Allegemine
Condensing water vapor as indirect evidence for air humidity]] An air mixture free of water vapor is called dry air. Tables on the composition of air usually refer to dry air, since the water vapor content of humid air varies comparatively greatly from 0 to 4 percent by volume. Air humidity is influenced primarily by the availability of [[water]], the temperature, and the degree of mixing in the atmosphere. Higher air temperatures allow for a higher water vapor concentration in the air. At very low concentrations of water vapor in the air, air humidity is also referred to as trace humidity or '''trace moisture'''. Rainer Müller: "Thermodynamics. From the Dewdrop to the Solar Power Plant." Walter de Gruyter, Berlin 2014, ISBN 978-3-11-030198-4.