Dispersion of Exhalation Pollutants in a Two-bed Hospital Ward with a Downward Ventilation System

Hua Qian, Peter V. Nielsen, Carl-Erik Hyldgård

Research output: Contribution to journalJournal articleResearchpeer-review

78 Citations (Scopus)

Abstract

The Centers for Disease Control and Prevention has recommended the use of downward ventilation systems in isolation rooms to reduce the risk of cross-infection from airborne transmissible diseases. The expected airflow pattern of a downward ventilation design would supply cooler and slightly heavier clean air from a ceiling diffuser to push down contaminants, which would then be removed via outlets at floor level. A "laminar" (strictly speaking, unidirectional) flow is expected to be produced to avoid flow mixing and thus reduce cross-infection risk. Experiments were carried out in a full-scale experimental hospital ward with a downward ventilation system to investigate the possibility of applying downward ventilation in a general hospital ward. Two life-sized breathing thermal manikins were used to simulate a source patient and a receiving patient. Computation fluid dynamics was also used to investigate the airflow pattern and pollutant dispersion in the test ward. Based on both experimental and numerical results, the laminar airflow pattern was shown to be impossible to achieve due to turbulent flow mixing and flow entrainment into the supply air stream. The thermal plumes produced above people were found to induce flow mixing. We also studied the effects of the locations of the supply and extraction openings on both the flow pattern and pollutant exposure level in the occupied zone. A number of practical recommendations are suggested.
Original languageEnglish
JournalBuilding and Environment
Volume43
Issue number3
Pages (from-to)344-354
Number of pages11
ISSN0360-1323
DOIs
Publication statusPublished - 13 Dec 2006

Fingerprint

Hospital beds
pollutant
Ventilation
ventilation
air
supply
airflow
Disease
social isolation
Thermal plumes
Disease control
Air entrainment
disease control
experiment
Ceilings
fluid dynamics
Air
Fluid dynamics
turbulent flow
flow pattern

Keywords

  • Infection control
  • Downward ventilation
  • Hospital ventilation
  • Airborne transmission
  • Breathing exhalation jet
  • Flow visualization

Cite this

@article{e165da50a13911de8c1c000ea68e967b,
title = "Dispersion of Exhalation Pollutants in a Two-bed Hospital Ward with a Downward Ventilation System",
abstract = "The Centers for Disease Control and Prevention has recommended the use of downward ventilation systems in isolation rooms to reduce the risk of cross-infection from airborne transmissible diseases. The expected airflow pattern of a downward ventilation design would supply cooler and slightly heavier clean air from a ceiling diffuser to push down contaminants, which would then be removed via outlets at floor level. A {"}laminar{"} (strictly speaking, unidirectional) flow is expected to be produced to avoid flow mixing and thus reduce cross-infection risk. Experiments were carried out in a full-scale experimental hospital ward with a downward ventilation system to investigate the possibility of applying downward ventilation in a general hospital ward. Two life-sized breathing thermal manikins were used to simulate a source patient and a receiving patient. Computation fluid dynamics was also used to investigate the airflow pattern and pollutant dispersion in the test ward. Based on both experimental and numerical results, the laminar airflow pattern was shown to be impossible to achieve due to turbulent flow mixing and flow entrainment into the supply air stream. The thermal plumes produced above people were found to induce flow mixing. We also studied the effects of the locations of the supply and extraction openings on both the flow pattern and pollutant exposure level in the occupied zone. A number of practical recommendations are suggested.",
keywords = "Infection control, Downward ventilation, Hospital ventilation, Airborne transmission, Breathing exhalation jet, Flow visualization",
author = "Hua Qian and Nielsen, {Peter V.} and Carl-Erik Hyldg{\aa}rd",
year = "2006",
month = "12",
day = "13",
doi = "doi:10.1016/j.buildenv.2006.03.025",
language = "English",
volume = "43",
pages = "344--354",
journal = "Building and Environment",
issn = "0360-1323",
publisher = "Pergamon Press",
number = "3",

}

Dispersion of Exhalation Pollutants in a Two-bed Hospital Ward with a Downward Ventilation System. / Qian, Hua; Nielsen, Peter V.; Hyldgård, Carl-Erik.

In: Building and Environment, Vol. 43, No. 3, 13.12.2006, p. 344-354.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Dispersion of Exhalation Pollutants in a Two-bed Hospital Ward with a Downward Ventilation System

AU - Qian, Hua

AU - Nielsen, Peter V.

AU - Hyldgård, Carl-Erik

PY - 2006/12/13

Y1 - 2006/12/13

N2 - The Centers for Disease Control and Prevention has recommended the use of downward ventilation systems in isolation rooms to reduce the risk of cross-infection from airborne transmissible diseases. The expected airflow pattern of a downward ventilation design would supply cooler and slightly heavier clean air from a ceiling diffuser to push down contaminants, which would then be removed via outlets at floor level. A "laminar" (strictly speaking, unidirectional) flow is expected to be produced to avoid flow mixing and thus reduce cross-infection risk. Experiments were carried out in a full-scale experimental hospital ward with a downward ventilation system to investigate the possibility of applying downward ventilation in a general hospital ward. Two life-sized breathing thermal manikins were used to simulate a source patient and a receiving patient. Computation fluid dynamics was also used to investigate the airflow pattern and pollutant dispersion in the test ward. Based on both experimental and numerical results, the laminar airflow pattern was shown to be impossible to achieve due to turbulent flow mixing and flow entrainment into the supply air stream. The thermal plumes produced above people were found to induce flow mixing. We also studied the effects of the locations of the supply and extraction openings on both the flow pattern and pollutant exposure level in the occupied zone. A number of practical recommendations are suggested.

AB - The Centers for Disease Control and Prevention has recommended the use of downward ventilation systems in isolation rooms to reduce the risk of cross-infection from airborne transmissible diseases. The expected airflow pattern of a downward ventilation design would supply cooler and slightly heavier clean air from a ceiling diffuser to push down contaminants, which would then be removed via outlets at floor level. A "laminar" (strictly speaking, unidirectional) flow is expected to be produced to avoid flow mixing and thus reduce cross-infection risk. Experiments were carried out in a full-scale experimental hospital ward with a downward ventilation system to investigate the possibility of applying downward ventilation in a general hospital ward. Two life-sized breathing thermal manikins were used to simulate a source patient and a receiving patient. Computation fluid dynamics was also used to investigate the airflow pattern and pollutant dispersion in the test ward. Based on both experimental and numerical results, the laminar airflow pattern was shown to be impossible to achieve due to turbulent flow mixing and flow entrainment into the supply air stream. The thermal plumes produced above people were found to induce flow mixing. We also studied the effects of the locations of the supply and extraction openings on both the flow pattern and pollutant exposure level in the occupied zone. A number of practical recommendations are suggested.

KW - Infection control

KW - Downward ventilation

KW - Hospital ventilation

KW - Airborne transmission

KW - Breathing exhalation jet

KW - Flow visualization

U2 - doi:10.1016/j.buildenv.2006.03.025

DO - doi:10.1016/j.buildenv.2006.03.025

M3 - Journal article

VL - 43

SP - 344

EP - 354

JO - Building and Environment

JF - Building and Environment

SN - 0360-1323

IS - 3

ER -