Why can a person who needs extra oxygen just breathe the air?
as others have said the air is not made of pure oxygen, in fact oxygen comprises around 21%. air can include other chemicals such as pollutants. if a person is being put on oxygen then usually it means their respiratory tract is compromised ie the person is unable to extract sufficient ixygen formt eh air via the lungs that could be caused by numerous factors the airflow could be compromised by asthma, difficutly in breathing damage tot the liming of the lungs, this could be genetic, it could be due to smoking, smoke damage, or as a symptom of other illnesses leading to fluid in the lungs the cardio vascular system may not be pumping the blood around fast enough meaningthere is insufficient gas transfer in the lungs the red blood cells, which carry the oxygen, may be compromised, if for instance the person is a smoker or has been inhaling carbon monoxide which binds preferentially to the haemoglobin meaning there is less capacity to transfer oxygen.
