Indices of Water Content in Gaseous Systems, Their Measurement, and Relationship to Each Other

The quantity of water available to microorganisms influences both their growth and death kinetics. The water in microbial cells cannot be measured directly. The equilibrium atmospheric water conditions are usually measured and reported. The attributes of the several measuring units that can be used to indicate the water content in a gaseous atmosphere are described. Equations for their calculation and for converting from the several measurement units described to relative humidity at test temperature are presented.