Answer: Willis Carrier

Over the centuries, humans have come up with ingenious ways to stay cool. Ancient Egyptians used dampened reeds hung in windows to create primitive evaporative coolers. In Ancient Rome, water from aqueducts was circulated through the walls of certain homes to cool them. Persians made use of cisterns and wind towers to cool their buildings during hot weather. Massive rotary fans powered by prisoners, and later by water, were popular in ancient China.

Anything closely resembling modern air conditioning didn’t appear until advances in chemistry occurred in the 19th century, however. Experiments throughout the 19th century, like those conducted by Michael Faraday with compressed and liquefied ammonia, paved the way for the invention of the first electromechanical air conditioner in 1902. It was then that Willis Carrier, while experimenting at the Buffalo Forge Company, created a mechanism for controlling not only temperature, but humidity as well in his quest to solve process control issues in a printing plant (consistent temperature and humidity were important to keeping the paper and ink within specifications).

It wasn’t long before Carrier and others realized the utility of his invention beyond controlling the conditions for printing presses and, over the ensuing decades, electromechanical air conditioning went from a massive and expensive affair reserved for industrial processes to a compact and inexpensive addition to office buildings, homes, and automobiles.