Air purifiers are basically simple motors—little updated more than a fan and a filter. Yet a well-structured purifier can capture effectively all airborne allergens, such as pollen and mold spores, as well as bacteria, viruses, and smog.
We’ve tested more than 60 the best air purifiers(fintechzoom.com best air purifier) in the last nine years, and an extraordinary Coway Airmega AP-1512HH Mighty is our top pick between them. It’s powerful too much to clean a large area room, quiet enough to sleep near that, engineered to run for years, and low priced enough to set up several throughout a home. But it’s not the only best air purifier we’ve found, and if you like better the looks, price, or specifics of our other recommendations, be gurranteed that they are also top-notch performers.
Within 30 minutes, the Coway Airmega AP-1512HH Mighty lessen heavy smoke pollution in a New York City office by as much as 99.6% as compare to the performance of other top machines and has been compatible in multiple test spaces. We’ve hit this machine beyond its on-paper limits in numerous ways—including running its filters 24/7 for two years, twice as long as suggested—and it has never wavered or weakened. It offers great value on start and long-term costs, and its dense form, quiet operation, and display-light shutoff make it especially well suited to using it in a bedroom or living room.
The Coway Airmega 200M is effectively identical to Coway’s Airmega AP-1512HH Mighty in every important feature. They’re identical in noise and performance measure, their filters are replaceable, and their similar controls allow you to turn off the display lights. The 200M has a square grille in place of a round one, but that’s the only major physical difference. If you prefer the 200M’s looks or you find it at a better price, we suggest it.
The Winix 5500-2 is an extraordinary performer on particulates air pollution: It catch as much as 99.9% of the smoke in our test room in just 30 minutes on high pressure. We suggest the Coway Airmega AP-1512HH Mighty for its low energy usage, smaller visual footprint, and hand operated display-shutoff feature. The related 5300-2 and C535 (which is exclusive to the Winix store and Walmart) lack a few of the 5500-2’s features, but they carry out just as well and may be available at lower prices. We’ve had same strong results with every other Winix we’ve analyzed, including the AM80 and Wi-Fi–enabled AM90—not surprising given that the only meaningful differences between them are their looks.
The Blueair Blue Pure 311i Max delivers outstanding air purification performance, comparable to our other top picks for standard-sized spaces. It stands out for its ultra-quiet operation, excellent energy efficiency, and a convenient display shutoff feature. Improvements over its predecessor, the 311 Auto, include a re-engineered motor, a larger and less dense filter, and a more open outlet grille, all of which contribute to reduced electricity consumption and noise levels. The Blueair app adds convenience by allowing you to monitor air quality and control settings remotely. Its sleek design features a tweed-like, washable fabric cover available in several muted colors, making it an attractive addition to any room. However, one minor drawback is the recommended filter replacement every six to nine months, which results in higher annual costs compared to some similar models.
The Levoit Vital 200S performed on par with the Coway Airmega AP-1512HH Mighty in our performance tests, offering comparable energy efficiency, low noise levels, and a display shutoff feature that allows you to keep your preferred fan setting. During its first year of long-term testing in a New York City apartment, it has operated flawlessly.
The Blueair Blue Pure 211i Max is designed for large spaces up to 500 square feet and delivers exceptional performance, reducing smoke levels in our test room by over 99.9% on both its high and high-medium settings. Despite its power, it remains impressively energy-efficient and operates more quietly than expected. Features like a display shutoff make it ideal for light-sensitive users, especially during sleep, and a child lock ensures the controls stay secure. Its built-in air-quality sensor measures particulate pollution at 1, 2.5, and 10 microns (PM1, PM2.5, and PM10—corresponding to smoke, dust, and pollen). The companion app allows for remote monitoring and control of the device’s settings. While it’s priced accordingly for its capabilities, those with small to medium rooms can achieve excellent air purification for at least $100 less with other recommended models.
The compact Blueair Blue Pure 511 offers many of the features we love in other Blue Pure models, combined with impressive performance for its size and power. In our tests, it removed 96.9% of smoke particles in 30 minutes on high and 89.6% on medium. Despite its effectiveness, it remains extremely quiet, staying below 50 decibels even on its highest setting, making it ideal for TV viewing and sleeping. With an energy-efficient design that consumes just 3.5 watts on medium speed, it’s also cost-effective to run. Weighing under 4 pounds, it’s highly portable and fits easily on a shelf, desk, or floor. Plus, its display automatically turns off, ensuring it won’t distract you while you work or rest.
