Humidity control in Museums, Archives and Libraries

The air-conditioning systems in old buildings are not always able to maintain the air conditions required for the conservation of certain materials.

What sort?

  • Old books, dried animals and animal parts, dried plants, textile materials, paper, paint on canvas and parchments, photographs, films, wooden objects.
  • Valuable materials susceptible to corrosion: Historical tools and machinery.

Dehumidifiers must be installed to dry the exterior air currents from the mechanical ventilation systems and from infiltration as well.

This is turn provides the following advantages :

  • It enables the control of Relative Humidity regardless of the exterior climatic conditions.
  • The improvement can be made without having to detain the current installation.
  • The treated air flow is not equivalent to the total for the Air Handling UnitA.
  • It is only necessary to treat the exterior air supply (between 5% and 10% of the total volume). The dehumidification unit will therefore be smaller and cheaper.
  • A basic humidistat turns the dehumidifier on and off. Energy is saved because it is not consumed when the exterior air conditions do not require drying.


  • Elimination of mould, which can appear and cause damage to certain organic materials such as books, and dried fauna and flora.
  • Prevention of the reappearance of salts on the surface of dried animals (reducing the effects of their disinfection), as well as on the surface of old pieces of metal, to stop bronze disease for example.
  • If the visitor area is treated, controlling humidity adds to the comfort levels of visits. Low humidity in winter can cause excessive cold.
  • Prevention of unpleasant odours from mould.
  • Low Relative Humidity reduces the presence of insects and avoids damage caused by condensation in buildings.

Storage conditions:

One of the world's finest pieces of architecture is the La Alhambra Palace in Granada, Spain. Its construction is a magnificent example of Andalusian Moorish art perfectly adapted to its natural setting. FISAIR's DFRB series desiccant rotor air dehumidifiers have been installed in the palace in order to reap the benefits described aboves.