Air conditioning has been around since Roman times, when the wealthy piped aqueduct water through pipes in their walls.
In 1902, a Cornell-trained mechanical engineer named Willis Carrier (1876-1950,) building on Michael Faraday’s discovery in 1820 that compressing and liquefying ammonia would chill air when the liquefied ammonia was allowed to evaporate, developed the first practical air conditioner.
Carrier’s invention controlled both air temperature and humidity, and was first installed at the Sackett-Wilhelms Lithographing and Publishing Co. in Brooklyn, New York, where it made possible aligned four-color printing and stable paper dimensions
Over the next several years, air conditioning made slow and steady gains in printing plants, textile mills, pharmaceutical plants, and a few hospitals, but the technology was very expensive, and the coolants used, ammonia, methyl chloride, and propane, and could result in fatal accidents if they leaked into the environment.
By 1923, Carrier, now using the relatively-safe dielene (dichlorethylene) as a coolant, had invented a new type of system he thought would be perfect for movie houses. In the heat of the summer, many theaters were forced to close because of the stifling heat inside. Even on cool days, the houses were uncomfortably warm, and ventilation systems were of limited use. Against this backdrop, Carrier argued that a theater with air conditioning could run any kind of movie and the public would buy a ticket just to keep cool.
Carrier installed air conditioning systems in three small theaters in Texas, and in 1924 landed a contract to replace the aging ventilation system in New York’s Rivoli Theater with air conditioning. The installation was completed in May of 1925. No less a personage than movie mogul Adolph Zukor pronounced it a success, and by the mid ‘30s, almost all theaters were “cooled by refrigeration.”
In the late 1920s, a research team was formed at General Motors by Charles Franklin Kettering (inventor of the electric starter and about 180 other things) to find a replacement for the dangerous refrigerants then in use. In 1928, they synthesized Freon (dichlorodifluoromethane) a safe, non-toxic coolant which Carrier immediately adapted for use in smaller and less expensive home units. In 1945, Robert Sherman of Lynn, MA invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air, eventually leading to the central heating and air we have today.
Air conditioning literally tamed the Southern and Southwest United States, and led to the emergence of huge cities such as Miami, Phoenix and Las Vegas.