For reducing VOCs, we also recommend a specialized purifier below. However, this option has significant drawbacks and is best reserved for situations where opening a window isn’t feasible.
Why you should trust us
Since 2017, I have carried out thorough reporting on and hands-on testing of air purifiers in my New York City apartment and in Wirecutter’s New York and Los Angeles offices. I have consulted with manufacturers, engineers, researchers, and specialists. Additionally, I have personally used most of our recommendations, running them continuously for months—and occasionally years—in my apartment.
This experience has enabled me to collect objective insights into their long-term purification effectiveness and any mechanical wear. It has also allowed me to form well-informed opinions on aspects like ease of upkeep and use, the presence or absence of disruptive noises or lights, and overall aesthetic appeal—the so-called minor details that, if executed poorly, can transform what should be a nearly effortless appliance into a source of daily frustration.
Who this is for
If you suffer from allergies or are concerned about the air quality in your home, a HEPA air purifier can be an effective solution. These devices excel at one thing: removing fine particles from the air. They quickly and permanently capture the majority of common airborne allergens, including dust, pollen, mold, mildew, fungal spores, pet dander, and dust mites (and their waste). They are also highly effective at reducing smoke from wildfires, tobacco, and marijuana, as well as capturing airborne pathogens like bacteria and most, if not all, viruses—including the coronavirus. These machines are generally easy to use, but for a comprehensive guide, check out this piece on How to Set Up a best Air Purifier.
Keep in mind that once particulate matter settles on floors or surfaces, an air purifier cannot remove it. For allergens like pet hair and pollen on surfaces, you’ll need a vacuum cleaner or a dust mop. To eliminate viruses and bacteria on surfaces, cleaning with soap, detergent, or an all-purpose cleaner is usually sufficient.
How we picked
Air purifiers generally fall into three main categories: those designed for small spaces (such as kids’ bedrooms, dorm rooms, and offices), those meant for general living spaces (like enclosed living rooms and master bedrooms), and those intended for large areas (such as combined living/dining rooms or spaces with cathedral ceilings).
However, many manufacturers greatly exaggerate their machines’ capabilities. Some purifiers marketed for “living rooms” struggle to clear the air in even a walk-in closet.
To assess a purifier’s performance, we start by calculating its airflow potential. This begins with manufacturer-provided specifications, such as clean air delivery rate (CADR), to estimate the air changes per hour (ACH) it can provide in rooms of 150, 350, and 500 square feet (assuming an 8-foot ceiling height).
We consider four ACH the minimum requirement for a purifier to be effective in each room size. Based on years of real-world testing, we’ve found that four ACH ensures fast and thorough cleaning of heavily polluted air.
Most of the purifiers we recommend use true HEPA filters. In North America, “true HEPA” filters must capture at least 99.97% of airborne particles measuring 0.3 microns in diameter in a single pass. For comparison, human hair ranges from 20 to 180 microns wide. Interestingly, 0.3-micron particles are the hardest to filter using HEPA technology, so both larger and smaller particles are usually captured more efficiently.
The European equivalent to true HEPA, increasingly marketed in North America as “medical grade,” is H13. Its standards are nearly identical, requiring 99.95% single-pass capture of the most penetrating particle size (MPPS), which is typically close to 0.3 microns.
We also evaluate the value each purifier provides. Rather than imposing strict price limits for each room-size category, we compare cost with performance (especially ACH), projected maintenance and energy expenses over five years, user ratings, and the manufacturer’s track record for reliability and customer service.
Smart control capabilities are another factor we consider. Based on our testing, a high-quality purifier consistently creates and maintains clean air when left running continuously on a moderate setting. Therefore, we don’t require smart features in our picks. That said, many testers in our paid program have highlighted the benefits of app or voice control, particularly for people with mobility or dexterity challenges. Smart purifiers often provide real-time and trend data on indoor air quality and allow for scheduling, such as automatically performing a deep clean before you arrive home. While not essential for clean air, smart features can add significant convenience.
Lastly, we avoid ionizers and ozone. Many purifiers include an ionizer alongside a HEPA filter, but we recommend turning it off. The primary reason is that ionizers’ effectiveness remains uncertain. More importantly, ionizers can emit small amounts of ozone as a by-product, which is harmful to breathe. That said, any purifier we recommend with an ionizing option adheres to the strict California Air Resources Board limit of 0.05 parts per million of ozone production.
