Modern, non-industrial workplaces may, because of building techniques, widespread use of synthetic materials and artificial ventilation, create risks for the health and well-being of workers. Indoor air pollution by chemical, biological and sometimes physical agents constitutes a significant risk factor, particularly for the respiratory system. The most common effects of exposure to, and inhalation of, indoor air pollutants include acute and chronic inflammations, acute worsening of pre-existing respiratory symptoms or illnesses and airway sensitization to indoor allergens. Upper airway disturbances with an allergic or irritative aetiology are very frequent; Asthma and Hypersensitivity Pneumonitis are more rarely reported but may become severe and widespread when certain environmental conditions prevail. Respiratory infections may have a human source such as tuberculosis or viral diseases or may originate in ventilation systems such as Legionnaire's disease (Legionella pneumophila pneumonia). As all these pathologies may have high social and economic costs and appropriate therapy is not always available, the specialist in Occupational Medicine plays a pre-eminent role in early diagnosis and prevention of respiratory diseases linked to indoor air pollution in the workplace.