The objective of our study is to investigate the reasons why 21 persons suffered erythema and other skin changes, and conjunctivae infection after staying in a closed room for three hours. A multi-disciplinary case study including interviews, building and ventilation inspections, was performed by a multidisciplinary team comprising a medical epidemiologist, and an industrial hygienist. A self-administered questionnaire was designed to determine the magnitude of the health problem of the affected students. By a process of investigative elimination, we deduced that the symptoms were caused by accidental exposure to ultraviolet C radiation where it was radiated from the germicidal ultraviolet lamps. The most common symptoms and signed presented were erythema of skin and conjunctivae infection. The erythema of skin and conjunctivae infection arose from exposure to ultraviolet C radiation and that safeguards are needed to ensure ultraviolet germicidal lamps are not accidentally switched on while a room is occupied.