What People Are Asking: What is the history of air conditioning?

Dear Librarian: Air conditioning has got to be one of the best inventions ever. What can you tell me about its history?
Dear Reader: Especially during the hot, humid months of summer, there are few inventions I am more thankful for than air conditioning. Many of us take it for granted, but there is a lot more to it than just flipping a switch. It is really a complex electromechanical system which took nearly a century of engineering development in cooling, thermodynamics, controls and energy efficiency to create.
Early on, man tried to keep cool by building architecture designed to take advantage of natural ventilation like building in the shade, or including many windows and doors in a structure. However, in warmer climates or seasons, this was little help so other ideas were needed.
An inventor in second century China, named Ding Huane, crafted a manually powered rotary fan. Leonardo da Vinci made the first mechanical ventilating fan around 1500. An American physician, Dr. John Gorrie, designed a machine to cool down hospital rooms for patients in the 1830s. Essentially, the machine fanned air across a container of ice. To help dying President James Garfield in 1881, naval engineers constructed a device that blew air through cloth soaked with melted ice water. Although the invention could lower the room temperature by 20 degrees, in two months it used a half million pounds of ice.
Then genius struck. In 1902 Willis Carrier solved one of mankind’s toughest challenges. Inspired, while waiting on a foggy train platform, he realized he could dry air by passing it through water to create fog. This would make it possible to produce air with specific amounts of moisture in it. Controlling humidity is the building block of modern air conditioning. Carrier’s invention sent air through coils filled with cold water. This cooled the air and removed moisture to control humidity.
The first air conditioners were very large, expensive and dangerous because ammonia was used as a coolant and was highly toxic. However, in 1922, Carrier made two important breakthroughs. One, he replaced ammonia with a much safer coolant. Two, he was able to reduce the size of the units, which led to them being installed in more places.
In 1933, Carrier’s company developed a model that used a belt-driven condensing unit and associated blower, mechanical controls and evaporator coil. Although today’s air conditioners have improvements, they still operate on the same fundamental science concepts as Carrier’s 1933 system.
The invention of air conditioning, and the ability to control the temperature and humidity levels indoors, has led to countless things. Many industries benefited from improved working conditions and productivity. The film industry boomed when theaters became a place people could go to escape the heat. In World War II, thousands of walk-in coolers kept food and perishables fresh. After the war, it allowed sky scrapers and other unconventional structures to be built and it transformed houses, especially in the South. Migration increased. Huge cities and suburbs cropped up where once there had only been small towns. Death rates have dropped, and economic activity in the summer months has soared.
Refrigeration technology has also allowed trips to the moon and other space exploration, shopping malls, transatlantic flight and the computers and servers that power the Internet. Air conditioning has become a necessity in nearly every human endeavor.