Humidity is water vapour present in an air mass. There are four generally accepted expressions of humidity used in the water damage restoration industry;
- Humidity Ratio (HR)
- Relative Humidity (RH)
- Water Vapour Pressure (WVP)
- Specific Humidity (SH)
The most common expression is ‘relative humidity’; relative humidity is the amount of moisture contained in a sample of air as compared tp the maximum amount the sample of contain at that temperature. This definition is accurate in concept; but strictly speaking, relative humidity is the ratio of the partial pressure of water in a sample of air to the water vapour pressure at saturation of that air at a given temperature and atmospheric pressure.
Please see below, Pressure vs Temperature Diagram;