\(\textit{Absolute Humidity}\) is an amount of water vapour, usually discussed per unit volume. Absolute
humidity in air ranges from zero to roughly 30 grams per cubic meter when the air is saturated at \(30 ^\circ C\). The absolute
humidity changes as air temperature or pressure changes. \[\] This is very inconvenient for chemical engineering calculations,
e.g. for clothes dryers, where temperature can vary considerably. As a result, absolute humidity is generally defined in
chemical engineering as mass of water vapour per unit mass of dry air, also known as the mass mixing ratio, which is much more
rigorous for heat and mass balance calculations. \[\] Mass of water per unit volume as in the equation above would then be
defined as volumetric humidity, because of the potential confusion.
\(AH = \frac{\mathcal{M}_\omega}{\vee_{net}}\), where \(\mathcal{M}_\omega\) is the mass of water vapour per unit volume of total air and \(\vee_{net}\) is water vapour mixture.