1. Constraints, Measurement, and Maintenance
9/19/2018
UVGI:
Constraints, Measurement, and Maintenance
Sonya Milonova
Research Fellow
Harvard School of Public Health
July 9, 2015

2. Constraints
Measurement
Maintenance

3. Constraints High humidity thought to protect organisms
9/19/2018
Constraints
High humidity thought to protect organisms
Requires vertical air mixing
Low ceilings
Lack of guidelines, as well as education on proper dosing, installation, maintenance, etc.
Access to well designed fixtures
Meters (expensive and unavailable)

4. Constraints
Measurement
Maintenance

5. Measurement: Definitions
9/19/2018
Measurement: Definitions
Irradiance
UV energy flux reaching a flat surface
Units: watts/square centimeter (W/cm2)
Important in the lower room
Fluence rate
UV energy flux reaching a tiny spherical surface
Important in the upper room
Fluence: energy delivered per unit area

6. Measurement: Inverse Square Law
Describes the relationship between irradiance from a point source and distance

7. Measurement: Radiometers
9/19/2018
Measurement: Radiometers
Hand-Held Meters
International Lighting ( $1500)
Gigahertz-Optik
Flat sensor ( $2500)

8. Measurement Calibration
9/19/2018
Measurement
Calibration
Periodic (every 3-4 years) comparison against calibrated meter
Zero adjustment
Potential interferences
Fluorescent lights
Sunlight (even through windows)

9. Measurement Lower room:
9/19/2018
Measurement
Lower room:
Measurements in lower room (approx. 1.8 m from the floor) should not exceed a total dose of 6.0 mJ/cm2 over an 8 hour work day
Check places where occupants will spend most of their time (ie. beds in hospital ward)
Upper room:
Measurements above fixtures (2.4 m and above) should be as high as possible while maintaining safe lower room levels
Keep sensor horizontal (parallel to earth)
Swivel sensor 360° to find maximum reading

10. Measurement: 80° FOV tube
Threshold Limit Value specifies that the source needs to be measured over an angle of 80 degrees at the detector
Use a Field of View (FOV) tube attached to a UVC sensor for lower room safety measurements
Tests indicate the sleeve would reduce lower room measurements by 5-45% (depending on location)

11. Constraints
Measurement
Maintenance

12. Maintenance
Establish realistic maintenance and operation objectives during the design phase of the UVGI installation
Tasks:
Output measurements
Fixture and lamp cleaning
Routine inspections of fixture installations
Repairs
Important considerations:
Documentation
Communication

13. Emission Performance Initial decline during break-in period
Gradual decline over lifetime due to lamp solarization (frosting) and metal deposition on inner surface
Lamp failure:
Even if UV is hardly being emitted, might see blue light

14. Emission Performance Annual lamp emission decline observed:
9/19/2018
Emission Performance
Annual lamp emission decline observed:
Average 16% decline for linear tube lamps
Average 26% decline for folded (compact) lamps
Annual lamp failure observed (~9000 hours):
<1% for linear tube lamps
<2% for folded lamps
Continuous operation can extend reported lifetime by up to 60%

15. Emission Performance
After the fixture has been on for 100 hours, measure the baseline output:
Stand 1 m away, directly in front of center of fixture
Measure at height of fixture (use tripod)
Keep sensor horizontal (parallel to floor)
Direct sensor straight forward (toward fixture)
Find maximum
Record baseline output in logbook
Repeat every 6 months
Replace lamp when output = 70% of baseline
After the fixture has been on for 100 hours, measure the baseline output:
Stand 1 m away, directly in front of center of fixture
Measure at height of fixture (use tripod)
Keep sensor horizontal (parallel to floor)
Direct sensor straight forward (toward fixture)
Find maximum
Record baseline output in logbook
Repeat every 6 months
Replace lamp when output = 70% of baseline

16. Lamp Cleaning Frequency of cleaning is site specific:
3 month cleaning intervals for dusty, active areas
Annual cleaning intervals for most other areas
Clean lamps and reflective surfaces with gauze and cleaner containing 70% (or more) alcohol
Avoid touching the bare lamp with your hands
Use a multi-stranded polymer brush to clean between louvers

17. Inspections Initial inspection: Level with the earth?
Properly fixed to the wall/ceiling?
Pointing in the right direction?
Mounted high enough?
Routine inspection:
Is the lamp turned on?
Is it clean?
Check maintenance log

18. Fixture Repair
Establish defined, comprehensive replacement and repair agreement with vendors
Keep track of warranties
Receive advance replacements and use packaging for return and repair of defective or damaged fixtures

19. Communication Establish communication responsibilities
If a lamp burnout (or other problem) is observed, who notifies facility maintenance?
Once initiated, who is responsible for inspecting/ replacing the lamp?
If the individual responsible leaves the facility, how is the communication process altered?
UVGI maintenance and repair procedures should be incorporated into existing facility maintenance procedures

20. Cost of Maintenance Supplies/Equipment
Cleaning supplies (gauze, alcohol, brushes, etc.)
Replacement lamps and parts
Replacement of worn out or defective fixtures, including handling and shipping costs
Labor
Routine labor: fixture maintenance incorporated into routine physical labor; and/or
Dedicated labor: quarterly or annual maintenance tasks with labor per fixture established and budgeted

21. Maintenance Re-Cap
Maintenance strategies begin at the initial purchase of UVGI fixtures
Identify individuals responsible for maintenance
Replace lamps on rotating schedule; focus cleaning efforts on target zones
Keep clear maintenance logs and formally pass UV system maintenance responsibilities to new staff
Utilize the resources of the upper room UVGI research community to continue learning about UVGI research and operating experience

22. Coming Soon…
UVGI Disinfection of Room Air: An Evidence Based Guideline for Design, Implementation, and Maintenance
Specific for South Africa
Includes guidelines for UVGI dosing, fixture design, installation, verification testing, monitoring and maintenance, and much more!

23. Questions?
Special thanks to:
Thomas S. Dumyahn