How we tested
The tools: Since 2016, we’ve conducted extensive real-world tests on air purifiers, using a TSI AeroTrak 9306—a professional-grade particle counter widely employed to certify air quality according to OSHA standards in workplaces like factories.
The venues: Our testing environments include homes and apartments. Since 2020, we’ve also been conducting tests in a 135-square-foot office at Wirecutter’s New York City headquarters.
The tests: Each test begins with a three-minute baseline measurement of ambient air quality. To elevate particulate levels, we burn five wooden matches and let the smoke circulate for two minutes. The purifiers are then run for the remaining 30 minutes.
Smoke particles fall into the challenging 0.3-micron size range, which is the HEPA test standard. A purifier that excels at capturing smoke particles will perform even better on larger particles like dust and pollen—and paradoxically, on smaller particles like bacteria and viruses. For more details, refer to How HEPA Filters Work.
During the tests, we position the purifiers at the center of the room, which is also the ideal placement in your own space. The particle counter is placed in the room’s farthest corner to ensure an accurate measurement of whole-room purification. The counter takes continuous readings, with particle counts totaled in one-minute intervals.We test each purifier at least twice. During a 35-minute test, we run the machine on its highest setting, which is typically noisy. In a separate test, we use the highest setting that keeps noise levels below 50 decibels—roughly the upper limit for tolerable sound during conversations, TV watching, or sleeping.
We normalize the test data. To ensure fair comparisons, we adjust each purifier’s data so its peak reading of 0.3-micron particles reflects the maximum particulate load it encountered. We then describe performance as the maximum reduction of particulates relative to that load. This method provides the most accurate apples-to-apples comparison, avoiding inconsistencies caused by absolute particle concentrations, which can vary between tests even in controlled lab settings.
We test both new and old machines. When retesting our current picks, we take four measurements—two with old filters and two with new ones—to determine how performance changes over time, if at all.
We also make subjective evaluations. Beyond raw performance, we assess how easy it is to live with these purifiers in real-life settings like bedrooms, living rooms, or offices. We measure noise levels, calculate long-term costs for energy and filter replacements, and evaluate ease of use and maintenance. We also consider factors such as distracting lights (which can interfere with sleep), the simplicity of controls, physical size, and overall aesthetics.
And we live with them. To understand their durability and long-term usability, we station our picks in various homes—sometimes for years—observing how they perform in different environments, withstand wear and tear from rowdy kids or other potential damage, and whether any new strengths or annoyances emerge over time.
Our pick: Coway Airmega AP-1512HH Mighty
After more than 20 rounds of testing, involving over 50 different air purifiers, and years of living with our top picks at home, the Coway Airmega AP-1512HH Mighty remains our top recommendation for most people. It has held this position since 2015 for good reasons.
Outstanding performance: Through repeated testing and re-testing, the Coway Mighty consistently ranks as one of the best-performing purifiers we’ve evaluated. On its high setting, it achieves an average of over 99% smoke removal in 30 minutes. Even on medium, it averages 88%. This performance persists throughout the lifespan of its HEPA filter, which requires annual replacement. We’ve run test units 24/7 for at least a year—sometimes for two—and then retested them with old filters, comparing results against new ones. In every instance, there was virtually no performance drop. (Interestingly, we’ve occasionally observed slight performance improvements, as HEPA filters can become more efficient at capturing particles as they clog, though this comes with a minor reduction in airflow.)
Built to last: Our first test unit ran continuously for two years and still performed like new before being replaced by a newer version. The second unit operated for four years without issues before being retired due to another design update. The third model ran at our office for over two years during the pandemic, enduring a period when the office was closed and even a minor flood. Despite these conditions, the purifier continued to function flawlessly upon reopening.It’s virtually set-and-forget. The Mighty requires minimal setup and maintenance. Simply remove the plastic wrapping from the filters, place them back in the purifier, and it’s ready to use.
We recommend running it on the medium setting, which is quiet, energy-efficient, and highly effective. In our past tests, we found that, in a closed room, this purifier could reduce particulate levels to nearly zero within an hour and maintain that level indefinitely.
