March 2017
Intermediate to advanced
592 pages
17h 6m
English
Breathing is involuntary activity of human life. A healthy person never thinks about the breathing action although air is one of the most important five essentials (air, water, food, heat and light) for human survival. A healthy human being breaths nearly 22,000 times a day inhaling approximately 15 kg (12.4 m3—at 20°C, 1 atm) of air. One estimate says a healthy human being can survive 5 weeks without any food and 5 days without any water. Without an air, it is anyone’s guess. It may not be possible to survive even for 5 minutes without air. Air, a natural resource, is abundantly available over the surface of the Earth, free of cost. Although a must for human survival, it has long been an ...
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