1 Indoor Environmental Engineering, The Faculty of Engineering and Science, Aalborg University, VBN2 Division of Architectural Engineering, The Faculty of Engineering and Science, Aalborg University, VBN3 Department of Civil Engineering, The Faculty of Engineering and Science, Aalborg University, VBN4 The Faculty of Engineering and Science, Aalborg University, VBN5 Department of Mechanical Engineering, The University of Hong Kong
Airborne cross infection is based on transmission of microorganisms attached to exhaled droplets or particles. Traditionally two transmission routes are considered, namely via droplet nuclei (< 5-10 μm) and via droplets (> 5-10 μm), and they correspond to two infection routes: droplet infection and airborne infection. A transition may take place from droplet-borne infection to airborne infection, because the exhaled droplets may evaporate in the air and droplets become droplet nuclei. Full-scale experiments on the movement of droplet nuclei (airborne infection) have been performed in a number of experiments using breathing thermal manikins and tracer gas for the simulation of microorganism-laden particles movement in indoor and outdoor environment. Full-scale experiments are conducted with droplet movement (droplet infection) using one or two thermal manikins. First the paper will discuss earlier measurements on the flow in the microenvironment around persons with respect to droplet nuclei (< 5- 10 μm). Measurement of settled particles (droplets > 5-10 μm) on the floor around a manikin (person) will then be shown for different heat releases from the manikin. These results are in good agreement with the expectation of a settlement within a “short” distance of 1.5 m, Lidwell and Williams (1961). Experiments with the exhalation of particles from a source manikin close to the other manikin are also performed. The results show that in this case the change in the microenvironment will influence the particle distribution in the proximity surrounding of the manikins.