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• Normal atmospheric air carries about 21% oxygen when inhaled. After gaseous alternate has taken vicinity within the lungs, with waste products (notably carbon dioxide) moved from the bloodstream to the lungs, the air being exhaled via human beings normally carries around 17% oxygen. This way that the human frame utilizes handiest around 19% of the oxygen inhaled, leaving over 80% of the oxygen available inside the exhalatory breath.

• This approach that there is extra than sufficient residual oxygen for use inside the lungs of the affected person, which then enters the blood.