Humidity affects many properties of air, and of materials in contact with air. Water vapor is the key agent
in both weather and climate, and it is an important atmospheric greenhouse gas. Humidity measurements
are used wherever there is a need to prevent condensation, corrosion, mold, warping or other spoilage of
products. This is highly relevant for foods, pharmaceuticals, chemicals, fuels, wood, paper, and many
other products. Air-conditioning systems in buildings often control humidity, and significant energy may go
into cooling the air to remove water vapour. Humidity measurements contribute both to achieving correct
environmental conditions and to minimising the energy cost of this.