter that work together against microscopic pollutants and harmful gases. Its fan feature releases clean air back into the environment, with the option to project it toward you (say, for the warmer months) or away from you when it's cool enough already. And it can be controlled via remote or voice commands with an Amazon Alexa device.

In other words, this air purifier easily operates automatically, while keeping the user in the loop about what it's doing. "It detects practically immediately any kind of pollution (cigarette smoke, car exhaust gas, increased air dust, and so on...) and starts running, until the air is clean again," one Walmart reviewer explained. "The graphic display shows a lot of air-related features, like ambient air temperature, humidity and what kind of pollution it is 'fighting' against." Others praised it for its easy setup and fan feature, essentially making it a two-in-one product.


This air purifier -- which covers up to 167 square feet -- takes a three-pronged defense against poor quality: Its HEPA filter catches allergens and dust, its charcoal filter removes odors and its UV-C light acts as a disinfectant against bacteria, viruses and germs. 

One Amazon reviewer wrote about its particular effectiveness with pet dander: "We have two cats in our 4,000-sq-ft house. When my sister came from out of state, she asked if our cats ran away. She said our home had zero odor or scents, which is what I was going for." Another observed similar effects but also mentioned that the "high" and "medium" fan speeds are noisy to the point of distraction -- nevertheless, they considered it "a relatively cost-effective and efficient air purifier for a room under 200 square feet."

It should be noted that among the AC4825's many positive reviews are some alarming stories about models putting out high heat, smelling like burning plastic and even catching fire from the inside. According to one reviewer who started to experience these problems, the solution may be to keep a close eye on the filter and make sure it's changed regularly and not accumulating dust.

The largest air purifier on this list also has the largest coverage area by far. Using a combination carbon and HEPA filter, Coway's Airmega 400 can keep the air clean in rooms up to 1,560 square feet, making it an excellent choice for larger homes or rooms. "This filter is a large device and takes up a significant counter space, 15" wide x 15" long x 23" high. I have it working in a 1,600-square-foot room. It appears to work well without any effort and I have noticed a difference," one Amazon reviewer wrote, noting that the purifier's fan can get noisy if it's running at one of the higher speeds. 

Luckily, another Amazon reviewer observed that, while the fan undoubtedly gets pretty loud, the purifier's automatic smart mode only switches to the highest fan speed when it detects a major shift in air quality: "Using the default smart mode it automatically detects air quality and has four different air speeds. It only kicks on to the highest two setting when we've been cooking and only stays on those high settings for 3-5 minutes. The highest speed is loud and moves an absolutely insane amount of air. You'll need your TV 30% higher volume to hear it over this filter when it's cranked up all the way."


Honeywell recommends this model for extra-large rooms of up to 465 square feet. It comes with three air cleaning levels plus a Turbo Clean setting to remove pet dander, pollen, dust, mold and smoke. 


Coway's Mighty Air Purifier can accommodate rooms of up to 361 square feet. It runs at three speeds and includes LED indicator lights for air quality monitoring. There are also timers and auto-off functions if no pollution is detected after 30 minutes. 


With a streamlined design and an endless inventory of Instagram ads, the Molekule seems like a compelling air purifier for discerning shoppers. In addition to its good looks, Molekule uses its own patented filtering technology, Photo Electrochemical Oxidation (PECO), which claimed to catch and break down particles, then release nondangerous molecules back into the air. 

One study performed by the University of Minnesota demonstrated Molekule eliminating drastically more volatile organic compounds (VOCs) and mold than HEPA purifiers. But real-life tests on particulate matter demonstrate otherwise.

In Wirecutter's in-depth tests, Molekule was its worst pick. Wirecutter found that, "...on its auto setting, which is its medium setting, the Molekule reduced 0.3-micron particulates by (in the best case) only 26.4 percent over the course of half an hour. Compare that with the 87.6 percent reduction the Coway Mighty achieved on its medium setting." 

Consumer Reports also recommends against the air purifier. Both publishers tested the device and found it to to be in the bottom few of all tested air purifiers, suggesting other higher-performing options that cost much less.  

If you're still unsure, note that Molekule has a generous 60-day return policy. (All our other picks have a standard, 30-day policy.)

If smoke from wildfires is affecting your home, consider air filters or air purifiers to improve the indoor air quality until outdoor air quality improves. 

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Originally published in 2019. Updated for wildfire season and to add more context for Molekule.