An effect of inhaled temperature on thermal comfort, perceived air quality, acute health symptoms and physiological responses

We explored the importance of inhaled air temperature on thermal comfort, perceived air quality, acute non-clinical health symptoms, and physiological responses. Sixteen subjects stayed in a stainless-steel chamber for 90 min. They experienced four conditions with two inhaled air temperatures of 22 ℃ and 30 ℃ and two ambient temperatures in the chamber of 22 ℃ and 30 ℃ in a 2x2 design. They wore breathing masks covering their mouth and nose to control the inhaled air temperature; the air was provided from an adjacent twin stainless-steel chamber. The subjects evaluated thermal conditions and health symptoms on visual-analogue scales. Skin temperature and electrocardiography were recorded. Perceived air quality was significantly improved when subjects sat in the chamber at 30 ℃ and inhaled air with a temperature of 22 ℃; under these conditions lip and throat dryness were significantly reduced. The lower inhaled air temperature increased time-domain heart rate variability indicators and decreased heart rate and the LF/HF ratio, suggesting that the parasympathetic nervous system was activated and the sympathetic nervous system was suppressed.