Mold is constantly present in the air and on most objects. It is most evident in locations where there is a high relative humidity or when there has been water damage. Its presence, particularly the smell, is sometimes masked by odors of wet items, such as acoustic tiles.
Mold should be treated seriously. It is highly in- fectious and will spread throughout furnishings, materials, and the building. Mold will irritate peo- ple who have allergies and asthma.
Mold and mildew will grow between 40° and 100° Fahrenheit when conditions are right. Mold likes a moist environment and the dark, as seen by mold in a refrigerator or basement.
Different types of mold like to grow on different materials. Some like trees and wood; others like leather or the glues and starch found in books; and others like gelatin and paper pulp. In most instances, a variety of mold species will be visible on a “moldy”
object. Three major types of mold are found in build- ings: allergenic, mycotic, and toxic. Most tests will reveal allergenic mold varieties. An example of my- cotic mold is Candida. A toxic variety of mold is Stachybotrys chartarum also known as Stachybotrys atra.This type of toxic mold has been in the head- lines for the past few years.
Allergenic mold will trigger allergies and asthma.
Coughing, sneezing, and discomfort are the most common symptoms. People working around mold, especially those with allergies, should protect them- selves by wearing respirators, gloves, and disposable or washable clothing.
Working around mold can cause people to de- velop sensitivities and then allergies to the mold.
Therefore, health and safety precautions are ad- vised for all employees. In addition, all air in areas where moldy materials are stored or being cleaned
should be vented to the outside. Air-handling sys- tems should not be recycling this moldy air.
The presence of Stachybotrys atrais a sign that there is excess moisture or water within the build- ing. It is sometimes found behind walls, sometimes in mechanical and HVAC rooms. Stachybotrys atra loves materials that are high in cellulose and it re- quires high humidity to grow. Not all black molds are Stachybotrys atra. If you do find Stachybotrys atra,consult with an industrial hygienist about test- ing and removal of the active mold. The source of the excess moisture should be identified and elimi- nated prior to initiating the removal of the mold from the building. Removing the mold without elim- inating the excess moisture is pointless; the mold will just return.7
Control of the environment and moisture are key factors in dealing with and controlling mold.
High relative humidity and hygroscopic materials will encourage mold growth. Hygroscopic materials include furniture, carpets, works of art on canvas and paper, textiles, acoustic tiles, paper, books, and wood. Moisture barriers are not always useful for controlling mold, for they may not let the moisture out, therefore allowing mold to grow. Examples of moisture barriers are vinyl paint, wall coverings, and plastic sheeting. The moisture condenses on the cooler side and encourages mold growth.
Effects of Mold
Cellulose or Paper-Based Materials
Mold eats away at cellulose materials, weakening the fibers and destroying the form. Paper becomes stained. Books will swell in areas where mold has infected them. Mold is attracted by an increased moisture content. Normal moisture content of pa- per should be between 6 percent and 8 percent. Be- low this, paper becomes brittle. Above 8 percent, paper is too wet and encourages mold to grow. Mold will grow on all areas of books and papers. Different species or varieties of mold are attracted to starch, adhesives, cellulose, leather, or cloth. Different col- ors and textures of mold indicate different species.
The goal of removing and “eliminating” mold is to keep it from germinating and thereby infecting
the entire collection or building. Controlling the environment and eliminating sources of “food” will inhibit mold growth.
Film-Based Materials
Mold is attracted to film-based materials such as photographs, negatives, microfilm/microfiche, and motion picture film. The mold will grow on the sur- face of photographs, etc., eating away the images.
To prevent mold growth, keep the rH below 50 percent. If mold starts to grow, clean off and store items under low rH conditions.
Mold also likes fingerprints and body oils and salts. Avoid touching photographs and negatives with bare hands. The mold will grow in traces of fingerprints and continue to damage the photo- graph surfaces.
If mold infects slides, remove them from mounts before drying and cleaning. Replace the mounts when the slides dry.
A method to prevent mold growth on film-based materials is to store them in frost-free refrigerators.
Eliminate all sources of condensation in the refrig- erator, or mold will grow without control. Store in low temperatures and rH. Use dehumidification if necessary.
The following are ideal temperature and rela- tive humidity ranges for the storage of film-based materials:
Black-and-white film:50° to 70° Fahrenheit (± 2°); 20 percent to 30 percent relative humidity, with a maximum of 50 per- cent relative humidity
Color film:15° to 35° Fahrenheit (± 2°); 20 percent to 30 percent relative humidity, with a maximum of 50 percent relative humidity
Magnetic or Tape-Based Materials
Mold will infect magnetic and tape-based materials also. The mold is attracted to the binder or adhesive that attaches the layers of tape together. A white sticky residue is a sign of mold infection. Store magnetic and tape-based media in a low rH envi- ronment to prevent mold growth. Mold should be
removed by professional tape restoration firms to prevent loss of image, sound, or information.