It’s quiet. Despite its powerful performance, the Mighty is impressively quiet. On medium—our recommended setting—it registers just 39 decibels from 6 feet away, producing a gentle, fan-like hum that’s easy to sleep or watch TV near. (One reason we suggest sticking to medium is that the auto mode can unexpectedly ramp up the fan to its highest and much louder speed, as is the case with all purifiers that have an auto function.)
It goes dark. The Mighty includes a feature we wish all purifiers had: the ability to completely turn off its display while keeping it running at the chosen fan speed. Most air purifiers have overly bright displays, especially their air-quality indicator lights, which can be a nuisance for light-sensitive sleepers. While many purifiers now offer a sleep mode that dims or turns off the display, the Mighty does this perfectly.
It’s durable. Staff members who are parents report that the Mighty has withstood toddlers pressing the control panel and older kids playing roughly around it. Senior editor Harry Sawyers noted that his children discovered it could blow balloons into the air and even inflate their T-shirts to mimic the Stay Puft Marshmallow Man, with no harm to the machine.
It performs well in air-quality emergencies, like wildfires. In 2017, we recreated wildfire-like conditions in our Los Angeles office to test purifiers. Using several incense sticks, we filled a room much larger than the Coway is designed for with dense smoke. Even so, the Mighty reduced pollution levels by 70% in less than an hour, performing as well as purifiers designed for extra-large spaces.
It’s cost-efficient. Operating costs for the Mighty are among the lowest we’ve found for a purifier of its capabilities. The HEPA filter only needs to be replaced annually, compared to six- or eight-month replacement cycles for many competitors. It’s also energy-efficient: On medium, it uses just 8.1 watts, consuming only 71 kilowatt-hours annually when run 24/7. To estimate electricity costs, you can check the latest rates for your state on the US Energy Information Administration’s website.
Flaws but not dealbreakers
Fan issues appear resolved. In early fall 2020, some users reported problems with an imbalanced fan that caused the unit to shake excessively and, in some cases, led to fan damage. When we reached out, Coway acknowledged the issue and stated they were working on improving the fan’s balancing mechanism. Based on customer reviews as of late 2022, this problem seems to have been addressed.
Filter odor concerns resolved. Around the same time, some users noted a plasticky smell coming from new replacement filters. In February 2021, Coway explained that the odor stemmed from the polymers used in the filter’s manufacturing process, likening it to the smell of new clothing.
The company added that it was considering incorporating an Air Blow process during production to minimize odors. Filters we purchased in February 2021 had a slight smell, but by 2022, new filters showed no noticeable odor. Recent reviews from 2023 mention only a faint smell that dissipates within a day or two.
Third-party filters perform well but may void the warranty. We tested replacement filters from Cabiclean and Durabasics and found no noticeable odor. Both performed nearly identically to Coway’s original filters in our smoke tests, making them a solid alternative. However, Coway has stated that using third-party filters could void warranty coverage if an issue arises.
The smart version works, but the app disappoints. The smart model of the Coway Airmega AP-1512HH Mighty, the AP-1512HHS, offers remote monitoring and control via an app. While functional, the app is basic and prone to bugs. Thorin Klosowski, Wirecutter’s former editor of privacy and security coverage, noted that the app had poor reviews, frequently crashed, and requested unnecessary permissions, including access to location and the camera, which raised privacy concerns.
Runner-up: Coway Airmega 200M
The Coway Airmega 200M is nearly identical to our top pick, the Coway Airmega AP-1512HH Mighty. Both are made by the same manufacturer, and their faceplates and filters are even interchangeable. The 200M boasts a slightly more powerful motor, which may explain its slightly better performance in our tests: on its highest setting for 30 minutes, it reduced particulates by 99.4% with new filters (compared to the Mighty’s 98.9%) and by 99.1% with old filters (versus the Mighty’s 98.9%). However, these differences are negligible and unlikely to be noticeable in daily use. If you prefer the 200M’s design or find it at a better price, it’s a solid alternative.
The 200M includes the same display-shutoff feature as the Mighty, which is especially valuable for bedroom use as it eliminates the bright air-quality indicator light. Aesthetically, the 200M features a square grille instead of the Mighty’s round aperture. It is available in both black and white versions, just like the Mighty.
