Numerical investigation of required mechanical exhaust rate to avoid expiration from open windows caused by Buoyancy

Yan Wu, Jianlei Niu, Naiping Gao

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review


Airborne transmission is the primary way for the spread of infectious diseases. A specific transmission route that contaminants expire from the lower-floor window and then re-enter the upper-floor window has been verified widely. This study aims at the possible control of this spread route, and the effects of mechanical exhaust are investigated. The required minimum mechanical exhaust rate to eliminate the expiration from windows due to buoyancy is calculated. Further, the relationships between the required exhaust rate and two factors, indoor/outdoor temperature difference and window height, are analysed. It is found that such a minimum mechanical exhaust rate exists and it varies with both the temperature difference and window height. Specifically, it is 10 ACH when the temperature difference is 5°C and window height is 0.4m, and when the temperature difference and window height are doubled, the required minimum exhaust rate rises by 40% and 20% respectively. This study offers a preliminary insight into more effective control of infectious diseases.
Original languageEnglish
Title of host publicationIndoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate
PublisherInternational Society of Indoor Air Quality and Climate
Number of pages8
Publication statusPublished - 1 Jan 2014
Event13th International Conference on Indoor Air Quality and Climate, Indoor Air 2014 - Hong Kong, Hong Kong
Duration: 7 Jul 201412 Jul 2014


Conference13th International Conference on Indoor Air Quality and Climate, Indoor Air 2014
Country/TerritoryHong Kong
CityHong Kong


  • Buoyancy effects
  • CFD simulation
  • Control of infectious diseases
  • Expiration from open windows
  • Mechanical exhaust

ASJC Scopus subject areas

  • Pollution
  • Building and Construction
  • Health, Toxicology and Mutagenesis
  • Computer Science Applications

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