Humidity

Humidity quantifies the amount of water vapor present in air and is a critical parameter in HVAC design, thermal comfort, and industrial processes. Common measures include absolute humidity (mass of water vapor per unit volume of air), specific humidity (mass of water vapor per unit mass of moist air), and humidity ratio (mass of water vapor per unit mass of dry air). Relative humidity (RH) is the ratio of the actual partial pressure of water vapor to the saturation pressure at a given temperature, expressed as a percentage. Psychrometric charts are used to analyze humidity effects on cooling, heating, and dehumidification loads. High humidity can cause discomfort, condensation, and mold growth, while low humidity can lead to dryness and static electricity. Engineers use humidity control to maintain indoor air quality, protect equipment, and optimize energy efficiency.