Humidity is the amount of water vapour (moisture) in the air at a given temperature. Water vapour is the most important gas as far as weather is concerned. High humidity means there is a great deal of water vapour in the air; low humidity means there is very little water vapour in the air.

Humidity is measured as a percentage called relative humidity (RH). At RH of 100% the air is to be said saturated.

The amount of water vapour that air can hold is dependent on the temperature of the air. The hotter the air, the more moisture it can hold, so that when the air is warm the air can hold more water vapour. Cold air is more dense than warm air and cannot hold as much water vapour.

Air contains ≈20% Oxygen and ≈80% Nitrogen concentration by volume. Water evaporation rate is inversely proportional to vapor temperature, pressure and air density.

At sea level: Air at 30°C can hold 28 grams of water vapour per cubic metre of air. Air at 10°C can hold 8 grams of water vapour per cubic metre of air.


Moisture presents a serious threat to product integrity in a variety of industries. Fungus, mildew, odors, discoloration, oxidation (rust) and product deterioration are the damaging consequences of moisture contamination.

Controlling humidity in an enclosed space can be important for a wide variety of reasons. Most common applications include, process improvement for manufacturing sectors (such as confectioneries, electronics, and pharmaceuticals), product protection from degradation (some foods, grains and seeds), protection from corrosion, and limiting moisture damage during marine transport.

The need of humidity control is essential for minimizing spoilage losses.

A desiccant is used to adsorb moisture in preventing products from moisture-induced damage, despite, maintain product stability and extended shelf life.