The practical application of scientific air conditioning to various industrial processes and manufacturing methods and equipment first became evident about 1905. Air conditioning for human comfort was provided originally about 1922 in motion picture theaters and during the last ten or fifteen years has been made available with gratifying results in restaurants, stores, hotels, private homes, office buildings and railroad cars. Air conditioning may be defined as the mechanical production of an artificial indoor atmosphere through the simultaneous and complete control of temperature, humidity, movement and purity during various seasons of the year. While proper ventilation in general is recognized as one of the essentials for the maintenance of indoor life and health, little scientific information or statistical data are available as to the influence of complete air conditioning on the health of industrial workers.
AIR CONDITIONING SYSTEMS
There are various types of so-called air conditioning systems now in vogue.