Want to avoid getting sick? Our data reveals this air purifier works best

Key points to remember:

• Health experts recommend using air purifiers to help prevent illness during cold and flu season because viruses like influenza and SARS-CoV-2 are carried in respiratory aerosols.
• Health experts recommend running your air purifier continuously at low speed to minimize the risk of illness. If someone is actively ill, prioritize high fan speed.
• Our proprietary laboratory data reveals that the Shark HP232 achieved better particle removal results at a low fan setting, while the Coway Airmega 400S performance is better at a high fan setting.
• Other important factors for disease prevention include an air purifier with a true HEPA filter and strategic placement of the device in your home.

As a wellness writer living in Southern California, I’ve primarily used my air purifiers during wildfire season. However, I’ve always wondered if these devices could also help prevent illness during cold and flu season.

According to exclusive data from CNET’s laboratory, the answer is yes. And health experts agree.

Pediatric allergist and clinical immunologist Dr. Zachary Rubin told CNET that viruses like influenza and SARS-CoV-2, a member of the coronavirus family, are carried in respiratory aerosols, which are particles that are exhaled when you breathe, cough, talk or sneeze. They are usually less than 5 μm in size, but many can be less than 1 μm and your air purifier should be able to remove them.

Primary and emergency care physician Dr. Steven Goldberg, chief medical officer of the HealthTrackRX Molecular Testing Laboratory, notes that an air purifier capable of removing particles as small as 0.3 μm is a particularly vital benchmark for viral aerosol removal, especially since manufacturers often rate purifying filters based on their effectiveness in removing particles of this size.

To test this, CNET Labs placed 12 popular air purifiers in a smoke chamber to measure their ability to filter five different particle sizes, fine and coarse, from the air. Two models have proven to be very successful thanks to their rapid results, making them essential devices for cold and flu season.

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The best air purifier to prevent illness, according to our tests

We tested all 12 air purifiers at low and high fan speeds to assess their effectiveness at removing fine particles. These are the models that have proven to be the most efficient.

At low fan speed

At a low fan setting, the Shark HP232 achieved the best results for removing fine particles, averaging 1 minute and 15 seconds. It also achieved the best results at this same speed for all particles with an average time of 1 minute and 20 seconds. This makes it our winner for “Best in Low Setting Particle Removal.”

Figure 1: The y-axis displays the 12 air purifiers we tested, and the x-axis displays the T90, or the time it took to remove 90% of particles, in the following format: [minutes].[seconds]. This is for low fan speed. Black bars represent fine particles measuring 2.5 μm and less, while red bars represent coarse particles measuring 10.0 μm and less.

Designed for spaces up to 1,200 square feet, the HP232 uses Shark’s Nanoseal anti-allergen filter with true HEPA, which the company says captures 99.98 percent of large, small, and micron particles between 0.1 and 0.2 microns. HEPA stands for “high-efficiency particulate air” and is a type of air filter used in air purifiers.

The Shark HP232 costs $330 full price, making it the seventh cheapest model we’ve tested. The most affordable option tested is Morento indoor air purifierpriced at $79, but it didn’t perform as well in our particle tests.

Second place for low-speed fine particle removal goes to Coway Airmega 400Swhich is the fourth most expensive unit at $565. THE BlueAir 311i came in third place, while the Oransi ModPlus came in fourth place. The BlueAir model is the fourth cheapest model at $160, while the Oransi is the third most expensive model at $640.

At high fan speed

At high fan speed, the Coway Airmega 400S was best at removing 90% of fine particles in 34 seconds on average. It also reigned supreme by eliminating all particles on average at high speed in 35 seconds. It won our “Best in High Setting Particle Removal” award.

Figure 2: The y-axis displays the 12 air purifiers we tested, and the x-axis displays the T90, or the time it took to remove 90% of particles, in the following format: [minutes].[seconds]. This is for high fan speed. Black bars represent fine particles measuring 2.5 μm and less, while red bars represent coarse particles measuring 10.0 μm and less.

Interestingly, the Shark HP232, our winner for low fan particle removal, placed seventh for fine particles at high fan speed with an average duration of 1 minute and 15 seconds. The Oransi Mod Plus is better placed in second place with 47 seconds. In third position, the BlueAir 311i and Levoit Core 400S tied at an average of 49 seconds for fine particles and 48 seconds for all particles. The $181 Levoit model, however, costs $21 more than the BlueAir 311i.

Which air purifier speed is best for preventing illness?

