Building biology (or Baubiologie) is a field of building science investigating the indoor living environment for a variety of irritants. Practitioners study how the environment of residential, commercial and public buildings can affect the health of the occupants, producing a restful or stressful environment. Important areas of building biology are building materials and processes, electromagnetic fields (EMFs) and radiation (EMR) and indoor air quality (IAQ).There are 25 principles of building biology, which govern the decision making of building biologists.