"William Noble" wrote:

You MAY be right, but I don't think so - the things fit nicely over one's
mouth, but not over one's nose or certainly not nose and mouth, so that
would suggest it's not for anesthesia - but it might be part of a pilot's
breathing aparatus where one could reasonably breathe through the mouth, or
it might go with a separate rubber seal and cover more volume - all in all,
quite a mystery. -

Mouth or venting the pecker. Wash before experimenting