First, one must understand how mold lives. Many molds need simple things to exist and colonize. Most require a type of moist intrusion or humidity, otherwise known as "the wicking effect. " In some cases, it can take as little as 24 hours for this process to begin. After the source of the moisture has stopped, it does not mean that the mold has stopped growing.

Some molds are cryophytes (these adapt to low temperatures), some are thermo tolerant (they adapt to a wide range of temperatures) and some are thermophiles (they adapt to high temperatures). Depending on the species, these microbes will grow just about anywhere. Mold requires a compatible temperature for each species. Environmental factors (temperature, nitrogen, oxygen, etc. ) are necessary compounds for indoor molds to thrive.

Mold also needs an organic source of food. People might be confused as mold can grow on glass, tile, stainless steel, cookware, etc., but it is generally feeding off of some organic source deposited on this material (oils, film, dirt, skin cells, etc. ). The fiberglass insulation people like to say that mold does not grow on their product which is a fairly true statement, however, it grows on the organic debris that become trapped in their products. Mold also grows on things such as wood, fabric, leather, gypsum, fiberboard, drywall, stucco, and many insulation fibrous materials. All molds require some form of moisture to grow however, like temperature, the amount of moisture varies for different species. Some are xerophillic (colonize under very dry conditions) some are xerotolerant (colonize under a wide range of moisture levels) and some are hydrophilic (colonize at high moisture levels). It does not have to be a leak. . . Humidity or moisture content of the substrate can often be sufficient (relative humidity 50% start becoming problematic in many indoor cases.) It can spread very easily through any HVAC system.

Mycotoxins are examples of chemical substances that molds create generally as secondary metabolites, thought to possibly play a role in either helping to prepare the substrate on which they exist for digestion, as defense mechanisms, and some have suggested that they may be produced when the organisms are under stress, which could be related to competition/defense, or simply due to inhospitable environmental conditions. The mycotoxins, which are also neurotoxins (a toxin that is determined to cause neurological damage), most commonly reach people from the air, via spores from the molds in question. They are also found in small particulates at times which may often represent mold dust, small particles of mold that has dried and turned to dust. Spores, when inhaled, can begin to colonize in the sinuses and throughout the body, including the brain, lung and gut after a period of time.

One of the mycotoxins, aflatoxin, is produced by the fungi Penicillium, Aspergillus flavus and Aspergillus parasiticus. Four different aflatoxins, B1, B2, G1 and G2, have been identified with B1 being the most toxic, carcinogenic and prevalent. Another very dangerous family of toxin producers is Fusarium. The toxins zearalenone, trichothecenes or moniliformin can be formed by various types of Fusarium including F. moniliforme, F. oxysporum, F. culmorum, F. avenaceum, F. equiseti, F. roseum, and F. nivale.

Under certain growth and environmental conditions, black mold, otherwise known as Stachybotrys chartarum may produce several different mycotoxins, including a very strong class known as trichothecenes. Trichothecenes are also produced by several common molds including species in the genera Acremonium, Cylindrocarpon, Dendrodochium, Myrothecium, Trichoderma, and Trichothecium. The trichothecenes are potent inhibitors of DNA, RNA, and protein synthesis, and have been well studied in animal models because of concern about their potential misuse as agents of biological warfare, due to their ability to destroy human health (mentally and physically), and never show up in an autopsy. Sick buildings are one of the three major causes of fungal illness in industrialized nations today.