There's the hamster test https://www.straitstimes.com/asia/east-asia/hamster-tests-show-masks-reduce-coronavirus-spread-scientists https://www.straitstimes.com

There's the hamster test https://www.straitstimes.com/asia/east-asia/hamster-tests-show-masks-reduce-coronavirus-spread-scientists https://www.straitstimes.com/asia/east-asia/hamster-tests-sh... Implies 60% protection of others when wearing a mask, and 30% protection of yourself.