Wonder if this is still happening today?
H2O2 is technically "a bleach," and there are some alt health people who drink small amounts of it (cf. "The One Minute Cure"), gargle it, or nebulize it (cf. https://earthclinic.com/remedies/hydrogen-peroxide-inhalation-method/ ) and anecdotally helps them breathe.
I've seen experimental evidence that nebulized H2O2 can kill viruses in test tubes (PubMed) but no idea when it comes to humans.