The Abbey Newsletter

Volume 15, Number 7
Nov 1991

A New Approach to Treating Fungus in Small Libraries

by William R. Chamberlain
Director, General Library Division,
Virginia State Library and Archives,
11th Street at Capitol Square,
Richmond VA 23219-3491 (804/786-2332)

Reprinted with permission, in revised and updated from Biodeterioration Research 1, edited by Gerald C. Llewellyn and Charles E. O'Rear. New York and London: Plenum Press, 1988. Pp. 323-327.

In 1984 Dennis Allsopp, Director of the Biodeterioration Centre at Kew in London, in an address to the British Society of Archivists, started by commenting that the majority of library and archival conservators have no training in microbiology. He closed his remarks by saying, "My final advice is that you should find your local microbiologist and interest him in the potential problem before it occurs." I hope that what I have to report will enlist help with problems that have occurred and continue to occur.

The traditional approach in the library world to the problem of fungus is to control temperature and humidity to a level that discourages growth. If a book is brought in to the library with fungus or is found in the collection, it can be treated with chemicals that do not damage the paper. The literature indicates that a library will have no further concern with fungus. This sounds ideal, unless you have no air conditioning, or like the Virginia State Library, your air conditioning units are so old that they start to malfunction. When this happens, an outbreak occurs and then the problem becomes how to treat many books for mold growth. We estimated in 1978 that we probably had a minimum of 5,000 volumes infected. We also found, through the kind services of the State Laboratory, that the whole building contained fungal spores in every area where samples were collected, although the spore counts were not unusually high. Eighteen species of fungus were identified.

At the same time we began to receive requests for help from small libraries and private collections, ranging in size from 2,000 to about 20,000 volumes. In every case these collections were maintained in older homes or buildings and fungal growth was already present. There was also no air conditioning in any of the buildings and no intention of installing it. In addition, there was no extra funding available and seldom any extra manpower.

It became obvious that there were two problems to be addressed: (1) the damage to the books, and (2) how to stop and/or minimize the danger of the fungus outbreak recurring. Also, an overriding consideration was to reduce the health-related risks to staff or residents.

Factors in the Epidemic

In our efforts at the State Library we had identified six major factors to be addressed in attempting to halt the epidemic. They are listed below:

  1. Identify the pattern of growth shown by the fungus. It was very apparent that different species of fungi had different patterns. Some liked buckram bindings, some liked leather. One species appeared light tolerant and attacked the spines of the books. Yet another species would only grow on the paper in the darkest spots. Once a pattern had been established it became easier to identify possible trouble areas in the building.

  2. The airborne spread of the fungus. In most library literature the fact that fungi are spread by airborne spores has gone unnoticed. Watching for air drafts and pockets of dead air was a guide to problem areas or potential deposits of spores.

  3. Spores in the dust. As a corollary it has become automatic to check for areas where dust builds up regularly. We pay particular attention to window sills, comers, stairs and air vents.

  4. Special danger areas in the shelving of books. One area that is often overlooked as a source of trouble is that behind the books where it is dark, warm, and often humid with virtually no air circulation, i.e., ideal for fungi. We also paid particular attention to those shelves that were against the "weather wall" (i.e., the wall against which the prevailing wind consistently blew the rain, or the southwest wall in Richmond). The probability of high moisture content in the wall, and therefore in the books, is greatest here.

  5. Reaction to light. The majority of fungal species that attack books appear to dislike light. Even the few that grow on the spines appear to slow down in direct relation to the amount of light

  6. Classification of book damage. We very soon realized that damaged books fall into four categories. These are listed below:
    A. Minor, stained but still usable.
    B. Rebind; outer covers badly damaged but contents acceptable.
    C. Important works for which everything must be done to preserve the book as a whole.
    D. Discard; those too badly damaged or those for which buying a replacement is cheaper than rebinding or repairing.

Control of the Outbreak

With these factors in mind we were ready to work out a procedure to recommend. Again it is important to remember that our advice was only sought after fungi had already been found.

Step l. Open windows and install the largest available fan to exhaust air out of the room or rooms. The intent of this was to try to remove spores from the area before they had a chance to settle and begin new growth or pose a health hazard. It is important to try to locate the fan where it will draw from the largest area. This appears to be very effective in controlling the spread, and we have used it successfully, but it has not been scientifically tested.

Step 2 . Try to establish the pattern of the outbreak and obtain an estimate of the number of books affected. As an appropriate cross check we have found that the presence of mold can be detected by smell in small areas where up to 10% of the total number of volumes are affected. (Obviously, this is not an invariable proportion.) The stronger the smell, the greater the percentage affected.

Step 3. Once the number has been estimated, a work place must be set aside, and all the damaged books moved there. They should be standing up and open to the light and circulating air. The size of the area depends on the number of books. The ideal is to set up tables outside in the sun. Next best is a well-ventilated room with plenty of light. The problem is to balance drying the fungi and the books, on the one hand, against the damage that light can do to paper on the other. The maximum time in the sun should be something less than six hours, depending on the quality of paper. Newsprint, for example, can only take about one hour of direct sunlight before serious damage starts.

Step 4. Vacuum the whole area carefully to remove dust, paying special attention to backs of shelves and comers or joints of the floor and furniture. We estimate that 30-50% of mold spores are captured by this initial step. Although individual spores are small enough to pass through the vacuum cleaner bag, many of them ride on dust particles, which are retained.

