In February 2017, Santé publique France (Occitanie region) was contacted regarding a report of an odor problem at a research center. Since April 2016, episodes of odors (described as smelling like solvents or ether) have been causing significant discomfort to staff working in the animal facility building. Most of these staff members described symptoms such as headaches, nausea, vomiting, and respiratory tract irritation. A meeting held in April 2017 provided an opportunity to present and propose to all stakeholders the investigative approach recommended by Santé publique France, in accordance with the guidelines for the diagnosis and management of unexplained mass illness. The investigations were conducted by a multidisciplinary team and consisted of four components: epidemiological, clinical, environmental, and psychosocial. Six out of eight people working in the pet store at the time of the epidemiological investigation experienced symptoms. In 2017, five out of eight employees were affected, on average once a week. The symptoms are mild, relatively brief, reversible, and mostly do not worsen over time, but can be debilitating for daily work. The simultaneous occurrence of odors and symptoms does not support the notion of an exclusively psychosocial phenomenon. The most plausible hypothesis involves contamination of the wastewater system. Tests conducted in late 2017 in the wastewater system revealed the presence of chloroform, albeit at relatively low levels, an odor consistent with the ethereal scent described by employees. Chloroform or other chlorinated byproducts can indeed form through the action of chlorine on organic matter, as biology laboratories discharge large quantities of bleach down the sink upstream from the animal facility. Several proposals to guide effluent management measures were put forward following these investigations.