W.H. Demmons W.H.

Indoor air quality can preserve and protect.

Imperative to any good archival storage HVAC system is the control of air pollution, temperature, and relative humidity, which are all critical in the preservation of historical artifacts, as without these being properly controlled the breakdown of materials will happen at an accelerated pace.

Furthermore, heat accelerates deterioration, and high relative humidity in combination with high temperature encourages mold growth and insect activity.

A quality HVAC system can also be significantly enhanced by properly sealing the archive room, eliminating natural light, using approved lighting fixtures, and using proper moisture barriers and insulation.

Typically, library and archival materials are hygroscopic, readily absorbing and transferring moisture content. They respond quickly to seasonal changes in temperature and relative humidity by expanding and contracting, and these dimensional changes accelerate deterioration and lead to visible damage.

By incorporating a good DDC climate control system that can limit swings in temperature and humidity, historical material deterioration is kept to a minimum. A good HVAC System will normally include some type of desiccant dehumidification system, as well as a steam humidifier, dx or chilled water for cooling, a hydronic heating system, and air filtration designed for the application. Trying to achieve good temperature and humidity control with off-the-shelf HVAC equipment is a compromise, and one should consider the value of the materials being protected prior to making this type of decision.

A stable temperature of 65 to 72 °F and a stable relative humidity between 30% and 45% is a good guideline to start with, but also consider how the room is to be used. If the room is for only long-time storage, then colder temperatures may be better, but if the room is to be occupied then it may be more appropriate to increase the temperature. It is also important to give the material time to adjust to a new environment, if coming out of storage, to be used in another climate. To maintain constant temperatures and humidity, do not turn the HVAC off. Also, if the archival room is not occupied daily, remote alarming is essential.

Eliminating pollutants is very important to maintaining good air quality and extending the life of archival materials. There are usually two major types of pollutants, gases and particulates. Gaseous contaminants need to be understood and reviewed at each application, but ozone, sulfur dioxide, nitrogen oxides, and peroxides can be harmful and lead to the formation of acid in materials.

Our archival storage clients include:
  • L.L. Bean
  • New Orleans Historical Society
  • Maine Maritime Museum
  • Private libraries
  • Boat owners
  • Historic memorabilia collectors

Controlling air quality can be difficult, and it is best to involve an engineer that understands which gaseous contaminants and/or particulates need to be removed. Selection of the correct MERV rated filter is important, as is the use of activated carbon filtration at a minimum. This holds true for both air in the room as well as the air from outside, or the fresh ventilation air that you may be introducing to the room. It is also very important to have the foresight to take your outside air away from any potential contaminated areas, such as a roadside area, parking area, or loading dock area.

So, if we start with a well-designed space, we maintain good air quality, a stable temperature and humidity as stated above, perform a regular schedule of maintenance and filter replacement, and we monitor each space with good quality DDC controls, we will have reduced our risks, and given us every opportunity to have a successful installation.

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