Airborne particles · 2026

Air purifiers and airborne viruses

Since 2020 there has been real interest in whether air purifiers reduce indoor transmission of airborne respiratory illness. The measured answer: filtration and high air-change rates reduce the concentration of airborne respiratory particles, which lowers exposure — but it is one layer, not a force field.

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What the evidence supports

Airborne respiratory particles are carried on aerosols in the size range MERV-13 captures well. Running high-airflow filtration in a shared room measurably lowers particle concentration — the principle behind the Corsi-Rosenthal box's rapid adoption in schools and offices during the pandemic.

Why airflow is decisive here

Reducing airborne exposure is about how many times per hour you clean the room's air. That makes clean-air delivery the key number — a high-airflow MERV-13 unit clearing a room many times an hour does more than a low-airflow HEPA unit clearing it slowly.

Honest limits

A purifier reduces airborne particle concentration; it does not eliminate close-range transmission or replace ventilation, vaccination or staying home when ill. Treat it as a strong, cheap additional layer — particularly in classrooms and offices.

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Frequently asked questions

Can an air purifier reduce virus transmission?

It reduces the concentration of airborne respiratory particles in a room, which lowers exposure. It is one effective layer alongside ventilation and other measures, not a complete solution.

What matters most for this?

Clean-air delivery — how many times per hour the room's air is filtered. High-airflow MERV-13 units excel here.

Is this why schools used Corsi-Rosenthal boxes?

Yes — cheap, high-airflow MERV-13 units were widely adopted in classrooms and offices to cut airborne particle concentration.