1902: Electrically-powered air conditioning system
A printing works in New York installed an electrically-powered air conditioning plant designed by an American, Willis Carrier. The equipment could cool, heat and moisturize the supply air, which was a prerequisite for four-colour printing. Initially, the supply air was cooled using groundwater flowing through coils. However, in the following year, a special refrigerator was installed to manage this task. The equipment at the printing works was regarded as the first system that could be controlled in a reliable way.
1920s: Air conditioning units become common in the USA
After the tremendous breakthrough for electricity at the beginning of the 1900s, electrically-powered equipment began to be installed on a grand scale, especially in the USA where it became commonplace in industrial plants, hotels, theatres and cinemas. It is said that a contributing factor to the rise of the American film industry was the fact that cinemas could offer a few hours of relaxation in a pleasantly cool venue.