CFD Analysis of the Performance of a Local Exhaust Ventilation System in a Hospital Ward

Abstract

Healthcare workers (HCWs) are at high risk of nosocomial infection as they frequently perform medical procedures on infectious patients that may generate bioaerosols. For example, emergency endotracheal intubations for severe acute respiratory syndrome (SARS) patients. Due to the high zonal bioaerosol concentration close to infection sources (e.g. patient’s breathing zone) local exhaust ventilation (LEV) has been identified as a practical solution to reduce the bioaerosol concentration in hospital wards. In this study, computational fluid dynamic (CFD) models have been developed to simulate the transport of infectious droplets and bioaerosols in a hospital ward to aid the design and control of a LEV system. This paper reports the details of the CFD mathematical models as well as the analyses of the distribution and suspension time of droplets and bioaerosols with respect to their size, emission direction, and emission speed. It is shown that the operation of a well-designed LEV system can effectively remove infectious droplets and bioaerosols from the breathing zone of a HCW.

Keywords

Computational fluid dynamic (CFD)Mathematical model Local exhaust ventilation (LEV)Bioaerosols Nosocomial infection

Get full access to this article

View all access options for this article.

References

Hospital Authority: HKSAR, http://www.ha.org.hk/sars/sars_index_e.html. Severe Acute Respiratory Syndrome homepage 2005 (accessed March 2006).

Seto WH , Tsang D , Yung RWH , Ching TY , Ng TK , Ho M , Ho LM , Peiris JSM , Advisors of Expert SARS group of Hospital Authority : Effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (SARS) : Lancet 2003;361: 1519-1520 .

World Health Organization (WHO) : Consensus Document on the Epidemiology of Severe Acute Respiratory Syndrome (SARS), 2003. http://www.who.int.csr/sars/en/WHOconsensus.pdf.

Gamage B , Moore D , Copes R , Yassi A , Bryce E : Protecting health care workers from SARS and other respiratory pathogens: a review of the infection control literature : AJIC State of the Science Report 2003;33: 114-121 .

Li Y , Huang X , Yu ITS , Wong TW , Qian H : Role of air distribution in SARS transmission during the largest nosocomial outbreak in Hong Kong : Indoor Air 2004;15: 83-95 .

ASHRAE . Chapter 29 - Industrial Local Exhaust Systems. ASHRAE Handbook: HVAC Applications, SI Edition, Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. , 1999.

ACGIH . Industrial Ventilation: A Manual of Recommended Practice, 24th edition , American Conference of Governmental Industrial Hygienists, Cincinnati, OH, 2001.

Leung MKH , Chau OKY , Liu C-H : Local exhaust ventilation for infection control in hospitals : Hong Kong Institute of Engineers - Trans 2005;12: 27-32 .

FLUENT. http://www.fluent.com/. FLUENT homepage 2004.

10.

Wells, WF : Airborne Contagion and Air Hygiene, an Ecological Study of Droplet Infections, Harvard University Press, Cambridge, MA , 1955.

11.

Deacon J : The Microbial World: Airborne Micro-organisms, http://helios.bto.ed.ac.uk/bto/microbes/airborne.htm. Institute of Cell and Molecular Biology, The University of Edinburgh , 2004.