Controlling Mold
To control additional growth in a building and on a collection, determine what caused the mold.
• Check the temperature and relative humid- ity. The temperature should be below 72° Fahr- enheit, preferably below 70° Fahrenheit. The relative humidity should be below 60 percent;
the ideal rH is 45 percent to 50 percent.
• Dark, moist areas are prime locations for mold growth. Turning on the lights can slow growth.
• Check air circulation. Stagnant air and moist conditions will also trigger mold growth.
• Check intake, heating, and cooling ducts for obstructions to air flow.
• Check heating-exchange coils. This is a prime location for mold growth. Mold on the coils will spread throughout a building via the ductwork. Clean coils with disinfectant.
• Check air ducts. Clean any infected ducts. A fungicide or microbial cleanser can be used under controlled conditions, with approval by a conservation or preservation officer.
• Fix or eliminate the mold problem at the source. Treating only the symptoms guaran- tees another infection of mold.
• Isolate the infected materials in a room or area. Ventilate air to the outside to prevent spreading mold into the air ducts.
Change the Environment
• Increase air circulation and decrease humidity.
• Dehumidification is the best method. Opening windows if the rH is lower outside is a possibility.
• Measure the relative humidity using a hygrograph.
Measurements should be taken several times a day. A hygrograph is the best instrument because it records temperature and rH over a period of one week or month and will provide justification for fixing serious environmental problems in a building.
Remove mold from books and objects. Vent all the air to the outside, both in the area with the mold infection and where you are removing mold.
Clean and disinfect the room, shelves, and any wood or metal containers. Use Lysol, Clorox, or a disinfectant. Try not to reinfect air ducts. Use pro- tective clothing, gloves, and respirators when clean- ing. Clean all clothing after exposure to mold.
Odors can be removed by opening baking soda or placing charcoal in the room. Do not use these items directly on books!
Ozone is not suitable for eradication or control of mold because of its side effects and unpredictabil- ity. See the materials on ozone, later in this section.
Cleaning Dirty and Moldy Books
Dry all materials before cleaning. Moldy materials that cannot be treated immediately should be frozen.
Freezing mold does not kill or eradicate it but merely stops mold growth. Take the following six steps to clean dirty and moldy books.
1. Hold book shut at front edge.
2. Vacuum mold from
• top edge of book, moving from spine to edge;
• bottom edge from spine to edge; and
• front edge from top to bottom.
3. Vacuum
• front cover,
• back cover, and
• spine.
4. Open front cover.
• vacuum inner edge near fold (hinge area).
5. Open back cover.
• vacuum inner edge near fold (hinge area).
6. Repeat the process using a “dry chemical sponge.”
Dry chemical sponges are made of pure latex or rubber, not cellulose.Do not get dry chemical sponges wet. Do not use any liquid to eliminate mold; it will cause mold to grow again. Do not put treated mate- rials into sealed containers, boxes, or plastic; this can encourage mold growth.
Before returning cleaned materials to the regu- lar collection, take the following steps:
• Look through the books and make certain no mold, soot, and dirt remains.
• Put books in a stable, dry environment.
• Monitor books for reappearance of mold.
• Return books to their original location after the environment is stable and the relative humidity is back to 45 percent to 60 percent (± 2 percent). These materials are very sus- ceptible to mold.
• Monitor previously infected areas through- out seasonal changes to determine that mold remains arrested.
Mold in Buildings
A major cause of sick building syndrome is the pres- ence of mold in the HVAC system. The mold is car- ried throughout the structure by the fans blowing air across a moldy condensation coil, heat exchange coil, or even moldy ducts. This contaminated air is recirculated again and again until it becomes a se- rious health issue.
External walls and joints contribute to mold growth. The moisture condenses near these cooler walls and can encourage the growth of mold. Keep- ing air flow active and increasing the temperature of the air near these external surfaces can control mold. Decreasing the moisture content of the air is also important.
Poor environmental conditions are perfect for encouraging mold growth. When a building is air- conditioned, there is a good chance for mold. Just because there is air-conditioning does not mean that there is humidity control. If the air-conditioning is up too high, surfaces can become too cold and the moisture content too high. At this point, water will condense on the surfaces and encourage mold growth.
To prevent this, decrease the number of “cold” spots by increasing the air flow and the temperature.
Condensation on windowsis a key indicator of an imbalance in the environment. Conditions are ripe for a mold infection.
Check air ducts, heating and cooling ducts, and intake ducts to make certain air flow is not obstructed.
Treat the cause andthe symptoms, not just the symptoms, of poor indoor air quality.
• Clean all infected areas.
• Eliminate outside and building factors that encourage mold or condensation.
• Stabilize the environment.
• Monitor areas for reinfection.