Air filters don’t stop you catching infectious respiratory diseases, landmark study indicates

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By Paul Hunter and Julii Brainard

There was an energetic push to install air-filtering devices in schools and care homes when the COVID pandemic struck. However, these devices had rarely been tested in real situations looking at infection outcomes in people.

Because there was no solid proof that these devices actually worked, researchers ran a trial testing whether air filters can prevent viral respiratory infections in care homes for the elderly. The filters used in the study – called Hepa (high-efficiency particulate air) filters – are designed to remove more than 99.9% of very small particles from the air, including, in theory, many viruses.

The UK trial, funded by the National Institute for Health and Care Research, included 91 care homes. Forty-seven were given Hepa filters for communal areas, and 44 were not. Researchers then tracked whether residents or staff developed respiratory infections, and whether staff needed time off sick.

The results showed that there was no difference in infection rates between homes with filters and homes without. There was also no difference in staff illnesses or absenteeism between homes with and without filters.