Think about it. You have been transported back to the stone ages. How do you propose to live? Well to begin with, you might take up a club, go out and find yourself some wild animals and plants for your dinner. And you are bound to find plenty of unpolluted water down at the riverside. But hold your thought for a second and focus on how you are actually going to live. Food and water might not prove to be much of a problem, but the one thing you might not be able to face is the issue of shelter and comfort. Sure, you can find a nice little cave that suits you. But what are you going to do for comfort? There is an evil side to nature that many of us have not witnessed. At the maximum, most of us have faced torrential rains that lashed your place endlessly for days together. But what about river floods, hurricanes and worst of the lot, heat waves? The comforts of the modern day society have shielded people from most of these dreaded forces. The key to modern day comfort is the invention of air conditioning units. It allows humans to live completely in the safe, chilled, cool atmosphere of the air conditioned room, where the temperature and the humidity levels can be modified by the press of a button on the remote control. The history of air conditioning dates back to the Romans. There were many attempts at this kind of device right from mid-18th century. The first notable moment came when Dr. John Gorrie, an American physician, made a machine that blew air, using many wall fans, over a bucket containing crushed ice.

Perhaps the first break-through was achieved by Willis Carrier. Widely acknowledged to be the Father of Air Conditioning, his machine was called Air Treatment Machine, and used chilled coils to cool the air. This apparatus was able to lower the humidity to almost 50%. The major drawback of this apparatus was its huge and bulky size, and the use of poisonous ammonia as a coolant. This problem was overcome eventually in 1922, when Carrier replaced the ammonia with benign coolant dielene, and a compressor was added to the system. But the apparatus still remained very bulky and noisy for use in home. By 1928, air conditioners were installed in the offices of all the representatives in the White House, and soon the Supreme Court and the Senate followed suit. After the second World War, the sale of air conditioners increased by almost ten times in less than 8 years.