Adequacy of air change rate as the sole indicator of an air distribution system's effectiveness to mitigate airborne infectious disease transmission caused by a cough release in the room with overhead mixing ventilation: A case study

In indoor environments where airborne infectious disease transmission is of concern, air change rate is conventionally used as the sole indicator of air delivery system performance. This indicator, based on the total volume dilution reasoning, suggests that increase of the supply flow rate will reduce risk of airborne infectious disease transmission. Results obtained from recent studies on cough release conducted in the field environmental chamber (FEC) at the National University of Singapore indicate that increase of supply flow rate may cause increase in the airborne infection risk transmission for several positions of the cough source and the susceptible person in relation to the supply and return air grills. Particle image velocimetry (PIV) was used for airflow field investigation, while a Grimm 1.108 aerosol counter was used to measure droplet concentration in the FEC. Results from this study imply that a local airflow pattern is an important factor influencing dispersion of cough droplets and consequential exposure. It is demonstrated that increase in supply flow rate can lead to an increase in exposure under certain circumstances. This further implies that air change rate should not be used as the sole indicator of the air delivery system's ability to reduce exposure to airborne infectious droplets.

[1]  C. Liao,et al.  Modeling control measure effects to reduce indoor transmission of pandemic H1N1 2009 virus , 2013 .

[2]  A. Melikov,et al.  Exposure to exhaled air from a sick occupant in a two-bed hospital room with mixing ventilation: effect of distance from sick occupant and air change rate , 2011 .

[3]  Povl Ole Fanger,et al.  Airflow characteristics in the occupied zone of ventilated spaces , 1987 .

[4]  William P. Bahnfleth,et al.  Filtration of airborne microorganisms: Modeling and prediction , 1999 .

[5]  Bin Zhao,et al.  Modeling particle dispersion in personalized ventilated room , 2007 .

[6]  C. Liao,et al.  Modelling control measures to reduce the impact of pandemic influenza among schoolchildren , 2007, Epidemiology and Infection.

[7]  Peter V. Nielsen,et al.  Risk of cross-infection in a hospital ward with downward ventilation , 2010 .

[8]  L. Sehulster,et al.  Guidelines for environmental infection control in health-care facilities. Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC). , 2003, MMWR. Recommendations and reports : Morbidity and mortality weekly report. Recommendations and reports.

[9]  Bin Zhao,et al.  Some questions on dispersion of human exhaled droplets in ventilation room: answers from numerical investigation. , 2010, Indoor air.

[10]  S. Kato,et al.  Study on transport characteristics of saliva droplets produced by coughing in a calm indoor environment , 2006 .

[11]  Jovan Pantelic,et al.  Personalized ventilation as a control measure for airborne transmissible disease spread , 2009, Journal of The Royal Society Interface.

[12]  M. P. Wan,et al.  Transport and Removal of Expiratory Droplets in Hospital Ward Environment , 2008 .

[13]  H. Holmgren,et al.  Relation between humidity and size of exhaled particles. , 2011, Journal of aerosol medicine and pulmonary drug delivery.

[14]  M. P. Wan,et al.  Experimental Study of Dispersion and Deposition of Expiratory Aerosols in Aircraft Cabins and Impact on Infectious Disease Transmission , 2009 .

[15]  Cover Sheet.  DROPLET FATE IN INDOOR ENVIRONMENTS , OR CAN WE PREVENT THE SPREAD OF INFECTION ? , 2007 .

[16]  Vipin Kaushal.  Environmental Control Including Ventilation In Hospitals , 2004 .

[17]  Jovan Pantelic,et al.  A preference driven multi-criteria optimization tool for HVAC design and operation , 2012, Energy and Buildings.

[18]  Shelly L. Miller,et al.  Particle Image Velocimetry of Human Cough , 2011 .

[19]  Wei Sun,et al.  Dispersion and settling characteristics of evaporating droplets in ventilated room , 2007 .

[20]  Yigang Sun,et al.  Experimental characterization of airflows in aircraft cabins, Part II: Results and research recommendations. Discussion , 2005 .

[21]  H. Qian,et al.  Removal of exhaled particles by ventilation and deposition in a multibed airborne infection isolation room. , 2010, Indoor air.

[22]  J. Decker.  Case Studies: Evaluation of Isolation Rooms in Health Care Settings Using Tracer Gas Analysis , 1995 .

[23]  Arsen Krikor Melikov,et al.  Methods for air cleaning and protection of building occupants from airborne pathogens , 2008, Building and Environment.

