 Oxygen is probably one of the commonest non-prescription drug used in the hospital and its advantage in several situations including carbon monoxide poisoning, central hypoxia and prior to planned intubation in an acute situation are today well-established and commonly used. Oxygen has been frowned upon in the resuscitation of newborn babies because of the risk of retrolental hypoplasia, now well accepted and adopted in clinical practice. Oxygen has also been traditionally used to increase oxygen carrying capacity in patients presenting with an acute coronary syndrome ACS, to reduce surgical site infections SSI, to ensure adequate oxygen delivery to tissues in unconscious patients, during cardiac surgery and for postoperative management, specifically after major surgery. Thus, deliberate use of high inspiratory oxygen concentrations e.g., 80 or above is recommended in the treatment of specific intoxications, such as with carbon monoxide or cyanide, wherein hyperbaric oxygen should also be considered. In addition, a high oxygen fraction has been suggested to prevent adverse outcomes after surgery and anesthesia, including a reduction in wound infections and postoperative nausea and vomiting PONV. In critically ill patients, oxygen delivery to the tissues is often compromised, and supplemental oxygen e.g., face mask with 10 L oxygen per min is commonly administered to patients with pneumonia, sepsis, acute coronary syndrome, or stroke - in fact, it is estimated that oxygen is given during transport in approximately one-third of all ambulance journeys. 