Science and technology of the Tang dynasty
The inventor Ding Huan (fl. 180 AD) of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered. In 747, Emperor Xuanzong had a "Cool Hall" built in the imperial palace, which the "Tang Yulin" (唐語林) describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty, written sources mentioned the air conditioning rotary fan as even more widely used.
Weather Eye
In 1939, Nash added a thermostat to its system, making it the first thermostatic automobile climate control system. The Weather Eye "was the first truly good heating and ventilating system." Additionally, defoggers (defrosters) were incorporated with the introduction of the 3900 series cars that year. The Nash HVAC system was designed by Nils Eric Wahlberg and it continues to be the basis for use in modern automobiles. Nash included the first automatic temperature control for the airside of the heating system with the thermostat sensing the temperatures of the incoming outside air, the heater's discharge, and interior of the car; so that a change in any of these three air temperatures resulted an automatic adjustment to maintain passenger comfort. Nash's Conditioned Air System heater was now marketed as the "Weather Eye" and consumer sales literature explained that the thermostat's "mechanical eye" watched the weather, hence the name.