Exclusive Lab Data: The Best Air Purifiers for Cold and Flu Season Revealed

As cold and flu season approaches, many are wondering if air purifiers can help prevent illness. Our exclusive lab testing, combined with expert medical insights, reveals the truth about these devices and which models truly excel at removing the fine particles that carry viruses.

The Science Behind Air Purification and Illness Prevention

According to Dr. Zachary Rubin, pediatric allergist and clinical immunologist, viruses like influenza and SARS-CoV-2 travel in respiratory aerosols—tiny particles exhaled when breathing, coughing, talking, or sneezing. These particles are typically under 5 micrometers in size, with many smaller than 1 micrometer.

Dr. Steven Goldberg, chief medical officer at HealthTrackRX, emphasizes that air purifiers capable of removing 0.3-micrometer particles are particularly vital for viral aerosol removal. This size represents the most penetrating particle size (MPPS) for HEPA filtration, making it a crucial benchmark for manufacturers.

Our Exclusive Testing Methodology

CNET Labs conducted rigorous testing on 12 popular air purifiers using a smoke chamber designed to simulate real-world conditions. We measured how quickly each model could remove five different particle sizes—both fine and coarse—using a particle counter. Testing was conducted at both low and high fan speeds to provide comprehensive performance data.

The Winners: Best Air Purifiers for Cold and Flu Season

Best at Particle Removal on Low Setting: Shark HP232

The Shark HP232 emerged as our top performer for continuous, low-speed operation—the recommended setting for illness prevention. This model removed 90% of fine particles in an impressive average of 1 minute and 15 seconds on low speed.

Key Features:

• True HEPA Anti-Allergen Nanoseal filter capturing 99.98% of particles from 0.1 to 0.2 microns
• Coverage area up to 1,200 square feet
• Priced at $330 (seventh cheapest in our test)

Dr. Rubin recommends continuous low-speed operation because “it keeps background aerosol concentrations low at all times,” making the Shark HP232 ideal for this purpose.

Best at Particle Removal on High Setting: Coway Airmega 400S

When someone is actively sick, higher fan speeds become crucial. The Coway Airmega 400S excelled in this category, removing 90% of fine particles in just 34 seconds on high speed.

Key Features:

• True HEPA filter with activated carbon
• Coverage area up to 1,560 square feet
• Priced at $565 (fourth most expensive in our test)

Expert Recommendations for Cold and Flu Season

Based on our testing and medical expert analysis, here are the key recommendations:

For prevention: Run your air purifier continuously on low speed. This keeps background aerosol concentrations consistently low, reducing the overall viral load in your indoor air.

When someone is sick: Switch to medium or high speed. Dr. Rubin notes that “high-speed bursts are only useful in addition to continuous use—for example, immediately after someone coughs, sneezes, or leaves the room.”

Ideal removal times: Dr. Raj Dasgupta, chief medical advisor for Sleepopolis, suggests that purifiers should ideally remove 90% of fine particles within 1-3 minutes, with up to 5 minutes still being helpful.

Other Top Performers

Our testing revealed several other models worth considering:

• Oransi Mod Plus: Ranked in the top four for both low and high-speed performance, though priced at $640
• BlueAir 311i: A more affordable option at $330 that still performed well across both speeds
• Levoit Core 400S: Tied for third place on high speed at $181

What About Those “Germ-Killing” Features?

Many air purifiers advertise additional features like UV-C light or special “germ” filters. However, our experts agree these features are largely unnecessary for illness prevention.

“The most important factors are airflow and a high-quality HEPA filter,” says Dr. Rubin. “Built-in UV-C often uses weak bulbs with too-short exposure time to reliably inactivate viruses, so it shouldn’t drive a purchasing decision.”

Proper Placement and Usage

To maximize your air purifier’s effectiveness:

• Place it in rooms where your household spends the most time
• Position 3-6 feet away from walls and avoid corners
• Keep away from open windows or doors
• In bedrooms, place near the bed but not blowing directly on your face
• For sick individuals, position the purifier in their primary space

Final Thoughts

Our comprehensive testing reveals that the Shark HP232 and Coway Airmega 400S represent the best options for cold and flu season, depending on your specific needs. The Shark excels at continuous, low-speed operation for prevention, while the Coway Airmega performs exceptionally when rapid particle removal is needed.

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

This cold and flu season, consider adding an air purifier to your wellness toolkit—not as a replacement for other preventive measures, but as a valuable complement to handwashing, vaccination, and other health practices.

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