The Importance of Humidity Control in Museums and Archives

It is commonly acknowledged by preservation experts, that inappropriate water vapour in the air are a real threat to the preservation of documents, artifacts and relics. 

Humidity can lead to moisture damage, bacterial growth and corrosion of the object to be preserved. Once, this has occurred the object will probably never return to its former condition.

NEWS: World's Oldest Mummies damaged by humidity

In an recent article posted in the Guardian, the world's oldest mummies are degrading at a rapid rate due to higher than normal humidity levels in the atmosphere. 

Ralph Mitchell, a Harvard microbiologist and a team of Chilean researchers found that bacterial “opportunists” were taking advantage of a more humid environment, which has enabled the bacteria to start to consume the ancient relics. These were common skin bacteria, among others, that had been enabled by a particular set of environmental conditions (higher humidity).

Chinchorro mummy of a child on display during an exhibition at La Moneda presidential palace, Santiago. Photograph: Claudio Santana/Getty

Chinchorro mummy of a child on display during an exhibition at La Moneda presidential palace, Santiago. Photograph: Claudio Santana/Getty


Control Humidity with Air Solutions

The key in this saga is that humidity, temperature and pollutants are important factors in preserving documents. And, in general the humidity and temperature have to be as stable as possible and pollutants should be kept to a minimum in order to keep artifacts in the best condition possible.

Air Solutions provides the solutions to this problem using desiccant dehumidifiers. Desiccant dehumidifiers are used world wide protect film, tapes, documents, books, and artifacts in archives, museums, and libraries. With dehumidification we physically remove the moisture from the air, meaning that corrosion and mould growth are unable to occur.

If you would like to find out how we can help with your application, please contact us or call 0800 433 486


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Whether you have a natural history specimen, textile, paper, book, manuscript, print or any other ethnographic (made from wood, leather or ivory) material, all such materials are subject to a natural process of decay. As they are all organically based they are susceptible to mould growth and rapid deterioration, particularly in a warm, moist environment. By removing the moisture from the environment the damaging effects can be eliminated when relative humidity is kept under control.



The long term storage of paper and film records needs very special conditions. For example old flammable nitrate film shrinks and decomposes with age and needs to be carefully copied onto modern safety film if it is to be preserved. Humidity is a key factor affecting acetate film degeneration. The optimum conditions required are 30% Relative Humidity at 20°C if the safety of the stored film is to be guaranteed. Extensive research work has shown that, without doubt, humidity is the most significant factor affecting acetate film degradation.



Ferrous and non-ferrous metals and alloys corrode rapidly in the presence of water vapour. Moreover, the rate of corrosion is further accelerated by natural or industrial pollutants in the air. Bronze, for example can develop the phenomenon known as ‘Bronze Disease’ breaking into active corrosion if relative humidity is too high. Metal which is already severely corroded may require the maintenance of a relative humidity below 40% but usually corrosive activity is significantly reduced below 60% RH.



The maintenance of precise relative humidity levels is, of course essential if 16th and 17th Venetian glass (circa 1676 to 1680) is to be displayed and stored safely. When the relative humidity is inappropriate, ‘weeping or crizzling’ occurs due to the reaction of unstable constituents of the glass with the water vapour in the air. Extensive research has ascertained that glass and ceramic objects are best protected in an environment where relative humidity is between 40% and 60%.