Also great: Winix 5500-2
The reliable Winix 5500-2 matched the performance of the Coway Mighty in our testing. Both purifiers are equally quiet, and the 5500-2 often comes at a slightly lower price. However, it’s not our top pick for a few reasons: it’s bulkier and less visually appealing to many, it lacks a display-shutoff feature (except on the lowest fan setting), and it consumes more electricity, leading to marginally higher operating costs. That said, the 5500-2 is an excellent purifier, and several Wirecutter staff members have used it happily for years.
All the Winix purifiers we’ve tested have delivered impressive results. If the 5500-2 isn’t available, the Winix 5300-2 offers identical performance but lacks the remote control included with the 5500-2. Similarly, the Winix C535—sold exclusively at Walmart and through Winix—often costs less than the 5500-2 and includes a two-year supply of filters. For a sleeker, more modern design, the AM80 and Wi-Fi-enabled AM90 are also strong performers.
Blueair Blue Pure 311i Max
The Blueair Blue Pure 311i Max is another outstanding air purifier, on par with our Coway picks in terms of performance. It’s incredibly energy-efficient, drawing only 30 watts on its highest setting (out of four), compared to the Coway Mighty’s 68 watts. In terms of performance, it’s exceptional, reducing smoke levels by 99.9% on high and 99.7% on medium-high. It’s also impressively quiet, never exceeding the 50-decibel threshold we consider acceptable for sleeping, talking, or watching TV nearby.On medium, low, and the ultra-low “nighttime” setting, it produces just 39 decibels or less, making it nearly inaudible.
Blueair explained in an interview that these features result from several engineering updates working together. The 311i Max’s motor and fan blade are more efficient than those in earlier models, with a gently flared shape and a slightly larger surface area compared to its predecessor, the 311 Auto (formerly a pick). In the 311i Max, a redesigned outlet grille provides more space for air to flow through. The filter itself uses the same technology as all Blueair purifiers, combining a non-HEPA filter (but still very efficient) with a system that gives an electrical charge to any particles that pass through, helping them stick to the filter through static cling the next time.
Additionally, the 311i Max has a new livability feature that was missing from earlier Blue Pure models: You can shut off the entire control panel display and the air-quality indicator while keeping the fan on the speed setting you prefer. Its new child-lock feature is also a great addition for households with young children.
The filters need to be replaced more frequently than those in the Mighty and many other models, with a replacement cycle of six to nine months, depending on usage (compared to the typical one-year cycle). The machine measures actual filter usage, not just the time elapsed since the last filter was installed, so if you don’t run it all the time, you’ll get more life out of the filters. However, over the long term, the more frequent filter replacements will likely lead to slightly higher running costs for the 311i Max.
Also great: Levoit Vital 200S
The Levoit Vital 200S is another excellent purifier and is similar to the Coway Mighty in both capability and livability. It excelled in our smoke tests, and it resembles the Mighty in energy usage and noise output (meaning it’s highly efficient and very quiet on its lower, everyday fan settings). There are four fan speeds to choose from (versus the Mighty’s three), so it offers a bit more flexibility. However, the medium-high setting approaches our 50-decibel limit on acceptable noise, so it’s not clear that this is a meaningful advantage.
Most important, the Vital 200S has a display shutoff that’s independent of the fan settings, so you can darken it at night while still keeping your air well cleaned. And our long-term test unit is performing without any issues, making us confident in its durability.
Budget pick: Blueair Blue Pure 511
For small spaces like bedrooms, dorm rooms, and offices, the Blueair Blue Pure 511 is an affordable, easy-to-use, and efficient air purifier. Its compact size and light weight allow it to sit on a desk, shelf, or the floor, and its minimalist design and automatic display-shutoff prevent it from being a visual distraction.
In our tests, the 511 reduced smoke levels by 96.9% in 30 minutes on its highest speed and by 89.6% on its medium speed. Even on its highest setting, it emitted only 48 decibels of fan-like white noise, which is quiet enough to sleep, work, or watch TV near.
On its medium and low settings, it’s nearly silent. Shortly after adjusting the fan speed, the entire display automatically turns off, so you won’t be bothered by lights while trying to sleep.
Like all purifiers in the Blue Pure series, the 511 is highly energy-efficient, using just 1.2, 3.5, and 13.6 watts on its low, medium, and high settings. The filter lasts about 6 months, with replacements costing around $20.
Weighing less than four pounds and standing at just 13.5 inches high by 7.75 inches wide, the 511 is easy to move and fits into nearly any space. For rooms under 180 square feet, it’s an excellent option. However, it is a basic machine, lacking smart functionality and an auto setting that adjusts the fan speed based on air quality. We plan to evaluate the upcoming 511i, which will include these features, later in 2024.
