When trying to destroy the slime on its biome, and therefore making a space with clorine to desinfect the slime, with a sink for the dups on their atmo suits as the clorine is unbreathable and it stings them in the eyes, they directly don´t wash their hands even if covered in slimelung. I have also tried with the washing basin or the hand sanitizer and the outcome is the same: dups with germs leave the atmo suit on its dock and remains with germs both duplicant and suit causing to spread through the base.
I´ve been reading through the last bug fixes and updates and I have not seen any feature saying that now the dups in atmo suits cannot use washing basin, sink... I´m really sure the feature was working on older uptates as I´ve been playing "ONI" for a long time. The same happens with some other people as i have read it on someones bug issue.
Just try to make a duplicant wash its hands when inside an atmo suit or other type of suit covered with germs.