To Avoid Getting Sick, Our Lab Data Shows You Need This Air Purifier Model
Can Your Air Purifier Actually Prevent Illness? Our Exclusive Lab Tests Reveal the Top Performers
As cold and flu season descends, many are turning to air purifiers as a line of defense against airborne viruses. But can a device designed to capture dust and pollen really stop you from getting sick? According to exclusive testing from CNET Labs and insights from leading health experts, the answer is a resounding yes-provided you choose the right model and use it correctly.
Our rigorous lab analysis of 12 popular air purifiers reveals that two models stand out for their ability to rapidly remove viral aerosols, with the Shark HP232 excelling at low fan speeds and the Coway Airmega 400S dominating on high. These findings offer a data-driven roadmap for staying healthy indoors this season.
The Science of Viral Capture: Why Air Purifiers Work
Viruses like influenza and SARS-CoV-2, the pathogen behind COVID-19, don't float freely in the air. Instead, they hitch a ride on respiratory aerosols-tiny particles exhaled when you breathe, cough, talk, or sneeze. These aerosols are typically under 5 micrometers (μm) in size, with many smaller than 1 μm. An effective air purifier must be able to capture particles in this microscopic range.
Dr. Zachary Rubin, a pediatric allergist and clinical immunologist, confirms that "air purifiers can remove virus-laden aerosols from indoor air, reducing the risk of transmission." Dr. Steven Goldberg, chief medical officer at HealthTrackRX and a primary care physician, emphasizes that a purifier's ability to filter 0.3 μm particles is a critical benchmark, as this is the standard size manufacturers use to rate HEPA filters.
"True HEPA filters are designed to capture 99.97% of particles as small as 0.3 μm," says Goldberg. "This makes them highly effective for viral aerosol removal, especially when paired with continuous operation."
Our Lab Test: How We Identified the Best Performers
To separate marketing hype from real-world performance, CNET Labs placed 12 leading air purifier models in a controlled smoke chamber. We measured each unit's ability to filter five distinct particle sizes-ranging from fine to coarse-at both low and high fan speeds. The metric: how quickly each purifier could reduce particle concentration to a safe level.
The results were striking. While many models performed adequately, two emerged as clear winners, making them essential tools for cold and flu season.
Low Fan Speed Winner: Shark HP232
For those who prefer a quieter, energy-efficient operation, the Shark HP232 is the undisputed champion. On its low fan setting, it removed fine particles in an average of just 1 minute and 15 seconds-the fastest of any model tested. Across all particle sizes, it averaged 1 minute and 20 seconds, earning it the title of "Best at Particle Removal on Low Setting."
This is particularly valuable for health experts' top recommendation: running your purifier continuously at low speed to minimize illness risk. The Shark HP232 proves you don't need to blast your unit to get protection.
High Fan Speed Winner: Coway Airmega 400S
When someone in your household is actively sick, experts advise cranking up the fan speed. In this scenario, the Coway Airmega 400S took the crown. On high, it outperformed every other model in rapid particle removal, making it the go-to choice for acute situations.
"If you have a sick family member, prioritize high fan speed to quickly clear the room of viral aerosols," says Dr. Rubin. The Coway Airmega 400S delivers exactly that, combining speed with the reliability of a true HEPA filter.
Beyond the Lab: Practical Tips for Illness Prevention
Our test data is clear, but hardware alone isn't enough. Health experts stress three additional factors for maximizing protection:
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Choose a true HEPA filter: Not all "HEPA-type" filters meet the 99.97% standard. Look for explicit "true HEPA" certification to ensure viral-sized particle capture.
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Strategic placement matters: Position your purifier in the room where you spend the most time-ideally the bedroom or living area. Avoid corners or behind furniture, which can obstruct airflow.
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Continuous low-speed operation: Running your unit 24/7 at low speed maintains a baseline of clean air. Only switch to high speed when someone is symptomatic or during peak exposure times.
Dr. Goldberg adds, "Air purifiers are a powerful supplement to vaccination, hand hygiene, and mask-wearing, but they are not a standalone solution. Combine them with other precautions for the best defense."
The Bottom Line: Which Purifier Should You Buy?
Our exclusive lab data proves that air purifiers can indeed prevent illness by removing virus-carrying aerosols from indoor air. For most households, the Shark HP232 offers the best balance of quiet, continuous protection. If you need maximum power for sick-room scenarios, the Coway Airmega 400S is your top pick.
As someone who relies on my air purifier for allergens and wildfire smoke, I can attest to its year-round value. But this cold and flu season, the evidence is undeniable: the right purifier, used correctly, is a smart investment in your health.
Disclaimer: Prices and availability updated as of 2026-05-12. We may earn a commission when you purchase through our links, at no extra cost to you. This supports our continued testing and reviews.