The common Chemical Reaction in which Oxygen unites with another substance is called Oxidation.Combustion or rapid oxidation, the burning of s substance may generate light and heat. The process called Oxidation need not involve generation of light and heat. Oxygen itself does not burn. The Respiration of plants and animals is a form of Oxidation that is essential to the liberation of the energy stored in such food materials as Carbohydrates, Fats, and Proteins. Oxygen is necessary to sustain Metabolism which primarily involves the Oxidation-Reduction Chemical Reactions. If the Oxygen concentration were to drop to about half its value in the atmosphere, humans could no longer survive. The loss of Oxygen is critical as the human body has no means of storing Oxygen. Because the human body stores no Oxygen, any interference with breathing and ventilation that lasts more than a few minutes can cause Death.
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