|Measures and Instruments|
Psychrometrics, psychrometry, and hygrometry are names for the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures. The term comes from the Greek psuchron (ψυχρόν) meaning "cold"  and metron (μέτρον) meaning "means of measurement". 
Although the principles of psychrometry apply to any physical system consisting of gas-vapor mixtures, the most common system of interest is the mixture of water vapor and air, because of its application in
Many substances are
In industrial drying applications, such as drying paper, manufacturers usually try to achieve an optimum between low relative humidity, which increases the drying rate, and energy usage, which decreases as exhaust relative humidity increases. In many industrial applications it is important to avoid
Molds and fungi can be controlled by keeping relative humidity low. Wood destroying fungi generally do not grow at relative humidities below 75%.