Air filtration systems that many had hoped would reduce sickness do not reduce the risk of viral infections, leading researchers at the UEA say.
At the height of the Covid pandemic, many organisation explored investing in "air cleaners" in hopes of making indoor social interactions safer.
However, a new study from virologists from the University of East Anglia's Norwich Medical School has found the devices are not effective in the real world.
The study assessed the effectiveness of technologies including air filtration, germicidal lights and ionises.
However, it found little evidence that the systems reduce the risk of infection.
Prof Paul Hunter, from the UEA, said: "Air cleaners are designed to filter pollutants or contaminants out of the air that passes through them.
"But air treatment technologies can be expensive - so it's reasonable to weigh up the benefits against the costs."
Dr Julii Brainard, the project's lead researcher, said: "In short, we found no strong evidence that air treatment technologies are likely to protect people in real-world settings.
"Our findings are disappointing - but it is vital that public health decision-makers have a full picture."
