Building Design and Engineering
Approaches to Airborne Infection Control
Tobias van Reenen
CSIR
This course has been supported by the President’s Emergency Plan for AIDS Relief (PEPFAR) through Centers for Disease Control &Prevention (CDC) under the terms of U2G/PS002710-02
OVERVIEW
• BACKGROUND
•
STANDARDS & LEGISLATION
• DESIGN
• MANAGEMENT
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BACKGROUND
BACKGROUND
LEGIONELLA:Mesophilic Bacteria naturally occurring in low numbers in
aquatic environments
• Thrives in man-made water distribution and storage
systems (20-50°C)
• ~ Half of the species cause Legionellosis
• Legionella Pneumophila is responsible for 90% of cases
• Within endemic regions, about 4% to 5%
of pneumonia are caused by L. pneumophila
-Robert-Koch-Institut
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BACKGROUND
BACKGROUND
LEGIONELLA PNEUMOPHILA:>70 °C
At 66 °C
At 60 °C
At 55 °C
50 °C
35 to 46 °C
20 to 50 °C
Below 20 °C
: Disinfection range
: Legionellae die within 2 minutes
: They die within 32 minutes
: They die within 5 to 6 hours
: They can survive but do not multiply
: Ideal growth range
: Growth range
: They can survive but are dormant
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BACKGROUND
BACKGROUND
LEGIONELLA PNEUMOPHILA:-
35 to 46 °C
20 to 50 °C
: Ideal growth range
: Growth range
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BACKGROUND
BACKGROUND
LEGIONELLA RISK ENVIRONMENTS
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Cooling towers and evaporative condensers
Hot and Cold water systems especially showers
Spa baths
Water Features / Fountains
Machinery Spray-Cooling Systems
Water misting systems
HVAC Systems
Emergency Showers & Fire Hoses
Sprinkler systems and hose reels
Portable room humidifiers
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BACKGROUND
BACKGROUND
Biofilm:a thin layer of microorganisms adhering to
the surface of a structure, which may be organic or
inorganic, together with the polymers that they secrete
–http://medical-dictionary.thefreedictionary.com
• Biofilm development can result in cyclical system
contamination, complicating trouble-shooting
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BACKGROUND
BACKGROUND
4 EASY STEPS TO CONTRACTING LEGIONELLOSIS
1.
2.
3.
4.
Contamination & Colonisation of Water Systems
Growth & Proliferation
Aerosolisation
Inhalation Exposure (Duration x Susceptibility)
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STANDARDS & LEGISLATION
STANDARDS &
LEGISLATION
SOUTH AFRICA:• Occupational Health and Safety Act, 1993 Regulations For Hazardous
Biological Agents – pg24
• SANS 11731: - Detection and enumeration of Legionella
• Act No. 36, 1998 National Water Act
• Act No. 108, 1997 Water Services Act
• SANS 893 (1&2) Risk Management and Control of Legionella in Water
Systems (Committee Draft for Comment)
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DESIGN
DESIGN
• Biofilm colonises stagnant or low-flow water
in piping.
• Legionella risk increases with over-supply of
Hand Wash Basins
• Over-use of alcohol based hand sanitizers
= stagnation in unused basins (Dead Legs)
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WHO Supplementary Training Modules: Validation,
Water, Air Handling Systems - Water for Pharmaceutical
Use (Part 2): Water Purification Engineering
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• A “dead leg” is a leg length >2x the
diameter of the piping.
DESIGN
DESIGN
• Avoid “dead legs” in distribution piping
and fittings.
• Point-of-use “RO filters” ?
• Filters eradicate concentrate
organisms
• Point-of-use carbon filters?
• Breading grounds for Bio-film
• Aerosolizing/ Low flow faucets?
• Increase inhalation risk
• Pillar taps?
• Open standing dead-legs
• Automatic Faucets?
• Internal bio-film
• Maintenance burden
http://www.shea-online.org/View/ArticleId/71/Electronic-Faucets-Unsafe-for-Use-inHigh-Risk-Patient-Hospital-Settings-Study-Shows-Automatic-Fauce.aspx
DESIGN
DESIGN
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• Avoid warm water circulation or
storage
• Keep COLD loops <20°C
• Keep HOT loops >55°C
• Avoid storing too much water
• Use of many smaller cisterns
reduces stagnation
• Avoid long pipe runs
• Longer runs =
• Greater heat gain in cold
water systems
• Greater heat loss in hot
water systems
• Cisterns should be insulated from
heat sources
DESIGN
DESIGN
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DESIGN
DESIGN
• Mixing devices should provide 55°C at
upper limit of range
• A geyser is the “gatekeeper” to your
distribution system.
• >55°C prevents colonisation of HW
systems.
• Geysers should be set to 60°C
• Solar geysers can fail to maintain >45°C
year round.
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MANAGEMENT
• Identify Risks
• Hygiene risks
• Safety risks (>55°C water)
• Operational protocols
• Thermostatic mixing
• Define competency and responsibility
(Hygiene & Safety)
• Planners,
• Designers &
• Operators
• Implement program
MANAGEMENT
1. Risk Assessment and Management Plan
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MANAGEMENT
• Poor Water Supply Quality?
• Dispersive Disinfection
• Chlorination
• Free Chlorine
• Chloromines
• Chlorine Dioxide
• Silver & Copper ionisation
• Thermal Pasteurisation
• Site Disinfection
• Ozone & UV
• Not effective with downstream
colonies
MANAGEMENT
2. Disinfection
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MANAGEMENT
3. Maintenance and Cleaning
MANAGEMENT
• Develop and Implement Cleaning program
• Maintenance Policy
• Record keeping
4. Training, Monitoring and Review
• Training & Skills Matrix
• Develop monitoring program
• Updated asset register
• Effective logbook
• Engineering Change Control
• Safety and Hygiene Risks
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REFERENCES & FURTHER
READING
• http://www.ecosafe.co.za/legionella-background-information
• Water Systems: HTM 04-01 The control of Legionella , hygiene, “safe”
hot water, cold water and drinking water. Part A & B
• ASHRAE White Paper : Position Paper on Legionellosis, 1995
• World Health Organization – Legionella and the Control of Legionellosis
– 2007 – ISBN 92 4 156297 8
• SANS 893 (1&2) Risk Management and Control of Legionella in Water
REFERENCES
Systems (Committee Draft for Comment)
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