When mold moves indoors, however, it has few predators and optimal temperature conditions exist for growth. All it takes is some moisture from a leaking pipe or high humidity, moderate temperatures and a food source such as wood or paper to provide mold with everything it needs to quickly establish large colonies. From there, fungal spores are distributed throughout the building via the HVAC systems, where they land on food and are ingested or breathed in by the occupants. If the mold happens to be producing toxins, serious health consequences can occur, including liver & kidney tumors and neurological damage.

Some of the signs of indoor fungal growth include a musty odor in the building, visible growth on buidling materials or personal belongings, and allergic reactions and sometimes severe respiratory and neurological complications by the occupants. Symptoms may occur long before the odor or visible signs appear, which is why ESG investigators always attempt to collect some health history data during a mold investigation.

There are a relatively small number of molds that thrive indoors, which is good news as a very small percentage of the world's fungi have been studied for their association with human health. According to the CDC, about 500 of the 100,000 known fungal species are thought to be harmful to people. Unfortunately, many of the molds found indoors have been classified as allergenic, pathogenic or toxigenic. Simply put, this means that many indoor molds affect health to some degree.

Will everyone working or living in a building have the same reaction to mold? Not at all, which can present a challenge to the occupants and the mold investigator. Some people can be exposed to massive amounts of airborne mold spores and have no apparent reaction. Others are exposed to a few spores and their immune systems react quickly and severely. Either way, research has proven that long-term exposure to a small amount of fungal spores is unhealthty at best and can prove deadly.