Based on our data, you may be wondering: For cold and flu seasonshould I go for an air purifier that works best at removing the finest particles at low or high speed? According to Rubin, continuous low-speed operation is best for prevent disease because “this keeps background aerosol concentrations low at all times”.

Goldberg echoes this, adding that many manufacturers’ user guides recommend a low-speed continuous mode for optimal performance.

“High speed bursts are only useful in addition to continued use – for example, immediately after someone coughs, sneezes or leaves the room – but they should not replace basic filtration,” says Rubin.

If someone is sick, you’ll want to prioritize cleaning speed at a medium or high setting. If these fan speeds are too high for sleepyou can switch to a low fan speed at night, allowing it to filter particles in the background. However, if you can tolerate it, Goldberg points out that a higher fan speed will provide higher airflow, which is more effective at quickly removing aerosols when someone in your home is sick.

“In bedrooms, quieter environments are acceptable as long as the device can still remove fine particles in about 5 minutes,” says Dr. Raj Dasgupta, Sleepopolis’ chief medical advisor, quadruple board certified in pulmonary, sleep, internal medicine, and critical care.

In other words, an air purifier that operates efficiently at low speed is ideal for cold and flu season. Our tests reveal that it is the Shark HP232. However, if someone is actively sick, you’ll want your device to purify effectively at high speeds, which is something the Coway Airmega 400S was best at in our testing.

“If someone is sick, combining a purifier on medium or high power and opening a window for 5 to 10 minutes significantly improves air quality,” says Rubin.

According to our tests, the most efficient air purifiers for eliminating fine particles on both low and high fan speeds are the Coway Airmega 400S, priced high-end at $565, ​​and the Oransi Mod Plus, which is more expensive at $640. A more affordable model that still ranks in the top four for both fan speeds is the BlueAir 311i, priced at $330.

How long does it take an air purifier to remove fine particles?

Although there is no universally accepted removal time frame for fine particles, Goldberg says rapid removal within minutes is most effective in preventing disease.

“A purifier should ideally remove 90% of fine particles within one to three minutes,” says Dasgupta. “Up to 5 minutes is still helpful in reducing exposure.”

For an air purifier to be considered effective at removing fine particles when a person is sick, Rubin provided the following criteria:

• Less than 3 minutes top: excellent
• 3 to 5 minutes: acceptable for most situations
• More than 8 to 10 minutes: too slow to significantly reduce risks in the event of active illness or gatherings

“If a unit takes about 10 minutes or more to remove 90 percent of fine particles, it probably won’t keep up with continued aerosol production when someone in the house is sick,” Rubin says.

Our tests found two air purifiers that took 10 minutes or more to remove 90% of 0.3-µm particles at low fan speed: the $519 model. Airdog Green Technology X5 Air Purifier and the $750 Dyson Formaldehyde TP09the second most expensive unit tested at just $10 less than the $760 RabbitAir A3.

At low speeds, the Dyson also struggled with all other particle sizes, lagging behind the other 11 models tested. On average, it took the Dyson 8 minutes and 26 seconds on low speed to remove 90% of fine particles. For all particles, the average duration was 7 minutes.

The Dyson Formaldehyde TP09 is specially designed to detect and destroy formaldehyde with a catalytic filter. The device uses an H13 HEPA filter with a removal efficiency of 99.95% for particles down to 0.1 microns per liter of air, as well as activated carbon filters that capture 99.97% of particles down to 0.3 microns, including allergens, bacteriaviruses, pollen and mold spores. Dyson purifiers also feature Air Multiplier technology, which can purify an entire room.

At high speed, the Airdog also took at least 10 minutes to remove 90% of 0.3 µm particles, but had no problems with other particle sizes. This air purifier uses TPA (Two-Pole Action) technology, which claims to “capture and destroy pollutants 20 times smaller than conventional air purifiers, all without using non-recyclable and environmentally harmful HEPA filters.” It says it can remove pollutants of at least 0.0146 microns.

CNET Senior Lab Engineer Gianmarco Chumbe explains why Dyson wasn’t as effective as other purifiers: “Our smoke chamber is designed as a torture test that pushes purifiers to remove a very dense concentration of particles in a confined space as quickly as possible. Dyson’s purifiers use an air multiplier and a projection-style airflow system optimized to circulate air over a greater volume.”

Due to Dyson’s specific system, it will not perform as expected in a smaller chamber like the one used for our testing. Chumbe emphasizes that this does not indicate a malfunction. “This simply reflects the behavior of this specific fan technology under our high-intensity, small-volume test conditions.”

