Research shows that air filters don't stop you getting sick

Air filtration systems do not appear to reduce your risk of picking up viral infections, according to new research into technologies including air filtration, germicidal lights and ionisers. The work was led by the University of East Anglia (UEA) in collaboration with the University College London, the University of Essex, the Norfolk and Norwich University Hospital Trust, and the University of Surrey.

“Air cleaners are designed to filter pollutants or contaminants out of the air that passes through them,” said UEA’s Professor Paul Hunter.

“When the COVID pandemic hit, many large companies and governments — including the NHS, the British military, and New York City and regional German governments — investigated installing this type of technology in a bid to reduce airborne virus particles in buildings and small spaces.

“But air treatment technologies can be expensive. So it’s reasonable to weigh up the benefits against costs, and to understand the current capabilities of such technologies.”

The research team set out to study evidence about whether air-cleaning technologies make people safe from catching airborne respiratory or gastrointestinal infections. As noted by lead researcher Dr Julii Brainard: “The kinds of technologies that we considered included filtration, germicidal lights, ionisers and any other way of safely removing viruses or deactivating them in breathable air.”

The team analysed evidence about microbial infections or symptoms in people exposed or not to air treatment technologies in 32 studies, all conducted in real-world settings like schools or care homes (so far, none of the studies of air treatment started during the COVID era have been published). The results were published in the journal Preventative Medicine.

“In short,” Brainard said, “we found no strong evidence that air treatment technologies are likely to protect people in real-world settings.

“There is a lot of existing evidence that environmental and surface contamination can be reduced by several air treatment strategies, especially germicidal lights and high efficiency particulate air filtration (HEPA). But the combined evidence was that these technologies don’t stop or reduce illness.

“There was some weak evidence that the air treatment methods reduced likelihood of infection, but this evidence seems biased and imbalanced.

“We strongly suspect that there were some relevant studies with very minor or no effect, but these were never published.”

Brainard acknowledged that the results were disappointing, but said it is vital that public health decision-makers have the full picture. She remains hopeful that those studies that were conducted during the pandemic will be published soon, which would enable a more informed judgement about the value of air treatment.

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