Here's the grand-daddy study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7680614/ It has been "retracted," but the statements about influenza were not, and it now states that "approved" masks work. Ask what "approved" masks are. Here's one that states that they help prevent spreading by an infected person, but they don't really talk about anything else. https://pubmed.ncbi.nlm.nih.gov/33087517/ The best one from SARS-CoV-1 in 2003: https://www.smh.com.au/national/farce-mask-its-safe-for-only-20-minutes-20030427-gdgnyo.html