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What is mold, and how does it become a problem?

Mold is a type of fungus that appears on the surface of organic materials in damp conditions. Molds may be gray, black, green, yellow, orange or various other colors, and individuals with specific allergic conditions may have a significant reaction to air-borne mold spores. Both indoor and outdoor mold and fungus have been shown to represent a huge allergy problem for many individuals. There are three primary factors always associated with mold growth - temperature, nutrients, and moisture. Mold and fungus need humid conditions in order to live and grow.

Most molds must get their nutrients (food) from the environment, living and feeding on dead organic matter. Outdoors, molds are very important in nature, as they aid in decomposing organic materials and recycling nutrients. Indoors, many building components and contents contain materials that are excellent food sources for mold, such as wallpaper glue, some paints, greases, paper, textiles, wood, and wood products. Indoor dusts may contain fibers, dead skin cells, and other organic matter that can serve as a food source for mold when adequate moisture (greater than 15%) is available. Mold can grow on concrete or stone when sufficient organic matter is present to promote growth.

Temperature also affects mold growth. Different types of mold have minimum, ideal and maximum temperature ranges for growth. Most molds grow well at temperatures between 60 - 80 degrees F, which represents normal indoor temperatures. The following table describes ideal conditions for indoor mold growth:

Factor Range Comments
Temperature 60-80 F Some molds can survive at colder or warmer temperatures
Relative Humidity >60% Measurement of amount of water in air compared to the amount of water that the air can hold
Moisture >15% Moisture greater than 20% almost guarantees mold conditions

Mold Treatment

The best way to eliminate mold is to eliminate mold growth conditions. Proper ventilation can help considerably; a dehumidifier, fans, and/or air conditioner will generally reduce moisture levels. Spraying with a oxidizing solution such as household bleach may kill mold, but it will not eliminate mold conditions for long. It is important to note that while disinfectants and biocides may kill mold spores and take away their ability to reproduce, these products should not be used alone in addressing a mold problem. Either the mold must be completely removed from the affected material, or the mold-contaminated material must be completely removed from the building. Airborne spores are often present, and can resettle on treated surfaces if mold conditions are still present.

When deciding which materials can be treated and which should be removed, the important factors are how porous (absorbent) the material is and the degree of mold growth. If material is completely permeated (wet carpet, upholstery, drapes, ceiling tiles, wallboard, paneling, etc.) it must be removed. It may be extremely difficult to completely remove or treat mold from these materials successfully. Generally, non-porous materials ( metals, glass and plastics) and semi-porous materials (wood, plaster and concrete) that are visibly moldy but structurally sound can be successfully treated.

Cleanup and mold removal activities can expose people to mold particles and other hazards, so it is important to wear protective equipment and follow safety procedures. Large projects require careful planning and implementation to be safely and effectively productive.

If mold conditions persist after treatment, it is because the conditions for mold growth have not been eliminated! Regular inspection of problem areas is a key to preventing mold recurrence.