Connecticut State Library with state seal

Preservation Office

Preservation Advice for Libraries, Historical Societies and Home Collections:
The Storage Environment


Damage from light can occur to art and photographs displayed on the wall, to books on a book shelf near a sunny window and, over time, to any object exposed to natural or artificial light. Some materials are more sensitive to light damage than others but any exposure to light eventually adds up to damage. Be careful when using, storing and displaying your valuable materials.

Damage from light is cumulative and irreversible. That means that high light levels cause damage quickly but low light levels for long periods will eventually cause the same amount of damage. The damage is permanent; ink can’t be restored to its original legibility and paper can’t be made stronger.

Ultraviolet is the most damaging but all forms of light cause damage by providing the energy for the chemical reactions that cause deterioration. UV filters wear out in about ten years. If you currently display materials protected with a UV filter, the manufacturer should have provided information on how long the filters would be effective. Establish a maintenance schedule to replace or recoat the glass or filters when needed.

More information:

Additional technical notes, 1:15 Light exposure guide for the display of museum objects, from the Harpers Ferry Center, National Park Service, U.S. Dept. of the Interior, last updated Jan. 9, 2009.

Colby, Karen M. “A suggested exhibition policy for works of art on paper” Journal of the International Institute for Conservation – Canadian Group, Vol. 17 (1997) p. 3-11. Various types of art works are grouped by sensitivity to light. Category 1, the most sensitive, includes most color photographs and many other kinds of art works. Category 2, medium sensitivity includes materials such as wood pup paper which is used to make newspapers and many books and documents produced in the 20th-century. But, even Category 3 materials, which includes good quality rag papers, are limited to 20 weeks of exhibition at the low light levels used in museums.

Environmental conditions for exhibiting library and archival materials by The National Information Standards Organization. Search by "designation" Z39.79.

Protection from light damage by Beth Lindblom Patkus from NEDCC discusses how to determine how much light is too much for an exhibit area, how to measure light levels and estimate light damage (some items are more sensitive than others) and how to control the light in an exhibit area.


The most important step to increase the longevity of your materials and to prevent mold outbreaks or pest damage is to control the temperature and the relative humidity. In fact, recent research shows that controlling the humidity is more important than controlling the temperature. For books, the recommendation is to keep the relative humidity below 50% and the temperature below 70 degrees Fahrenheit. This is difficult and expensive in the average library, home or office so do the best you can by providing a clean storage space that has no leaking pipes or moisture seeping through a crack and by circulating the air.

Typical building HVAC systems and home air conditioners control temperature fairly well but do not control humidity except as a byproduct of the temperature control. When the required temperature is achieved, the equipment stops running. But outdoor relative humidity can penetrate a cooled room in a very short time. Also, if you turn off the AC when not at home, the room gets hot and humid, then you come in, turn on the AC and the room gets cool and dry. Then you leave and the room gets hot and humid again. This constant cycle of hot and humid vs. cool and dry is more damaging than putting the materials in a room that stays hot and humid.

Try to answer these questions. Does the HVAC turn off before the relative humidity is sufficiently lowered and does it stay off long after the relative humidity rises? Is the thermostat programmed for a higher temperature at night or on weekends? Is the system turned off over the weekend? If the power goes out, will the air conditioners and other equipment come back on automatically or does a breaker have to be reset? Whose job is it to reset the breaker if there's a power outage after hours on the Friday of the three-day July 4th weekend?

Equipment exists that will control the relative humidity better than the typical HVAC system but it will be expensive to determine what is the right equipment (hire a consultant), expensive to install (hire a HVAC contractor who specializes in such equipment and purchase the equipment), expensive to run (budget for electrical costs) and expensive to maintain (train your facilities staff and/or get a maintenance contract).

Get a device called a datalogger and use it to monitor the temperature and relative humidity. Some vendors sell temperature/relative humidity indicator cards that will give you a rough idea of conditions in various areas of your building. Keep a spreadsheet or other report of the results. Do tests in various parts of the building and compare the results.

Mold and pests prefer undisturbed, dusty or dirty, moist and dark areas. Helpful strategies include housekeeping, keeping the air circulating at all times (as with fans) and judiciously leaving the lights on so there are no dank or airless areas.

Think about whether your valuable books and materials are stored in the basement or top floor. Perhaps the most valuable (the ones you want to keep the longest or that have collectible or monetary value) should be moved to a part of the building where the temperature and relative humidity are more under control (monitor the environment to determine where this is).

More information:

Low-cost/no-cost improvements in climate control by NEDCC.

Monitoring temperature and relative humidity by Beth Lindblom Patkus for NEDCC

More easy environmental monitoring: dataloggers by Michael Barford. In Abbey Newsletter v.15:no.7 Nov. 1991.

Step-by-step workbook: achieving a preservation environment for collections by the Image Permanence Institute at Rochester Institute of Technology

The archives of the electronic discussion list Conservation DistList will have recent exchanges about dataloggers and other topics. Search by keyword.


A library, historical society, museum or town clerk’s office might wish to hire a consultant to make recommendations on how to control the environment and other preservation needs of the collection. A general preservation survey will give an institution information on the overall condition of the building and collections.

More information:

Assessing Preservation Needs : A Self-Survey Guide [by] Beth Patkus. Andover, Mass. : NEDCC, 2003.

