Mold is everywhere--in the air, on surfaces, outdoors, indoors, on the cheese in our refrigerators. If it is all around us, why should we be concerned about mold in the library?

What to Do With Moldy Items
What to Do if There's a Mold Outbreak
Health Issues
UD Library Disaster Response Instructions for All Staff
UD Occupational Health and Safety Emergency Guide
A Brief Guide to Mold in the Workplace (OSHA)

Effect of Mold on Library Materials

Active mold produces enzymes that allow it to digest paper and cloth, which eventually weakens and destroys these materials. Inactive mold does not damage library materials, but the spores can be spread through the library if affected materials are handled, and will become active if environmental conditions are conducive to their growth. The musty odor of mold often remains in library materials even after mold has been inactivated and removed by vacuuming or wiping the mold off.

Active and Dormant Mold

Mold spores need a favorable environment to germinate, or become active, grow, and spread. The most important condition mold needs to germinate is moisture. Most molds will germinate at 65% relative humidity (RH). It is also possible, however, for some molds to grow at a lower RH. Higher temperatures and poor air circulation can accelerate mold growth. If collection materials get wet, they become more susceptible to mold growth. Water-damaged materials are at risk of mold growth while they remain wet, but they are also more susceptible to mold outbreaks later on, after they have been dried, if environmental conditions become favorable for growth.

It can sometimes be difficult to distinguish mold from dust, dirt, foxing, or cobwebs on collection materials. Mold can be almost any color. Mold usually has a recognizable musty odor, whether active or dormant. Active mold is soft and may smear easily, and it may be damp or slimy. Inactive mold is dry and powdery, and brushes off easily. Under magnification, it is easier to distinguish mold from dust and dirt. In the early stages of mold germination, it forms hair-like filaments in webs, then as it matures it develops a bushy appearance.

Preventing Mold Outbreaks

It is not possible to create an environment free of mold spores. Dormant spores are everywhere, therefore the only dependable way to avoid mold problems is to control the environment so that mold cannot become active. Control of the environment means maintaining moderate temperature and RH (never above 65%), good air circulation, keeping collections and collection storage areas clean, and not bringing new collection materials with mold into the library. It is also very important to keep books and other paper-based collections from getting wet, and to treat wet books as an emergency, since mold is likely to grow on such materials within 24 to 48 hours. Rook leaks and plumbing failures can result in library materials getting wet, so proper building maintenance is also necessary to avoid mold problems.

Procedures to Follow if Mold is Found in the Library

1) What to Do With Moldy Items

The first concern with mold-contaminated collection materials is health and safety. If you encounter a moldy collection item, avoid handling it. Either isolate the moldy material by putting it into a plastic bag, tie it closed, and bring it to the Preservation Department, or leave materials where they are and alert Preservation staff right away. If you are unpacking a box of gifts, for example, and it smells moldy or you see something that appears to be mold, close the box back up and move it to a location away from people, then contact the Preservation Department.

The Preservation Department is equipped to review individual, mold-contaminated materials. Adequate protection includes wearing a properly fitted respirator with HEPA (high efficiency particulate air) filters, disposable plastic gloves, and eye protection. Once materials are in the Preservation Department, staff can examine them safely in a self-contained fume hood. The air flow is drawn away from the worker via an exhaust mechanism fitted with a HEPA filter, which traps the mold particles.

2) What To Do If There's A Mold Outbreak

The first concern with a mold outbreak is health and safety. If there is a mold outbreak in the library (affecting a whole area of the building or collection) such as could occur following a water disaster, or a failure in the HVAC system that results in high temperature and high relative humidity, the first steps that need to be taken are to notify Occupational Health and Safety and close off the affected area so that staff and patrons cannot enter.

During the week days, notify Library Facilities (ext. 6940). On weekends and in the evening, notify Public Safety (911 or ext. 2222). Library Facilities or Public Safety will contact Occupational Health and Safety. After contacting Library Facilities or Public Safety, contact a member of the Disaster Coordinating Team.

The mold affected area should be closed off so that staff and patrons cannot enter. Doors should be closed, plastic sheeting hung to separate affected from unaffected parts of the collection. If possible, the air circulation should be reduced so that it does not flow from affected areas into unaffected areas.

After these first response steps are taken care of, the next concern is to:

Locate the source of high humidity. Likely causes are leaks from windows, roof, or pipes, or malfunctions in the heating and cooling systems (HVAC) that result in high RH. Problems can also develop within the HVAC system, due to a malfunction or lack of maintenance, and be spread through the building. Prime areas for mold problems to form are heat exchange coils, drip pans, and duct work.

Lower the humidity and increase the air circulation. The goal is to change the environmental conditions so that mold will be inactivated. Monitor the temperature and relative humidity regularly, and aim to get the RH below 50% and the temperature as low as possible, but at least down to 70 degrees F. Possible methods for reducing the RH and temperature are to lower the settings of the HVAC system, use fans to increase air flow, open windows if the air outside is colder and drier than indoors, or use dehumidifiers. Remove water-soaked items from the area, if present, such as ceiling tiles, upholstered furniture, and carpeting.

For more information on addressing mold problems, see Managing a Mold Invasion and Emergency Salvage of Moldy Books and Paper.

View the presentation on Mold in the Library (September 2004).

Retention of Mold-Affected Materials

In many cases, the best decision for mold-affected items in the general collection without artifactual value is to discard them. If their information content is important for the collection, finding replacements is often a better course of action than attempting to clean them. Rare and unique materials that have become moldy, however, usually are worth the cost and effort to clean. For potential gifts, only the most rare or scarce materials are worth the difficulties presented by mold. Cleaning moldy materials is time consuming and also carries some level of risk for staff who do this work. In addition, materials that were once moldy are always susceptible to future mold blooms to a greater extent than other materials, and must be stored in appropriate environmental conditions and monitored.

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