When was the First Central Air Conditioning Heating Unit Made?
By the 1920s, smaller air conditioning units were appearing in private homes. Theatres, department stores, hospitals, banks, and offices were already using air conditioning-the bigger places used a central air conditioning system devised by the Carrier Corporation. When the Depression of the 1930s hit, not many air conditioning units were sold, but after the Second World War, things picked up. Nowadays if you live in a really hot place in North America, not having air conditioning is unusual.
