Best Air Purifiers for Cold & Flu Season: Lab Tests & Expert Advice

As winter descends and respiratory illnesses circulate, many are seeking ways to bolster their defenses. Beyond vaccinations and hygiene, a growing body of evidence suggests that air purification can play a significant role in reducing the risk of infection. Recent lab testing by CNET reveals that the Shark HP232 excels at particle removal on a low fan setting, even as the Coway Airmega 400S performs best at higher fan speeds. This data, combined with insights from medical professionals, offers a clearer picture of how to leverage air purification for improved health during cold and flu season.

How Air Purifiers Combat Airborne Illness

Viruses like influenza and SARS-CoV-2 aren’t simply spread through large droplets; they’re as well carried in respiratory aerosols – tiny particles expelled during breathing, coughing, talking and sneezing. These aerosols, often smaller than 5 μm (micrometers), can linger in the air, increasing the risk of transmission. Dr. Zachary Rubin, a pediatric allergist and clinical immunologist, explains that air purifiers help by removing these particles. The key, however, lies in the filter technology. An air purifier capable of removing 0.3 μm particles is considered a vital benchmark for viral aerosol removal, as manufacturers often rate filter efficiency based on this particle size. Dr. Steven Goldberg, chief medical officer at HealthTrackRX, emphasizes this point.

CNET Lab Testing: Low vs. High Fan Speeds

To determine which air purifiers are most effective, CNET Labs tested 12 popular models in a smoke chamber, measuring their ability to filter five different particle sizes. The results highlighted a clear distinction between performance at low and high fan speeds. The Shark HP232 demonstrated the fastest particle removal on a low setting, averaging 1 minute and 15 seconds to remove fine particles. The Coway Airmega 400S, priced at $749.00, excelled at high fan speeds, removing 90% of fine particles in just 34 seconds. This difference is crucial because, as experts suggest, continuous low-speed operation is generally preferable for minimizing illness risk.

The Importance of Consistent, Low-Level Filtration

Health experts recommend running air purifiers continuously on a low speed to maintain consistently low aerosol concentrations. This approach, according to Dr. Rubin, keeps background levels of potentially infectious particles down at all times. While a high fan speed is beneficial when someone is actively sick, it shouldn’t replace continuous, low-level filtration. Many manufacturers even recommend a continuous low-speed mode for optimal performance. The Shark HP232’s performance on low speed makes it a strong contender for year-round, preventative utilize.

Beyond HEPA: What to Glance for in an Air Purifier

A “true HEPA filter” is essential. These filters capture 99.97% of particles 0.3 μm in size. Activated carbon filters can help reduce odors, but they don’t eliminate viruses. Avoid filters labeled “HEPA-type” or those that produce ozone, as these are less effective and can even be harmful. The Coway Airmega 400S, for example, comes with two pre-filters and two Max2 HEPA filters. The Coway Airmega 400S also features smart capabilities, including Wi-Fi connectivity and real-time air quality monitoring via the Airmega mobile app.

Placement and Additional Considerations

Optimal air purifier placement is key. Position the unit in a room where you spend the most time, away from walls and furniture to allow for adequate airflow. Avoid placing it near open windows or doors, which can reduce its effectiveness. While features like germicidal UV-C light bulbs and “germ” filters are often marketed, experts suggest they offer limited benefit compared to a high-quality HEPA filter and consistent airflow. Dr. Rubin notes that UV-C bulbs often lack sufficient exposure time to reliably inactivate viruses.

What Happens Next: Maintaining Air Quality

The effectiveness of an air purifier isn’t solely about the initial purchase. Regular filter replacement is crucial. The Coway Airmega 400S filters are designed to last 6-12 months, while the Shark HP232 filter’s lifespan will vary depending on usage. Monitoring air quality indicators, if available, can provide a general sense of air cleanliness, but relying solely on these indicators isn’t sufficient when someone is sick. In those cases, prioritizing higher fan speeds is recommended, even if it means sacrificing some quietness. Continued research and development in air purification technology will likely lead to even more effective and efficient models in the future, but for now, a well-chosen air purifier, combined with other preventative measures, can be a valuable tool in protecting your health.