What is psychrometrics? One Web site calls it the dreaded “Pword!”Psychrometrics is a subscience of physics dealing withthe properties and processes of moist air. Moist air is defined as amixture of two gases: dry air and water vapor (the gas phase of H2O). Some broaden the definition of psychrometrics to cover mixtures ofthe gas of one substance (any dry gas component) and the condensablevapor of a second substance. Psychrometrics is not confined tothe world of air conditioning. It is used in the fields of agricultural andaeronautical engineering, food engineering, drying of crops, grains,and pharmaceuticals, dehydration, dehumidification, humidification,moisture control, meteorology, and weather reporting.