When there is an unpleasant mystery odor in a home, school, office or other type of building, it could cause everything from a nuisance to something that signals potential short- or long-term health concerns for building occupants. These types of odors could even lower property values. In commercial and institutional settings, odors may result in decreased productivity, increased absenteeism and higher employee turnover rates., , , , Mystery odors could be coming from mold, bacteria, sewer ga.