The key case of the project is the investigation of cross infection between two persons. Furthermore two human body’s properties such as a thermal plume and an exhalation are examined. All experiments are conducted in a full scale room with dimensions 410 x 320 x 270. Two manikins with human body’s functions including breathing and heat load releasing are used. Semi – circular diffuser is placed on the floor to provide displacement ventilation. Tracer gas is utilized for simulating gaseous contaminants. Three indoor air parameters (air velocity, temperature and concentration of contaminants) are measured and distributions of them are presented. In addition CFD simulations are performed. Results show that a level of cross infection depends significantly on positions and distance between two people. Furthermore thermal plume is kind of protection against cross infection. Finally displacement ventilation is found not to be the perfect way of removing contaminants from breathing zone.