Grant sources from NEDCC. Choose from the list for information on federal, state, and private sources of funding for help in paying for a preservation survey. This list is kept up-to-date with information on such programs as Heritage Preservation’s Conservation Assessment Program (CAP) grants and the National Endowment for the Humanities’ Preservation Assistance Grants – For Smaller Institutions, both of which target specific types of institutions to have a consultant do a general preservation survey.

Needs Assessment Survey by Sherelyn Ogden, from NEDCC

Preservation Assessment and Planning from NEDCC

Suppliers List by NEDCC including Preservation Consultants and Environmental Engineering and Design services.


The simple, common sense activity of keeping your collections and storage areas clean has a large impact on preserving your materials. Eliminating dust and debris reduces the risk of a mold outbreak or pest infestation and cuts down on wear and tear through abrasion by scratchy dust particles. Have a daily, weekly and monthly schedule for cleaning your collections and the storage area. Plan to periodically clean under and behind furniture.

Remove dust from shelves with cloths that hold a static charge so the dust doesn’t settle back on your materials. If using wet or damp cloths or mops, make sure the moisture completely and quickly evaporates before putting items back on a shelf. Be cautious about wet cleaning of any valuable object. Be cautious as well before using any kind of cleaning solution or polish.

Use a HEPA vacuum with variable suction and a brush attachment on books. For delicate items, work by hand, use a soft brush and work outdoors or hold the item near a running vacuum which will capture the dust that you remove. Hold the book by the spine with the fore-edge parallel to the floor and brush away from the spine towards the floor.

More information:

Librarian’s facility management handbook by Carmine J. Trotta and Marcia Trotta. New York : Neal Schuman, c2001.

Managing a stacks cleaning project” by Shannon Zachary. In Archival Products news v.5:no.1 1997:winter p.1-2,5.

Preservation 101, 5, Collections Care, Exploring Collections Maintenance Housekeeping from NEDCC.

Request for proposal for cleaning volumes and stacks of Sterling Memorial Library” Yale University Library. Preservation Department. 2005:July 18


When moving to a new building or transporting books from one library to another, consider how to protect books and other materials during transport. Use packing material to cushion books packed in boxes. Load book trucks so books are supported by a book end that won’t slip or are packed reasonably tight so books won’t fall off. Consider cleaning each volume before packing it.

Commercial companies can help during a major move but seek a company that specializes in moving library collections: a company used to moving furniture and office paper may not understand the importance of protecting books of varying height, shape and thickness or of keeping them in order.

If moving rare or special collection materials consider additional precautions. Find out what your insurance covers. One rare book library discovered that the maximum their insurance would pay per truck load was about the same as the value of just one of their Audubon portfolios, so, for that expensive set of books, the truck made one trip per book.

More information:

“Helpful hints for the safe transport of library materials” by Oliver Cutshaw. Go to p.4-5 in Archival Products news v.9:no.3 [no date, 2002?] Describes procedures and guidelines used by Harvard University for the proper care of materials in transit between off-site storage and libraries.

“The moving of collections” by Alfred E. Lemmon. p. 40-45 in Under Construction: Preservation Issues During Building Projects and Renovations Proceedings from a SOLINET Preservation Conference, SOLINET Annual Membership Meeting, Atlanta, GA, May 30, 2003. Click on “Under construction, all pages.” Also available as a self-paced or online class: search for the phrase "Under Construction" at the LYRASIS site.


If you are planning a new building or addition, keep the preservation concerns of your collections in mind. The architect and designer should incorporate such things as no windows in collection storage areas, no plumbing above collection storage areas (except fire suppression systems) and an unobstructed view from the reference desk to hinder anyone who might deliberately or inadvertently damage the local history or special collections.

During renovation and construction, books and library materials are subjected to the risk of a burst pipe or a fire. In fact construction is the second most common cause of library fires (arson is the first). Dust and particles from construction or renovation can get all over a building and can act like sandpaper, wearing away at your materials. Workers can go, unsupervised, all over the building, and this may require unlocking security doors. This leaves your collections vulnerable to vandalism and theft.

“Selection of a contractor should include an evaluation of safety and loss records on projects of similar scope.” (p. 362) From: Ch. 13 “Fire precautions during construction” Fire safe building rehabilitation by John M. Watts, Jr. [and] Marilyn E. Kaplan, Quincy, Mass. : National Fire Protection Association, c2003.

For public libraries in the state, the Connecticut State Library offers a library construction grant program and has a consultant who can advise you about library building and renovation projects. Go the Division of Library Development’s “Library Buildings and Construction.”

See also the Connecticut State Library’s “Library Space Planning Guide.” 

More information:

“Fire precautions during construction” Fire safe building rehabilitation by John M. Watts, Jr. [and] Marilyn E. Kaplan, Quincy, Mass. : National Fire Protection Association, c2003.

"Preservation Concerns in Building Design: a Bibliography" from NEDCC.

Preservation Concerns in Construction and Remodeling of Libraries: Planning for Preservation. Michael Trinkley. Columbia, SC: South Carolina State Library, 1992.

Protecting collections during renovation by Karen Motylewski from NEDCC.

Under Construction: Preservation Issues During Building Projects and Renovations Proceedings from a SOLINET Preservation Conference, SOLINET Annual Membership Meeting, Atlanta, GA, May 30, 2003. Click on “Under construction, all pages.” Also available as a self-paced or online class: search for the phrase "Under Construction" at the LYRASIS site.


Prepared by Connecticut State Library Preservation Office staff; last updated Nov. 2011.