Psychrometry is the study of the air and its properties. The properties of temperature, humidity, vapor pressure and dew point are measured to evaluate air conditions and determine whether intervention is needed to prevent damage to materials. Psychrometrics (another name for "psychrometry") evaluates how these properties of air relate to the effects that moisture has on various structural materials and contents.
Water damage restoration professionals need a thorough understanding of psychrometrics to dry a structure and its contents effectively. Water damages materials in two ways: (1) from absorption of water in direct contact with materials and (2) from absorption of excessive moisture in the air. Measuring the moisture content of the air is critical to the drying process. High humidity conditions result in slow drying, while low humidity enhances drying. Changes in air temperature effect the capacity of air to hold moisture and thus increase or decrease the rate at which water evaporates into air.
Restoration professionals must establish an environment favorable for drying. They must understand how to manipulate temperature and humidity levels to produce optimum drying conditions, without causing secondary damages through excessive humidity. Temperature is controlled through the structure's air conditions and heating systems or through portable heating systems. Low humidity is achieved through air movement and dehumidification. Air movers evaporate moisture from structure and contents into the air, while various sizes and types of dehumidifiers remove moisture from the air.