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Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Presented by Faatiema Salie f CSIR Built Environment Monday.

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Presentation on theme: "Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Presented by Faatiema Salie f CSIR Built Environment Monday."— Presentation transcript:

1 Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Presented by Faatiema Salie f CSIR Built Environment Monday 25 July 2011

2 Overview of the presentation: Airborne transmission of TB TB IPC – focus on environmental control measures What is ventilation? And how can it be used in TB IPC? Important concepts in ventilation design “Open this window – Fresh air fights TB” Case studies Measurements and instrumentation Things to take with you from this presentation Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation

3 The airborne transmission of TB Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Illustration of particle dispersal when a person sneezes Large droplets fall to the floor Smaller drops become aerosolised Droplet nuclei of about 5 microns are formed Environmental conditions must be conducive to pathogen survival (Temperature, humidity)

4 TB Infection Prevention and Control Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Personal Environmental Administrative What measures can be taken to minimise the opportunity for infectious particles to be liberated into the air? What measures can be taken to remove infectious particles from the air? What measures can be taken to protect ourselves against infection?

5 Ventilation as a solution for TB IPC Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation C is the expected number of new cases S is the number of exposed susceptible individuals I is the number of sources of infectious aerosols q is the generation rate of infectious agents p is the breathing rate of exposed individuals t is the exposure time Q is the ventilation rate

6 Concepts of ventilation – The dilution principle Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation

7 Concepts of ventilation – The dilution principle Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation The first air change removes 63% of potentially infectious droplets inlet exhaust

8 Concepts of ventilation – The dilution principle Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation The second air change removes 84% of potentially infectious droplets inlet exhaust

9 Concepts of ventilation – The dilution principle Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation The WHO and CDC recommends 12 ACH for TB IPC in high risk settings Why 12 ACH? It will take approximately 24 minutes to remove 99.9% of infectious droplets at 12 ACH

10 Concepts of ventilation – The airflow pattern Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Airflow should be from clean areas to “dirty” areas Contaminated air should be exhausted directly to the outside.

11 Can we successfully achieve these ventilation standards? Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Mechanical ventilation - ventilation rate, pressure cascading, thermal comfort, etc. Airborne Infection Isolation Rooms (AIIRs) Filtration, exhaust design Maintenance Cost of an effective system?

12 Can we successfully achieve these ventilation standards in our resource constrained settings? Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Natural ventilation

13 Can we successfully achieve these ventilation standards in our resource constrained settings? Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Wind pressure and buoyancy forces Single-sided and cross-ventilation Stack effect

14 Can we successfully achieve these ventilation standards in our resource constrained settings? Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Natural ventilation – ventilation rates? pressure cascading? thermal comfort? Maintenance? Costs?

15 Lets apply these principles by looking at some case studies Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation

16 Investigating solutions for home-based care (CSIR 2011) Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation

17 Investigating solutions for home-based care, CSIR 2011 Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Typical subsidy house Where is patient most likely to be? Ventilation rates? Airflow patterns?

18 Investigating solutions for home-based care, CSIR 2011 Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation

19 Investigating solutions for home-based care, CSIR 2011 Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation All windows closed Bedroom 2 window open

20 Investigating solutions for home-based care, CSIR 2011 Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Cross-ventilation Single-sided ventilation with cross- ventilation

21 Investigating solutions for home-based care, CSIR 2011 Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation All windows closed – 0.6 ACH Bedroom 2 window opened – 8 ACH Cross-ventilation – 17 ACH Single-sided ventilation with cross-ventilation – 7 ACH

22 Measurements and Instruments Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation Predominant wind conditions Windward and leeward side Measure on the windward side velocity Measure the openable area Calculate the flow rate, Q = A x v We can relate the flow rate to ACH via the volume of the room Time-dependant calculations

23 W Kowalski. Ultraviolet germicidal irradiation handbook. – UVGI for air and surface disinfection. Springer Department of Health and Human Services., Centers for Disease Control and Prevention., National Institute for Occupational Safety and Health., Environmental Control for Tuberculosis: Basic Upper-Room Ultraviolet Germicidal Irradiation Guidelines for Healthcare Settings. Escombe, R.A., Moore, D.J.A., Gilman, R.H., Navincopa, M., Ticona, E., Mitchell, B., Noakes, C,. Martı´nez, C., Sheen,P., Ramirez, R., Quino, W., Gonzalez, A., Friedland, J.S., Evans, C.A., Natural Ventilation for the Prevention of Airborne Contagion. PLoS Medicine 6:3, Escombe, R.A., Oese, C.C., Gilman, R.H., Navincopa, M., Pan, W., Martı´nez, C., Chacaltana, J., Rodrı´guez, R., Moore, D.J.A., Friedland, J.S., Evans, C.A., Upper-Room Ultraviolet Light and Negative Air Ionization to Prevent Tuberculosis Transmission PLoS Medicine 4:2, Nardell, E.A., Progress in the Application of Ultraviolet Germicidal Irradiation. American Society for Photobiology. Powerpoint accessed Xu, P., Peccia, J., Fabian, P., Martyny, J.W., Fennelly, K.P., Hernandez, M., Miller S.L., Efficacy of ultraviolet germicidal irradiation of upper-room air in inactivating airborne bacterial spores and mycobacteria in full-scale studies. Atmospheric Environment 37, 405–419. References

24 CSIR Built Environment Architectural Engineering Research Group Dirk Conradie Faatiema Salie Geoff Abbott Jeremy Gibberd Lorato Motsatsi Nkhensani Baloyi Peta de Jager Sheldon Bole Thabang Molefi Tichoana Kumurai Sidney Parsons


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