In a laboratory office setting with four occupants facing the walls, local emission of a tracer gas (B) in the breathing zone of one infected occupant mimics the transmission of an air-borne disease. At the same time, another tracer gas (A) is homogeneously emitted in the office space so that the local mean age can be determined in each sampling point. Tracers are passively collected in the breathing zones of the occupants and in sixteen sampling positions distributed at four heights. A laboratory office setup with mixing ventilation conditions and a single ceiling exhaust in a corner is investigated. The distribution of B-tracer is analyzed in the sampling points for the four possible locations of an infected occupant in relation to the exhaust location. The results reported are in the absence of thermal plumes, i.e., the manikins representing occupants were turned off. The relative apparent emission rates calculated from the measurements are conjectured to represent the steady state transfer probabilities from the respective breathing zones. As expected, for mixing ventilation conditions, the steady state probabilities to most positions are similar. Nevertheless, the steady state transfer probabilities from the breathing zones of the pair of manikins closer to the exhaust cause slightly more spreading, 0.83 ± 0.04 and 0.82 ± 0.04, than the other pair, 0.76 ± 0.03 and 0.75 ± 0.06.