<P> Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large - scale electrical air conditioning was invented and used in 1902 by American inventor Willis Carrier . The introduction of residential air conditioning in the 1920s helped enable the great migration to the Sun Belt in the United States . </P> <P> In 1758, Benjamin Franklin and John Hadley, a chemistry professor at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object . Franklin and Hadley confirmed that evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water . They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to speed up the evaporation . They lowered the temperature of the thermometer bulb down to − 14 ° C (7 ° F) while the ambient temperature was 18 ° C (64 ° F). Franklin noted that, soon after they passed the freezing point of water 0 ° C (32 ° F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 6 mm (⁄ in) thick when they stopped the experiment upon reaching − 14 ° C (7 ° F). Franklin concluded: "From this experiment one may see the possibility of freezing a man to death on a warm summer's day" </P> <P> In 1820, English scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate . In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida . He hoped to eventually use his ice - making machine to regulate the temperature of buildings . He even envisioned centralized air conditioning that could cool entire cities . Though his prototype leaked and performed irregularly, Gorrie was granted a patent in 1851 for his ice - making machine . Though his process improved the artificial production of ice, his hopes for its success vanished soon afterwards when his chief financial backer died and Gorrie did not get the money he needed to develop the machine . According to his biographer, Vivian M. Sherlock, he blamed the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor had launched a smear campaign against his invention . Dr. Gorrie died impoverished in 1855, and the dream of commonplace air conditioning went away for 50 years . </P> <P> James Harrison's first mechanical ice - making machine began operation in 1851 on the banks of the Barwon River at Rocky Point in Geelong (Australia). His first commercial ice - making machine followed in 1853, and his patent for an ether vapor compression refrigeration system was granted in 1855 . This novel system used a compressor to force the refrigeration gas to pass through a condenser, where it cooled down and liquefied . The liquefied gas then circulated through the refrigeration coils and vaporized again, cooling down the surrounding system . The machine produced 3,000 kilograms of ice per day . </P>

What type of gas is used in ac