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" () 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.
Povl Ole Fanger
Povl Ole Fanger (July 16, 1934 – September 20, 2006) was an expert in the field of thermal comfort and perception of indoor environments. He was a senior professor at the International Centre for Indoor Environment and Energy at the Technical University of Denmark. He was a visiting University Professor at Syracuse University when he died at the age of 72 from an abdominal aortic aneurysm. His work is credited with demonstrating that poor air quality in homes can cause asthma in children, and that poor air quality in workplaces decreases productivity. His contribution to the research on thermal comfort still defines the state of the art in HVAC technology and the basis for international standardisation. He is also known for creating indoor air quality (IAQ) units of measurement known as the olf and decipol.