5 ways dehumidifiers are being used in storage preservation and archiving

From preserving archives hidden within a labyrinth of mines, to storing aerospace components before they take to the skies, here are just some of the environments where the right systems can prevent ongoing problems caused by excess moisture:

#1 Helping a decommissioned water station stay dry

Blagdon Water Station, near Bristol in the UK, welcomes over 25,000 guests to its visitor’s centre every summer. A former pumping station, the building features a set of beam engines that would have pumped water from the Yeo river during the early 20th century.

With a constant influx of people during peak season, temperatures rise and fall, and humidity levels fluctuate. When the centre was closed throughout the winter, the cold, poorly ventilated space meant that condensation, damp and rust began to cause issues. To protect this piece of industrial history, relative humidity needs to be regulated all year round.

Relative humidity (RH) tells us how much water vapour is in the air in relation to how much it could potentially hold at that temperature. Because warm air can hold more moisture than cold air, the percentage we see is not a direct measure of the amount of water vapour present. For example, there will be more moisture in the air at 50% RH when the temperature is 25°C than there would be at 10°C.

When air rapidly cools, RH levels are more likely to reach 100%, or ‘dew point’. This means that the air, at its current temperature, has reached its maximum water content and will release excess moisture in the form of condensation. Inside buildings, this often happens when saturated air comes into contact with cold surfaces like metal or single-glazed windows.

To maintain optimum RH levels, Bristol water installed a Calorex DH 150 dehumidifier. Self-contained with fully automated operation, the unit circulates humid air around the room and removes harmful moisture before condensation strikes.

#2 Protecting irreplaceable artworks

Dean Hill Bunkers, in the UK, started life as a naval armaments depot, but today the facility is used for high-security storage by a number of national arts organisations.

Hidden away in a network of tunnels, the bunkers have been converted into five storage vaults. The lack of sunlight, protection from the elements and accessibility via internal entrance tunnels make the facility an ideal space for protecting sensitive materials. However, if humidity is unregulated, moisture damage can become a danger.

While humidity may usually be associated with warm environments, cold unventilated spaces, such as underground tunnels, are extremely susceptible to damp and condensation caused by saturated air.

RH levels will affect different materials in different ways. For example, wood will expand or contract, metals will rust, and old nitrate film will deteriorate much quicker.

Humidity levels should be optimised for the specific items inside a space, but the examples below may serve as a useful guide in achieving the best conditions for materials commonly used to create works of art:

Material	RH%	T(°C)
Paper and paper-mache	50-60	19-24
Marble and stone	45-60	<30
Videotapes	30-50	-5 to 15
Photographs	20-30	2-20
Wood	40-65	19-24
Paint on canvas	45-60	19-24
Paint on wood	45-55	19-24

To ensure safe storage of the irreplaceable items in their care, each vault at Dean Hill Park is equipped with a Calorex DH 150AX dehumidifier with four-sided louvered grills.

#3 Preventing the corrosion of aerospace components

Preci-Spark delivers components, complex fabrications and assemblies for the latest commercial aircraft engines and semiconductor equipment.

During storage, moisture in the atmosphere makes rust a constant threat. While rust will gradually take its toll over long periods of time, the corrosion of steel will accelerate dramatically when relative humidity levels exceed 50%.

• At an RH of approximately 50% or below, virtually no corrosion occurs

• With an RH of 60% and over, the rate of corrosion on steel rises rapidly