Molds are microbiological organisms that break down dead organic matter on the earth. If that dead organic matter is used as part of the construction of a house or building, molds will grow if sufficient water is present. In addition to gradually undermining the structural integrity of building materials, mold growth can also lead to health problems for building occupants. Exposure to molds and byproducts they produce has been linked to severe allergic reactions, asthma and upper respiratory infections. Because of this risk the Texas Department State Health Services requires that professionals who assess for and carry out mold remediation projects in Texas be trained and certified.