[24]  C. Fraser,et al.  Factors that make an infectious disease outbreak controllable. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[25]  Arsen Krikor Melikov,et al.  Exposure of health care workers and occupants to coughed airborne pathogens in a double-bed hospital patient room with overhead mixing ventilation , 2012, HVAC&R Research.

[26]  K. Kerr,et al.  Virus diffusion in isolation rooms , 2006, Journal of Hospital Infection.

[27]  Tu Guangbei,et al.  Study on biological contaminant control strategies under different ventilation models in hospital operating room , 2008 .

[28]  M. Rupp.  HOSPITAL EPIDEMIOLOGY AND INFECTION CONTROL, 2ND EDITION , 2000 .

[29]  C. Chao,et al.  A study of the dispersion of expiratory aerosols in unidirectional downward and ceiling-return type airflows using a multiphase approach. , 2006, Indoor air.

[30]  A. Melikov,et al.  Protection of Occupants from Exhaled Infectious Agents and Floor Material Emissions in Rooms with Personalized and Underfloor Ventilation , 2007 .

[31]  P V Nielsen,et al.  Dispersion of exhaled droplet nuclei in a two-bed hospital ward with three different ventilation systems. , 2006, Indoor air.

[32]  K. Mengersen,et al.  Characterization of expiration air jets and droplet size distributions immediately at the mouth opening , 2008, Journal of Aerosol Science.

[33]  K. Tham,et al.  Assessment of the mixing air delivery system ability to protect occupants from the airborne infectious disease transmission using Wells–Riley approach , 2012, HVAC&R Research.

[34]  Yigang Sun,et al.  Experimental characterization of airflows in aircraft cabins, Part I: Experimental system and measurement procedure. Discussion , 2005 .

[35]  M. First,et al.  Guidelines for the application of upper-room ultraviolet germicidal irradiation for preventing transmission of airborne contagion -- Part 1: Basic principles , 1999 .

[36]  A. Melikov,et al.  Exposure of health care workers and occupants to coughed air in a hospital room with displacement air distribution: impact of ventilation rate and distance from coughing patient , 2012 .

[37]  S. McGuire.  State Indicator Report on Fruits and Vegetables, 2013, Centers for Disease Control and Prevention, Atlanta, GA. , 2013, Advances in nutrition.

[38]  A. Melikov.  Personalized ventilation. , 2004, Indoor air.

[39]  Shuzo Murakami,et al.  Study on inhalation region by means of CFD analysis and experiment , 2005 .

[40]  Hannu Koskela,et al.  Different Types of Door-Opening Motions as Contributing Factors to Containment Failures in Hospital Isolation Rooms , 2013, PloS one.

[41]  Bin Zhao,et al.  Particle dispersion and deposition in ventilated rooms: Testing and evaluation of different Eulerian and Lagrangian models , 2008 .

[42]  C. Buppert.  Occupational Health: Recognizing and Preventing Work-related Disease and Injury, 4th Edition , 2001 .

[43]  J. Duguid,et al.  The size and the duration of air-carriage of respiratory droplets and droplet-nuclei , 1946, Epidemiology and Infection.

[44]  Yang-Cheng Shih,et al.  Numerical study on the dispersion of airborne contaminants from an isolation room in the case of door opening , 2008, Applied Thermal Engineering.

[45]  Benjamin J. Cowling,et al.  Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks , 2010, Occupational and Environmental Medicine.

[46]  P V Nielsen,et al.  Role of ventilation in airborne transmission of infectious agents in the built environment - a multidisciplinary systematic review. , 2007, Indoor air.

[47]  A. Hubbard,et al.  Toward Understanding the Risk of Secondary Airborne Infection: Emission of Respirable Pathogens , 2005, Journal of occupational and environmental hygiene.

[48]  M. Sandberg,et al.  Building Ventilation: Theory and Measurement , 1996 .

[49]  E. A. Hathway,et al.  The ventilation of multiple-bed hospital wards: review and analysis. , 2008, American journal of infection control.

[50]  C. Chao,et al.  Transport characteristics of expiratory droplets and droplet nuclei in indoor environments with different ventilation airflow patterns. , 2007, Journal of biomechanical engineering.

[51]  M. S. Zuraimi,et al.  Removing indoor particles using portable air cleaners: Implications for residential infection transmission , 2011 .

[52]  I. Eames,et al.  Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises , 2006, Journal of Hospital Infection.

[53]  I. Eames,et al.  Airborne transmission of disease in hospitals , 2009, Journal of The Royal Society Interface.

[54]  Yigang Sun,et al.  An Overview of Room Air Motion Measurement: Technology and Application , 2007 .