Effect of Air Stability on the Dispersal of Exhaled Contaminant in Rooms

Chunwen Xu, Guangcai Gong, Peter V. Nielsen, Li Liu, Rasmus Lund Jensen

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review


Experiments are conducted in a full-scale chamber equipped with whole floor and whole ceiling supply or exhaust to form approximately zero and larger temperature gradients corresponding to unstable and stable air conditions. It can be observed that the air with smoke exhaled from a life-sized thermal manikin is locked and stratified at certain heights at stable condition while it mixes well with the ambient air and is diluted quickly through upper openings when the air is relatively unstable. The concentration of contaminant simulated by tracer gas (N2O) is measured both around and 0.35m from the manikin, indicating that the person who exhales the contaminant may not be polluted by himself as the protective effect of the thermal boundary layer around the body, especially in stable condition with two concentration zones and clean air drawn from the inlets. However, other persons facing the respiration some distance away may suffer higher contaminant exposure if the air in room is quite stable and contaminant from the mouth can penetrate a longer horizontal distance. In addition, the air stability slightly changes the velocity profiles, giving higher velocity decay and more turbulent mixing with surrounding air at unstable air condition.
Original languageEnglish
Title of host publicationProceedings of SET 2013 : 12th International Conference on Sustainable Energy Technologies
Number of pages5
PublisherThe Hong Kong Polytechnic University
Publication date2013
Article numberSET2013-401
Publication statusPublished - 2013
EventThe International Conference on Sustainable Energy Technologies - Hong Kong, China
Duration: 26 Aug 201329 Aug 2013
Conference number: 12


ConferenceThe International Conference on Sustainable Energy Technologies
CityHong Kong
Internet address

Bibliographical note

Paper no. 401


  • Air stability
  • Contaminant
  • Exhalation
  • Full-scale experiments

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