Ventilation for Health Care Facilities: Principles,
challenges, measurements and optimisation
Presented by Faatiema Salief
CSIR Built Environment
Monday 25 July 2011
Overview of the presentation:
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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
The airborne transmission of TB
•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)
Illustration of particle dispersal when a person sneezes
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
TB Infection Prevention and Control
Administrative
Environmental
Personal
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?
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Ventilation as a solution for TB IPC
• 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
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Concepts of ventilation – The dilution principle
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Concepts of ventilation – The dilution principle
exhaust
inlet
The first air change removes 63% of potentially infectious droplets
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Concepts of ventilation – The dilution principle
exhaust
inlet
The second air change removes 84% of potentially infectious droplets
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Concepts of ventilation – The dilution principle
•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
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Concepts of ventilation – The airflow pattern
•Airflow should be from clean areas to “dirty” areas
•Contaminated air should be exhausted directly to the outside.
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Can we successfully achieve these ventilation
standards?
•Mechanical ventilation - ventilation rate, pressure cascading, thermal
comfort, etc.
•Airborne Infection Isolation Rooms (AIIRs)
•Filtration, exhaust design
•Maintenance
•Cost of an effective system?
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Can we successfully achieve these ventilation
standards in our resource constrained settings?
•Natural ventilation
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Can we successfully achieve these ventilation
standards in our resource constrained settings?
•Wind pressure and buoyancy forces
• Single-sided and cross-ventilation
•Stack effect
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Can we successfully achieve these ventilation
standards in our resource constrained settings?
•Natural ventilation – ventilation rates? pressure cascading? thermal
comfort?
•Maintenance?
•Costs?
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Lets apply these principles by looking at some
case studies
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Investigating solutions for home-based care
(CSIR 2011)
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Investigating solutions for home-based care,
CSIR 2011
•Typical subsidy house
•Where is patient most likely to be?
•Ventilation rates?
•Airflow patterns?
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Investigating solutions for home-based care,
CSIR 2011
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Investigating solutions for home-based care,
CSIR 2011
All windows closed
Bedroom 2 window open
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Investigating solutions for home-based care,
CSIR 2011
Cross-ventilation
Single-sided ventilation with crossventilation
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Investigating solutions for home-based care,
CSIR 2011
•All windows closed – 0.6 ACH
•Bedroom 2 window opened – 8 ACH
•Cross-ventilation – 17 ACH
•Single-sided ventilation with cross-ventilation – 7 ACH
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
Measurements and Instruments
•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
Ventilation for Health Care Facilities: Principles, challenges, measurements and optimisation
References
http://www.thinking-outside-of-the-square.com/blog/wp-content/2009/02/sneeze-k-171.jpg
http://www.topbulb.com/find/uv.asp
http://www.technilamp.co.za/Products/bUltraVioletb/GermicidalIrradiation/tabid/6412/Default.aspx
http://www.sciencephoto.com/images/download_lo_res.html?id=662201106
W Kowalski. Ultraviolet germicidal irradiation handbook. – UVGI for air and surface disinfection. Springer. 2009.
http://www.uvcomparison.com/uvscience.php
Department of Health and Human Services., Centers for Disease Control and Prevention., National Institute for Occupational
Safety and Health., 2009. 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., 2009. Natural Ventilation for the Prevention of Airborne Contagion. PLoS
Medicine 6:3, 0-11. www.plosmedicine.org .
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., 2007. Upper-Room Ultraviolet Light and Negative Air Ionization to Prevent Tuberculosis Transmission
PLoS Medicine 4:2, 309-317. www.plosmedicine.org .
Nardell, E.A., 2010. Progress in the Application of Ultraviolet Germicidal Irradiation. American Society for Photobiology.
Powerpoint accessed www.ghdonline .
Xu, P., Peccia, J., Fabian, P., Martyny, J.W., Fennelly, K.P., Hernandez, M., Miller S.L., 2003. 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.
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