Published: 21 November 2023
Research funded by the NIHR has found that air cleaning technologies designed to make social interactions safer in indoor spaces are not effective.
The research was funded by the NIHR Health Protection Research Unit (HPRU) in Emergency Preparedness and Response.
The researchers looked at technologies including:
- air filtration
- germicidal lights
- ionisers
They studied evidence about whether the technologies reduce the risk of catching airborne respiratory or gastrointestinal infections. The researchers found the technologies do not stop the spread of infections in buildings.
Prof Paul Hunter, from UEA’s Norwich Medical School, said: “Air cleaners are designed to filter pollutants or contaminants out of the air that passes through them.
“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 researchers analysed evidence about microbial infections or symptoms in people who had been exposed - or not - to air treatment technologies. All of the 32 studies analysed were conducted in real world settings such as schools or care homes. The researchers did not include any studies carried out during Covid because so far none of these have been published.
Lead researcher Dr Julii Brainard, also from UEA’s Norwich Medical School, said:
“In short, 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.
“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.”
The research was conducted by the University of East Anglia with collaborators:
University College London
the University of Essex
the Norfolk and Norwich University Hospital Trust
the University of Surrey
The research was funded by the NIHR HPRU in Emergency Preparedness and Response, which is a partnership between King’s College London, the UK Health Security Agency and the University of East Anglia.