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Relative humidity from dry and wet bulb temperatures- degrees Celsius (pdf)Īltitude and Correction Factors Moist Air - Barometric Altitude and Correction Factor Barometric Altitude.Relative Humidity Chart - degrees Celsius Relative humidity from dry and wet bulb temperatures- degrees Fahrenheit (pdf).Relative Humidity Chart - degrees Fahrenheit M ws = mass of water vapor required to saturate at this volume M w = mass of water vapor in the given air volume Relative humidity can also be expressed as the ratio at actual mass of water vapor in a given air volume - to the mass of water vapor required to saturate at this volume. If the actual vapor density at 20 oC (68 oF) is 10 g/m 3 and the saturation vapor density at this temperature is 17.3 g/m 3, the relative humidity can be calculated as Ρ ws = vapor density at saturation at actual dry bulb temperature Ī common unit for vapor density is g/m 3.Įxample: Relative humidity at a given temperature and known vapor density and saturation density Relative humidity can also be expressed as the ratio of the vapor density of the air - to the saturation vapor density at the the actual dry bulb temperature. If the vapor pressure in the actual air is 10.3 mbar the relative humidity can be calculated as: As we can see the maximum water vapor pressure - the saturation pressure - is relatively small.Įxample: Relative Humidity and Vapor Pressureįrom the table above the saturation pressure at 70 oF (21 oC) is 25.0 mbar. Note! The atmospheric pressure of air is 1013 mbar (101.325 kPa, 760 mmHg). If the water vapor pressure in the air is 10.3 mbar, the vapor saturates on a surface with 45 oF (7 oC). Air - Saturation Vapor Pressure - (Celcius and milibar) (pdf).Moist Air - Saturation Vapor Pressure Temperature