In my days as a first aid person, I would change the mask on the doll we used for our resuscitation exercises based on hygiene. We had a collection of masks in the group and would sterilise them after use.
We are no longer unmasked so much. We do not use them on dummies anymore. We wear them ourself to keep us and the others protected. I left my first aid group a few years ago. I wonder if they still practice with these masks. Now they have the real thing.