Step 5. Disinfect the area. Using a wet cloth or mop and a strong household disinfectant, preferably with a fungicide in it (like Lysol or other bathroom fungus removers), clean all areas, especially those shelves that have had fungi present.

Step 6. While allowing the area to dry thoroughly, sort and inspect the books and clean those books that will be returned to the shelf. A power vacuum with a soft brush can replace the hand-held brush, but care must be taken with either method to clean the books systematically in order not to transfer spores from one book to another. With a vacuum, a piece of cheesecloth should be placed over the nozzle and replaced regularly to reduce cross-contamination. This also helps keep fragments of the book from being drawn into the machine and effectively lost.

Step 7 Reshelve books that are to be kept, discarding those that are too damaged, and arrange to have special attention paid to those that need it.

Step 8 Start planning some kind of regular cleaning and preventative process. This should include disinfecting by mopping at least once a year. Every book should be taken off the shelf and both book and shelf vacuumed at least once a year. If possible, a window fan should be installed if an air conditioner can not be bought. At the very least, windows must be opened regularly.

The above is a practical approach to the problems and as such is recommended to librarians. Library literature does not tell us how to successfully combat a major fungal problem. Our procedure raised several questions, of which the most important one is "Does it work?" I have heard that this has been tested by the Smithsonian and we feel that it does work. Our eight-part control program, set up following the 1978 outbreak, proved its worth in 1987, when the State Library was closed for three months beginning in September, and without power for 6 weeks of that period. There was no serious outbreak of fungus in the General Library Collection during those three months. This seems to mean that we reduced the odds of a similar serious outbreak and that the program works for prevention as well as control of active fungal growth.

The Need for Further Research and Exploration

We still need to do more testing on what really works. We need more information as to why one library is hit with fungus and another is not, and what changes occur before an outbreak occurs. Some of the cases at the State Library would indicate that temperature is more important than humidity, but we need more work on the moisture content of books in relation to air humidity and the presence of fungi. We believe that the moisture content of a book can increase to a level that will support fungus growth before the relative humidity in the air exceeds the traditional 60% or 65% limit of safety, as a result of moisture from the metabolism of xerophyllic fungi.

The problem with the microclimate created between the fore-edges of the books and the walls or central stack area must also be addressed. We have been using slatted shelves in many areas of the library, which allow increased movement of air, with good results. What should we do, though, where solid shelves are used and where lack of space gives us no choice but to shelve against an outside wall? I am currently recommending that wooden shelves should be cut down where possible to increase air space, and that a sealant be used on damp areas of adjacent walls, but again this has not been tested to see if the sealant might be harmful to the books.

Since mold spreads through airborne spores, is there a more efficient way to attack these spores? Would electrostatic precipitators and smoke removers be effective in abstracting the spores and destroying them? How many and what size would be needed for an average library? Is it a waste of time to try to remove them from the air? Recent rumors of a heat incinerating precipitator are very interesting since the only way to destroy spores is by heating them over 160 degrees, or exposing them to radiation or certain fungicidal Bases.

What is the best and quickest way of removing fungi from the books without harming the books or the people doing the work? When the numbers affected are small, then the treatment is easy. When one faces more than 5,000 books, washing or other treatment becomes much more of a major undertaking.

Is it really necessary to remove the books from the shelves for cleaning, repeatedly and on a continuing basis? If the first cleaning works, what is a realistic time frame for subsequent cleanings? At the State Library we used to attempt this cleaning only in our Rare Book Room, and each shelving unit was cleaned about twice a year. We have had no Fungus growth there, in spite of spores found in the dust, and problems with lighting and humidity. We have now cleaned all shelves in the general collections, and twice a year we damp mop the floors and stairs with a household disinfectant (generally Lysol). This is done in November and again in April, when the relative humidity is lowest in the building, and the cleaning is less likely to increase humidity to a dangerous level.

For those libraries that circulate books, there is one more thought. What happens when a patron returns a book that has been sitting in a hot car during a thunderstorm? We have had some books returned that feel as if they can be wrung out. If they are placed immediately on the shelves, then the moisture will migrate into the books next to them. For the moment, we routinely place all books on book trucks and do not shelve them for at least 14 hours, to give them a chance to dry out. It also gives us the chance to review the books for permanent damage. Books not dry by morning are not shelved.

Finally, what are the medical dangers inherent in fungus in libraries? We at the library have one proven case in which a staff member was diagnosed as having an infection from Aspergillus niger, one of the species of fungus present in the library. Other staff members have had skin disorders that could have been caused by fungi, and one staff member can not work in the stacks without a mask and goggles. There is a general belief here that our rate of absenteeism for respiratory problems, though lower now than it was before the control program, is higher than the average for other state agencies. Again, this aspect has not been systematically studied.


Allsopp, D. (1985). Biology and growth requirements of moulds and other deteriogenic fungi. J. Soc. Archivists, 7, 530-533.

Banks, P. M. (1974). Environmental standards for storage of books and manuscripts. Lib. J., 99, 339.

Chamberlain, W. R. (1982). Fungus in the Library. Lib. & Arch. Security, 4, 35-55.

Cunha, G. D. M. (1967). Conservation of Library Materials. Metuchen, N.J.: Scarecrow Press.

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