The Importance of Environmental Monitoring

Bonnie Parr, Abraham Lincoln Presidential Library and Museum

Providing a proper environment is fundamental to long-term preservation of library, archival, and cultural collections.  Paper-based items, photographic materials, and artifacts made of organic components are very reactive to the conditions around them.  In response to fluctuations in humidity, they expand and contract, resulting in dimensional changes.  They are vulnerable to mold growth, fading, and physical and chemical degradation caused by exposure to heat, moisture, and light.  To counteract these effects, it is important to stabilize temperature and humidity levels and to minimize exposure to light.  

Environmental monitoring is essential to gather information about and assess the effectiveness of the environment in which collections are kept.  To facilitate temperature and humidity monitoring, there are continuous recording devices (data loggers and hygrothermographs) and spot readers that display only current conditions (thermometers, hygrometers, and humidity indicator strips).  Light meters (used to measure visible light) and UV meters (used to measure ultra-violet radiation) take spot readings.  Blue Wool cards – which have strips of blue-dyed wool attached in a sequence from most light-sensitive to most light-stable dyes – provide visible evidence of light damage over a span of time.  By comparing cards exposed to light (the strips fade at different rates) with cards kept in the dark, it can be determined whether lighting in a specific location is appropriate or too strong for the storage or display of collection materials.  

Routine monitoring will catch problems early before they cause long-lasting damage.  Spikes in temperature or humidity detected by monitoring instruments are an indication that the HVAC equipment is malfunctioning or the monitored location is experiencing an unusual environmental influence.  A high lux/foot-candle reading on a light meter means that the light source is strong and likely to cause fading and other photochemical damage to sensitive items.  The quicker these issues are addressed the less likely collection materials will suffer long-term physical or chemical changes.

The records produced by monitoring the environment will provide a baseline of the existing conditions where collections are located.  They can be used to document daily and seasonal temperature and humidity ranges or identify areas with poor climate control.  Measuring ambient light conditions will help in assessing the suitability of lighting used or occurring in storage or display areas and the potential for damage caused by exposure to light.  

The records also can be used as supporting documentation for changes - adjusting climate control parameters to better meet the long-term preservation needs of the collection, planning for new or upgraded HVAC equipment, or improving collection storage and use practices.  Records of the collection environment are useful, and usually required, when applying for grants or other sources of funding for preservation projects. 

Managing a collection environment that provides stability and reduces risks for further deterioration is challenging.  It relies on careful monitoring to make sure climate control equipment is working properly, to identify problems requiring attention, to document conditions and their effects, and to support planning for improvements.  Environmental monitoring is a key tool in making informed decisions to ensure the longevity of collections.

Online Information Resources
 

American Institute for Conservation. AIC Wiki. “Environmental Guidelines.”

Connecting to Collections Care. Resources. (select) “Environmental Control.”

Conservation Center for Art and Historic Artifacts. “Collections Environment Infographic.”

Library of Congress Preservation Directorate. “The Deterioration and Preservation of Paper:  Some Essential Facts.”  

Northeast Document Conservation Center. “2.1 Temperature, Relative Humidity, Light and Air Quality:  Basic Guidelines for Preservation.”  

Northeast Document Conservation Center. “2.2 Monitoring Temperature and Relative Humidity.” 

Northeast Document Conservation Center.  “2.4 Protection from Light Damage.” 

Return to Communicating the Value of Preservation