Added “seed” features are something to be disdained

Air purifier brands advertise various additional features, such as special “germ” filters or UV-C germicidal bulbs, claiming they can reduce germs in the air. However, our tests reveal that what is most important for preventing disease is performance.

“The most important factors are airflow and a high-quality HEPA filter,” says Rubin. “Germ filters rarely provide measurable benefits. Integrated UV-C often uses weak bulbs with too short an exposure time for reliable neutralization. activate viruses, so this should not motivate a purchasing decision.

For HEPA filters, you will need true HEPA, which captures 99.97% of 0.3 μm particles. Activated charcoal can help reduce odors, but it does not eliminate viruses. You’ll want to avoid filters labeled HEPA-type, HEPA-type, or those claiming ionic or ozone-producing technologies.

As Airdog points out in its product description, HEPA filters are generally not reusable.

“Standard HEPA filters (H13/H14) are defined by their ability to remove at least 99.97% of particles larger than or equal to 0.3 µm and are the most established and widely recommended technology for removing viruses and fine airborne particles,” explains Goldberg.

Why your air purifier should appreciate life’s finest particles

In our CNET Labs tests, five different particle sizes were considered: 0.3 µm, 0.5 µm, 1.0 µm, 2.5 µm, 5.0 µm and 10.0 µm. The time it took 12 different air purifier models to remove 90 percent of these particles (represented by T90) released by a smoke bomb made of 50 percent potassium nitrate, 40 percent sugar, and 10 percent baking soda in a 96-cubic-foot chamber was measured with a particle counter at high and low fan speeds for each particle size.

Explaining why the T90 was the benchmark, Chumbe says: “The T90 is more useful than the T100. [100% of particles] because the last few percent of particle removal are slow, noisy and often dominated by measurement limits, making T90 a more reliable and practical measurement for comparing the particle filtration performance of air purifiers.

An average time was also calculated for all particles, with fine particles measuring 2.5 μm and less and coarse particles measuring 10 μm and less.

When asked which measure is most beneficial for cold and flu season, Rubin cites T90 for fine particles (2.5 μm and less). He adds that the performance of 0.3 μm and 0.5 μm is particularly relevant because these two sizes represent the most penetrating particle sizes (MPPS) for HEPA filtration.

Other Air Purifier Factors That Don’t Deserve to Be Cold

In addition to performance, there are additional air purifier features to consider.

Size

On the high and low fan settings, the best performing air purifiers were the large and medium sized air purifiers. According to Rubin, this is possible because larger models typically come with larger HEPA filters with more surface area to capture particles. They also have more powerful fans and higher clean air flow rates (also known as CADR).

“Even at low temperatures, [larger units] can move enough air to keep particle levels low, which your tests reflect,” he says.

Investment

Once you have your air purifier, make sure it is in the right location for optimal performance. This should be in a room where your household spends the most time, such as the bedroom or living room. Or, if someone is sick, place it where that person spends most of their time.

“In a bedroom, place it near the bed but not blowing directly on your face,” Rubin recommends.

For optimal air circulation, place the air purifier 3 to 6 feet from walls, avoiding corners and areas behind furniture. Goldberg does not recommend placing the air purifier near open windows or doors, as this could cause a short circuit and reduce its effectiveness.

Air quality indicators

Air quality indicator lights or automatic modes can be beneficial for people who don’t want to manually adjust their air purifier settings, but Rubin says they aren’t effective at preventing illness.

“These sensors are very effective at detecting larger particles like dust, cooking smoke or candle soot, so the purifier can automatically increase its power when indoor air becomes visibly or measurably dirtier,” says Rubin. “However, these sensors typically cannot detect the smallest virus-carrying respiratory aerosols, so the purifier may remain at a low level even when someone in the room exhales infectious particles.

When someone in the house is sick, it is more important to run the air purifier on medium or high speed, regardless of what the unit’s indicator may indicate. Dasgupta adds that during cold and flu season, continuous operation provides more reliable protection than relying on air quality sensors.

Our latest recommendations

Based on our testing and analysis from our health experts, we recommend the Shark HP232 to effectively remove fine particles continuously at low speed to prevent illness during cold and flu season. To achieve similar results at high speed, especially when you are sick, we recommend the Coway Airmega 400S.

“Don’t underestimate continued use,” Rubin concludes. “Even an average purifier can be very effective if it runs 24/7.”

The next time you’re trying to avoid illness, don’t just stock your medicine cabinet: make sure your air purifier is working to decontaminate the air you breathe. This way we can all take a deep, cleansing breath.