A good purifier for VOCs
If you’re specifically looking to address high levels of volatile organic compounds (VOCs), the Austin Air HealthMate HM400 is a top recommendation. Like other high-performing best air purifiers, it uses a HEPA filter to capture particulate pollutants. However, it also features a massive 15-pound adsorbent filter made of activated carbon and zeolites. This filter is highly effective at trapping gaseous pollutants such as formaldehyde, which makes it an excellent choice for homes or areas with significant VOC concerns. Unlike the small, short-lived VOC filters found in many purifiers, the HealthMate’s filter can last for several years.
However, in most parts of the country, simply opening windows periodically can help clear out VOCs, making it worth considering this free and easy option before investing in the HealthMate. The HealthMate HM400 does come with a few trade-offs, such as:
High upfront cost and replacement filter costs
Energy inefficiency, meaning it consumes more power than other options
Physical bulk, making it less suitable for smaller spaces
Noisy operation, which may be a concern for those who prefer quieter machines
While the HealthMate is excellent for VOCs, it’s essential to weigh these downsides against the simple, cost-effective option of ventilating your space regularly.
Whole-home purification options—if you have central HVAC
If you already have central HVAC, you can improve your indoor air quality by supplementing portable best air purifiers with whole-house filtration. Here are some methods and alternatives to explore:
- Upgrade to MERV 13 Filters
A straightforward solution is to swap your current filter with a MERV 13 filter in your HVAC system’s return registers. MERV (Minimum Efficiency Reporting Value) is a classification system used for HVAC filters. A MERV 13 filter is highly recommended for reducing airborne particulates like pollen, smoke, and PM2.5, and is commonly advised by professionals in the field. - Smart MERV 13 Filters
For a more advanced choice, you can replace your regular central filter with a MERV 13 smart filter that features a built-in sensor. This filter tracks your HVAC system’s performance and usage. When paired with a smart air quality monitor or thermostat, it can adjust fan speeds based on the detected air quality. For example, if particle levels rise (like from cooking or increased outdoor pollution), the monitor signals the thermostat to increase the fan speed until the air quality stabilizes. The Woosh smart air filter system is an excellent example of this approach. It provides:
Bluetooth-enabled sensors that track the filter’s condition and your HVAC’s performance.
Clever filter replacement system that minimizes waste by replacing only the filter material, thus extending the life of the frame.
Early alerts for HVAC issues by analyzing data like filter clogging and other operational metrics.
- Lennox PureAir System
If your HVAC system uses coarse fiberglass or low-MERV pleated filters, you might want to consider the Lennox PureAir system. This system adds a self-powered fan-and-filter unit to your HVAC, offering superior filtration with a MERV 16 filter (the highest efficiency below HEPA). The PureAir system captures a wide range of airborne particles, including:
Dust, pollen, and mold spores
Bacteria, viruses, and smoke
Household odors and VOCs (volatile organic compounds) such as paint fumes, adhesives, and cleaning chemicals.
Additionally, the PureAir system includes a UV-C sanitizing LED that neutralizes airborne pathogens, providing an extra level of protection. It’s especially beneficial for homes where HVAC systems were not originally built for high-efficiency filtration.
The Lennox PureAir system also comes in a smart version, the PureAir S, which syncs with smart thermostats and voice assistants, allowing remote monitoring and control of the filtration system.
Considerations:
Installation: Both the Woosh filter system and the Lennox PureAir require professional installation, especially the latter due to its more intricate setup.
Cost: The Lennox PureAir system entails a higher initial cost and more maintenance, but it provides superior filtration and additional features such as UV-C sanitizing and VOC removal.
Conclusion:
Both the Woosh smart air filter system and the Lennox PureAir offer excellent solutions to enhance air quality in homes with central HVAC systems. The Woosh system delivers a smart and adaptable approach, enabling remote air quality monitoring and HVAC adjustments, while the Lennox PureAir system provides top-tier filtration with MERV 16, effectively addressing both particulates and VOCs. However, if you’re simply looking to improve air quality without adding complexity, upgrading to a MERV 13 filter is a practical and cost-
effective choice.
