hours oxygen for benefit
If your lungs are healthy, and you have no breathing difficulties, your body has all the oxygen it needs, says Boyer. In hospital settings, 100% oxygen may be delivered -- but even then only on a short-term basis, says Boyer -- less than 24 hours and preferably less than 12 hours. To breathe pure oxygen at that level for any longer can have toxic results, including shock lung, or adult respiratory distress syndrome.