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We inhale 420 litres of oxygen and exhale 350 litres of carbon dioxide per day. This gas exchange happens in the air sacs called alveoli which are over 600 millions and lined by thin membrane of 0.3 micron. These alveoli are connected by over 100–200 million patient branching bronchial to accommodate 10,000 litres of air and 10,000 litres of blood should circulate per day to carry oxygen to all the cells in our body. We need to breathe clean air to maintain our health.
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