How to set up, use, and maintain your air purifier
To maximize the effectiveness of an air purifier, it’s important to set it up properly, operate it correctly, and occasionally perform maintenance. Here’s a guide on what to do:
Unwrap the filters. Most air purifiers come with filters already installed, but they are often wrapped in plastic. Open your unit, remove the wrapping from the filters, and reinstall them. The HEPA filters should have an arrow or some other marking to indicate the correct alignment.
Position them correctly. Place your purifier at least 18 inches away from any walls or furniture, ideally in the center of the room you’re using it in.
One purifier per room is ideal. Air purifiers are most effective in a single, connected space. For example, if you want to purify the air in both the living room and a bedroom, it’s better to have one purifier for each room, or to move a single purifier from one room to another.
Larger models are fine. It’s preferable to have a purifier that’s too powerful rather than one that’s underpowered. Manufacturers generally base their room-size recommendations (and CADR ratings) on tests with the machines set to high. However, high speed can be too noisy when you’re watching TV or sleeping. Purifiers designed for larger areas can run on lower, quieter settings.
Keep it operating. Under normal conditions, we suggest running air purifiers continuously on their highest “quiet” setting, defined as 50 decibels (dBA) or less. This is usually the medium setting on three-speed purifiers, or the high-medium setting on four-speed models. During periods of poor air quality, such as a nearby wildfire, we advise running the purifier on high for about an hour periodically to thoroughly clean the air.
Shut doors and windows. A draft or open door can let in unfiltered air faster than the purifier can handle it. Normal foot traffic isn’t a problem; just be sure to close the door behind you.
Which settings should you run the best air purifier on?
In situations where air quality is poor, such as when a nearby wildfire affects your area, we suggest running the best air purifiers on high for an hour, followed by running them on a quieter or medium setting to create and maintain clean air in your home. We tested this method using the Coway Airmega AP-1512HH Mighty and the Airmega 400 over a three-hour period—one hour on high, followed by two hours on medium—after burning 15 wooden matches to introduce an initial heavy load of fine smoke particles.
When set to high, the AP-1512HH reduced the particulate concentration by 99.9% within the first hour. On the medium setting for the following two hours, the particulate load remained stable, fluctuating by no more than 0.1%. The Airmega 400 also reduced the particulate concentration by 99.9% during the first hour on high, with the particulate load varying by no more than 0.2% on medium after that. In these tests, the purifiers effectively managed normal ambient air after we artificially increased the smoke levels at the start.
How HEPA filters work
HEPA stands for “high-efficiency particulate air.” The filter technology is the result of an industrial need that became critical in the Atomic Age: high volumes of very clean air, vital for the production of microprocessors and other sensitive instruments. HEPA filtration is also fundamentally simple and cheap, which means it’s available to everyone today.
HEPA filtration is a physical process, but it’s not like what most people envision when they think of a filter: a net, or a colander, or maybe mosquito netting, where particles larger than the holes get caught and the rest passes through. Rather, in HEPA purifiers, a fan draws particles suspended in the air through a dense, felt-like filter that has billions of tiny gaps of varying size. Air passes through almost unimpeded—thus the “high-efficiency” in HEPA. But the maze-like web of fibers traps almost all of the particles, from relatively big material like pollen (10 microns or so) down to ultrafine, 0.01-micron (10 nanometers) stuff. That’s smaller than an individual virus.
The fibers in a HEPA filter capture airborne particulates in three basic ways (PDF).
Impaction: The largest of the particulates, about 0.5 micron and above, are captured via impaction: Unable to change their course due to momentum, the particulates simply slam into the fibers and stick to them.
Interception: Particles measuring less than 0.5 micron (but not too much less) are captured by interception: Their lower momentum allows them to flow around some fibers, but eventually they come close enough to touch one fiber on the way by, and again they stick.
Diffusion: Very fine particles measuring below 0.1 micron get bounced around randomly and are slowed by their interactions with atmospheric atoms and molecules. They eventually drift or get bounced into a filter fiber, whereupon (yet again) they stick in a process called diffusion.
Crucially, the hardest particles to capture are what you might call the Baby Bears: At 0.3 micron, they’re at the low limit of interception momentum and above the limit of diffusion—in other words, they’re “just right” to get through a HEPA filter. The solution is to make the filter dense enough that it has a sufficient amount of fibers to capture most of the 0.3-micron particles. According to the US HEPA standard, “most of them” means 99.97% of them in a single pass.