Expensive air-filtration systems are not effective in preventing respiratory or gastrointestinal infections, according to researchers at the University of East Anglia (UEA). A meta-analysis conducted by the UEA found little evidence to support the idea that air purifiers can make indoor air safe. The study, titled 'Effectiveness of filtering or decontaminating air to reduce or prevent respiratory infections: A systematic review', analyzed evidence from 32 studies conducted in real-world settings. The researchers concluded that air treatment technologies do not stop or reduce illness.