Mold is a fungi that is found both indoors and outdoors. Mold spores are invisible to the naked eye and float through the air. Mold can grow on any organic surface, such as wood, paper, carpet, and food. When mold grows, it releases spores into the air which can cause respiratory problems for people with allergies or asthma. Mold can also cause structural damage to buildings. Mold testing is the process of identifying and measuring the level of mold in an environment.