What is optimal indoor air quality?
Humidity Heat Index
Not only temperature control, but humidity control also affects comfort.

Comfort zone defined by ASHRAE Standard*.
*ANSI/ASHRAE Standard 55-2010
Optimal humidity range for minimising adverse health effects

Source: Sterling, E.M., et al. ‘‘Criteria for human exposure to humidity in occupied buildings.’’
ASHRAE Transactions, 1985, vol. 91, Part 1.