AND HEALTH

Human physiology is not adapted to the climatic conditions in temper-ate and polar latitudes, although parts of these regions have been popu-lated for several thousands of years. The ideal ambient temperature for a naked person at rest is about 29°C, a climatic condition found in the mountain and savannah landscapes of Africa, the probable origin of our ancient ancestors. Without clothing and shelter, man could be regarded as a tropical animal that can only survive in a narrow zone along the equator. When our forefathers migrated north not only was proper clothing needed but a protective climatic shield also had to be devel-oped: housing and building technology were adapted to very challeng-ing winter climates. Originally, we were also biologically adapted to con-tinuous supplies of fresh outdoor air for breathing and keeping our bod-ies cool. The term “indoor environment ” is a consequence of the need for shelter against wild animals and – as Mankind moved to more weath-er-beaten areas – against unfavourable outdoor climates. Indoor air qual-ity, however, depends on a number of factors, including the outdoor air quality, the amount of fresh air provided indoors and the amount of air pollution derived from numerous indoor sources. On average, an adult male with a sedentary occupation will breathe about 15 m3, or roughly 15 kg of air, drink 1.5 litres, or 1.5 kg, of water and eat about 0.75 kg of solid food per day. Hence, the weight of breathed air constitutes about 87 % of the total biological mass turnover every 24 hours. Clothing and a building envelope provide two vital levels of shelter between the human organism and its surroundings. Indoor environ-ments are not only vital for our survival, health and well-being but also constitute the greater part of human environmental exposure