The only way to prevent mold is by altering conditions conducive to its growth. For example, paper collections should not be stored in a basement with a low temperature, high humidity, little light, and very low air circulation—ideal conditions for the growth of mold. Even if remedial treatment is undertaken, the material will quickly deteriorate again if returned to the environment in which the mold first developed.

When the cause has been traced, take immediate steps to remove it. Vacuum or mop up standing water, adjust the HVAC, and/or activate electric fans to speed up the circulation of air. If dehumidifiers are available, they should be employed with both HVAC and fans.

Mold is the prime enemy of film materials, attacking the surface and emulsion. If film is unprocessed and in a moisture-proof container, it is usually safe from mold. However, when the package is broken, mold threads or filaments develop and immediately become apparent when the film is exposed. Film left in a camera in humid conditions is especially susceptible to mold. Coating microfilm during processing is regarded as a useful preventive measure, as this reduces the risk to the emulsion layer and allows the mold to be removed before serious damage occurs. One such coating is polysulfide, developed by the Image Permanence Institute of Rochester, New York (USA) (see Reformatting).