Mold is a fungi which reproduces by spores and is found everywhere. They also contain carbon. Mildew is just a form of mold. All substrates can support mold, both inside and outside our bodies. Molds can be very beneficial…and also tasty (think Brie).
As mold grows, it releases enzymes and toxins and it actually digests the substrate it is on. Spores form and become airborne and are very hard to kill. When a spore matures, it is released and has everything it needs to form a new colony. It just needs the right conditions to become active. Inactive mold is hard to remove, but active mold can be easily removed. Good air circulation is very important for preventing mold growth. “Foxing” is a form of mold growth which causes permanent stains in a book, probably is caused by mold introduced when the paper was made. Mold spores cannot be eliminated in the air.
Mold growth on library materials is permanent. Isopropyl alcohol is best as a treatment for inactive mold spores on books. Active mold spores can cause health problems, especially for individuals with low immune function. In order to keep mold out of our collections, we should keep a low relative humidity (40-50 %) and have good air circulation. We should try to keep dust off of our library materials as well. Gift materials should be examined carefully for mold growth. In order to remove mold, one should use gloves, an air respirator and goggles. You should isolate any mold-affected areas, and quarantine the area with plastic if you can. To deactivate the mold growth in an area, you should lower the humidity and allow areas to dry. Inactive mold looks like dust and can then be removed by vacuuming with a HEPA filtered vacuum and wiping with a dry-cleaning sponge. The shelving the affected books were on should then be cleaned with bleach. The environment should then be monitored to make sure mold growth dies not return. Any severely affected books or materials should be discarded.
Mold can develop in as little as 48 hours and should be treated as a health hazard. There is no one chemical that will kill all mold, but alcohol will kill most molds.
Source: Invasion of the Giant Mold spore