The process of breathing involves taking in oxygen rich air and giving out carbon dioxide rich air.the entire process occurs through the action of the various organs of the respiratory system.the respiratory rate or speed of respiration varies with age.a normal pre-school child has a respiratory rate of 20-30 breaths per minute whereas a normal adult has a respiratory rate of 12-20 breaths per minute.the fuel used for respiration is glucose because glucose synthesized during the process of respiration is used for utilization and production of energy. so, respiration is a continuous process which makes us able to meet energy demand of our body. if it comes to halt , the person will die.