According to this study by the University of Cambridge, FFP3 masks provided "31-100% protection (and most likely 100%)": https://www.authorea.com/users/421653/a

According to this study by the University of Cambridge, FFP3 masks provided "31-100% protection (and most likely 100%)": https://www.authorea.com/users/421653/articles/527590-ffp3-respirators-protect-healthcare-workers-against-infection-with-sars-cov-2?commit=e567e67501cd6ee0dd1a6e8e4acdf2c4fd70e0ec https://www.authorea.com/users/421653/articles/527590-ffp3-r... (preprint).