Oxygen

"So Harry, thinking that he would soon have had enough of the library to last him a lifetime, buried himself once more among the dusty volumes, looking for any spell that might enable a human to survive without oxygen. However, though he, Ron, and Hermione searched through their lunchtimes, evenings, and whole weekends — though Harry asked Professor McGonagall for a note of permission to use the Restricted Section, and even asked the irritable, vulture-like librarian Madam Pince, for help — they found nothing whatsoever that would enable Harry to spend an hour underwater and live to tell the tale."

- Description.

Oxygen is a chemical element. In nature, at standard temperature and pressure, oxygen molecules bind to form dioxygen, a very pale blue gas with no smell or taste. Oxygen supports life, as it is a majority part of the Earth's atmosphere and comprises most of the mass in water.

Humans do not survive without oxygen, and it seems there are no spells capable of enabling humans to live without inhaling oxygen. The Bubble-Head Charm, however, might turn one's exhaled air (which is rich in carbon dioxide) back into oxygen-rich fresh air, otherwise users would suffocate in due course while using the spell.

Appearances

 * Harry Potter and the Goblet of Fire