Because COVID-19 usually spreads from the mouth or nose, the researchers used spray dye to visualize droplets spread when someone coughs or exhales with and without a shield. Researchers tested three options: a large breath shield (45×44 centimeters), a standard small shield (11×11 centimeters), and no breath shield.
Large breath shields offered the best protection, stopping droplets from spreading when coughing or breathing. Small shields did not provide adequate protection against droplet spread from a cough.
“In response to the pandemic, there was an urgent need to assess the effectiveness of different sized breath shields,” said lead researcher Mong-Loon Kuet, MBBChir, FRCOphth. “We hope that the findings will further encourage the universal use of larger breath shields as an important part of a health care provider’s infection control measures.”
The team of researchers conducted a related study in May 2020 using a particle counter, which detects aerosols that are not visible to the naked eye. Both studies suggest larger breath shields are most effective at reducing infectious particle spread.
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