Airborne Gram-negative bacteria contamination has been demonstrated in several environments like cotton or flax factories, rooms with humidifiers and sewage treatment plants. Inhalation of LPS by animals provokes a bronchial invasion by neutrophils, a platelet aggregation in pulmonary capillaries, a local immune response and fever. Inhalation by human is related with clinical symptoms like fever, chills, malaise, muscle and joint aches and chest thightness. It appears from data in the literature that LPS airborne contamination is sufficient to provoke such symptoms. It seems important to study more precisely the contamination of suspected air in presence of these symptoms.