Building and maintaining a repository with appropriate environmental conditions for the long-term preservation of archives can be an expensive process, especially in countries with tropical climates. Indeed, it can be a process that is beyond the financial means of some countries. This article describes the process of using storage containers as low-cost alternatives to more expensive permanent buildings. Storage containers are readily available in most countries and can be acquired, installed and maintained at a relatively low cost.
Regardless of the type of facility used, it must protect the records stored there from dust and other contaminants. In addition, tropical repositories must also protect records from the effects of:
- high levels of temperature and relative humidity;
- salty sea air;
- high levels of precipitation;
- cyclones (hurricanes or typhoons), storms and lightning strikes; and
- pest infestations.
Choosing and purchasing the archive storage container
When a storage container is evaluated for purchase, it must be thoroughly inspected to ensure that it is in good condition. There should be no rust, gaps or leaks. Doors should be checked to ensure that they move freely and form a reasonably tight seal when closed. The marine storage container should maintain a sealed internal environment to ensure stable conditions and to protect against the intrusion of rain, dirt and dust, insects and other pests.
It is easy to tell if the container is leaking by the amount of daylight entering the container when its doors are closed. Of course, it is preferable that the inspection be carried out on a sunny day.
In addition to the purchase cost, there will also be expenses associated with moving the container to its new location and setting it up.
How much storage capacity for the archives?
The standard 20-foot container has an internal storage capacity of 29.50 cubic metres. What will be achieved in terms of linear storage depends on how efficiently the boxes are arranged. A balance will have to be found between maximum storage capacity, ease of access and retrieval and good ventilation.
It is assumed that the boxes used will conform to the dimensions of a standard National Archives Type 1 box (i.e. 390 mm x 260 mm x 180 mm).
The boxes should ideally be placed on shelves or racks and not simply stacked on top of each other. If it is possible to stack them seven or eight high, there is always the risk that the lower layers will be crushed under the weight. If this method is to be adopted, thick layers of cardboard on each level should be used to distribute the weight.
The advantage of not using shelving means that more boxes can be stored at a lower cost. The disadvantage is that if access is required to a particular box (for example, the box on the lower level) the installation will have to be dismantled to access that box.
Controlling Pest Infestations to Protect Archives
As the boxes are inserted into the container, they should be inspected for signs of moisture, mould or pest infestation. Otherwise, a problem could easily be imported.
Once established, boxes of moisture absorbing crystals such as Damp Rid or Closet Camel should be placed inside the container to help control excess moisture. Bait and gaff traps should also be included for insects and other pests. These items should be checked regularly and replaced if necessary.
Controlling environmental conditions to maintain the archives at the right temperature
The biggest environmental problem for archive storage in the tropics is mould, whose growth is promoted by high humidity levels. Reasonable temperatures can be maintained in a container if it is protected from direct sunlight and if there is good air circulation around and through it using fans.
A mechanically refrigerated (air-conditioned) container will keep the temperature lower and reduce humidity levels. However, such a unit is more expensive to purchase and operate than non-air-conditioned units. Another negative side effect is that condensation can occur when warm, moist air from outside the container comes into contact with the cooled internal metal surfaces.
Mechanical refrigeration consumes significant levels of electricity. This can lead to unacceptable voltage drops on power supply lines that are not sufficiently dimensioned for this purpose.
Portable dehumidifiers can help control humidity levels. They require less energy to operate than mechanically refrigerated units, but it is necessary to empty their condensate tanks at regular intervals.
Monitor environmental conditions
The environmental conditions inside the container should be monitored regularly. This can be done in several ways.
Portable electronic data loggers can be used. Only one or two would be required. They are powered by a lithium battery and can monitor conditions continuously for more than a year. The results can then be downloaded to a computer system.
Older-style thermo-hygrographs can also be used, but they should be monitored more closely, with readings noted and graph paper replaced.
The site must be kept clear of vegetation and leaves (as previously stated), as must the roof structure.
If the mains water supply is available, a hose point and hose can be provided. Hand-held pressurized water extinguishers should also be provided.
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