Air purifiers don’t stop you getting sick

The study, published in Preventive Medicine, concluded that technologies designed to make social interactions safer in indoor spaces, including air filtration, germicidal lights and ionisers, are not effective in the real world.

The researchers analysed evidence about microbial infections or symptoms in people who had or had not been exposed to air treatment technologies in 32 studies conducted in real world settings like schools or care homes. This did not include any studies of air treatment that began during the COVID-19 pandemic, none of which had been published when the research was conducted.

Despite looking at all the available evidence, the authors found little to support hopes that these technologies can make air safe from respiratory or gastrointestinal infections.

Medical student Isabel Swindells, an author of the study from UCL Medical School, said: "As global pandemics, such as COVID-19, permeate modern life, there is increasing interest in environmental interventions to protect against airborne diseases. Our findings don't indicate that current air filtration systems offer significant prevention in social, pragmatic settings. This may be disappointing, but it will allow us to direct efforts and resources toward interventions which could make a real difference."

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), had suggested that these technologies might reduce or prevent illness. But the combined findings indicated that they cannot.

Dr Julii Brainard, lead researcher of the study from UEA’s Norwich Medical School, said: “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.

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

“Our findings are disappointing – but it is vital that public health decision makers have a full picture. 

“Hopefully those studies that have been done during Covid will be published soon and we can make a more informed judgement about what the value of air treatment may have been during the pandemic.”

This research was led by the University of East Anglia with collaborators at UCL, the University of Essex, the Norfolk and Norwich University Hospital Trust, and the University of Surrey.

It was funded by the National Institute for Health and Care Research Health Protection Unit in Emergency Preparedness and Response, led by King’s College London and UEA in collaboration with the UK Health Security Agency.

Links 

• UCL Medical School
• UCL Faculty of Medical Sciences

Image

• Credit: Jomkwan on iStock.

Media contact 

Dr Matt Midgley

E: m.midgley [at] ucl.ac.uk