1. Filtration and UV disinfection Synergy
By: Normand Brais P.Eng, Ph.D.
National Air Filtration Association
NAFA TECH 2014, Kissimme, FL
April

2. Content
1) UV Fundamentals 2) Cooling Coils Disinfection 3) Filtration Fundamentals 4) Filtration + UV : complementarity

3. 1) Fundamentals of UV light
UV-A ( nm) Sun glasses
UV-B ( nm) Sun tanning
UV-C ( nm) Germicidal UV
UV-V ( nm) V = Vacuum : O2  O3

4. DNA : Watson and Crick 1953

5. Reproduction: a molecular copying machine

6. UV Sterilization mechanism: Dymerisation of Thymines pairs

9. Fundamental Principle of UV disinfection
UV Dose = intensity x time
joule/ m2 watt/m sec
The larger the Dose,
the more alterations to the DNA,
leading to Sterilization

10. Direct Mathematical Correlation
N0 = Initial number of micro-organisms N(t) = Number of micro-organisms surviving at time “t” I = UV radiation intensity in W/m2 t = exposure time in seconds Dose = I x t, in Joule/m2 K = susceptibility coefficient in m2/joule

12. k values: Susceptibility of microbes to GUV
Figure 2. General ranking of suceptibility to UVC inactivation of microorganisms by group.

13. 2) Cooling Coils Surface Disinfection

14. Coil without adequate Filter

15. Coil with good Filters: is it clean ?

16. Samples taken on Clean Looking Coils

17. Difference between virus, bacteria, fungi and inert mineral dust ?

18. inert dust can’t grow and multiply !

19. About multiplication…by 2 2 x 2 x 2 x 2 x…. x 2 =
About multiplication…by 2 2 x 2 x 2 x 2 x….x 2 = ? 10 times = 1, times = 1 million + 30 times = 1 billion +

20. What lives on cooling coils ?
A) Mold spores UV Dose for 90% kill
Aspergillus Niger D90= 448 mJ/cm2
Cladosporium wemecki D90= 448 mJ/cm2
Penicillium D90= 224 mJ/cm2
B) Bacteria
Legionella Pneumophilia D90= 2.5 mJ/cm2
Pseudomonas Aeruginosa D90= 2.2 mJ/cm2

21. UV dose required against Aspergillus and Cladosporium
UV Dose: 448 mJ/cm2 for 90% kill = 1 log UV Dose: 896 mJ/cm2 for 99% kill = 2 log UV Dose: 1344 mJ/cm2 for 99.9% kill = 3 log UV Dose: 1792 mJ/cm2 for 99.99% kill = 4 log UV Dose: 2240 mJ/cm2 for % kill = 5 log and so on…

22. How much UV does it take to keep a coil clean ?
Disinfecting Aspergillus at 99% within 1 hour requires a UV intensity of : Intensity = 896 mJ/cm2/(3600 sec) = 0.25 mW/cm2 = 250 μW/cm2

23. Just the tip
of the iceberg…

24. Coil heat transfer surface –vs- face area
Example :
coil of 10 ft x 10 ft
10 inches thick, 10 fins/inch
Coil face = 100 ft2
Total coil surface = 20,000 ft2 ! !

25. Area ratio = 2 X Fins per inch X Coil thickness

26. Inter-Fins UV Propagation

27. Move away for better results

28. Inter-Fins UV Propagation
1 reflection : UV = 80% 2 reflection : UV = 80% x 80%= 64% 3 reflection : UV = 80%x80%x80%= 51% 4 reflection : UV = 80%x80%x80%x80%= 41% 5 reflection : UV = 80%x80%x80%x80%x80%= 33% 6 reflection : UV = 80%x80%x80%x80%x80%x80%= 26% 7 reflection : UV = 80%x80%x80%x80%x80%x80%x80%= 21% 8 reflection : UV = 80%x80%x80%x80% x80% x80% x80% x80%= 17% 9 reflection : UV = 80%x80%x80%x80%x80%x80%x80%x80%x80%=13% 10 reflection : UV = 80%x80%x80%x80%x80%x80%x80%x80%x80%x80%=11%

29. Aspergillus Niger: time to reach 99% disinfection inside a Coil
At Coil face, 250 μW/cm2: 1 hour At 2’’ depth, 113 μW/cm2: 2.2 hours At 4’’ depth, 51.4 μW/cm2: 4.9 hours At 6’’ depth, 23.3 μW/cm2: 11 hours At 8’’ depth, 10.6 μW/cm2: 24 hours At 10’’ depth, 4.8 μW/cm2: 52 hours At 12’’ depth, 2.2 μW/cm2: 115 hours At 14’’ depth, 1.0 μW/cm2: 254 hours At 16’’ depth, 0.45 μW/cm2: 561 hours

30. Aspergillus Niger: time to reach 99% disinfection inside a Coil
At Coil face, 500 μW/cm2 : 0.5 hour At 2’’ depth, 227 μW/cm2: 1.1 hours At 4’’ depth, 103 μW/cm2: 2.4 hours At 6’’ depth, 46.6 μW/cm2: 5.4 hours At 8’’ depth, 21.1 μW/cm2: 12 hours At 10’’ depth, 9.6 μW/cm2: 26 hours At 12’’ depth, 4.3 μW/cm2: 58 hours At 14’’ depth, 2.0 μW/cm2: 127 hours At 16’’ depth, 0.9 μW/cm2: 281 hours

31. Aspergillus Niger: time to reach 99% disinfection inside a Coil
At Coil face, 1000 μW/cm2 : 0.25 hour At 2’’ depth, 453 μW/cm2: 0.55 hours At 4’’ depth, 205 μW/cm2: 1.2 hours At 6’’ depth, 93.1 μW/cm2: 2.7 hours At 8’’ depth, 42.2 μW/cm2: 5.9 hours At 10’’ depth, 19.1 μW/cm2: 13 hours At 12’’ depth, 8.7 μW/cm2: 29 hours At 14’’ depth, 3.9 μW/cm2: 64 hours At 16’’ depth, 1.8 μW/cm2: 140 hours

32. UV rules of thumb –vs- Coil Thickness
Coil thickness Avg UV on face Gross Power
Coil ≤ 12’’ 250 μW/cm2 1 Watt/ft2
12’’< Coil ≤ 14’’ 500 μW/cm2 2 Watt/ft2
14’’< Coil ≤ 16’’ μW/cm2 4 Watt/ft2
16’’ < Coil ≤ 18’’ μW/cm2 8 Watt/ft2

33. Coil Disinfection Elimination of biofilms formation
Lower pressure drop
better heat transfer
energy savings
Improved occupant’s wellbeing
UV system design criteria:
Intensity
Homogeneity
Inter-fin penetration

34. UV COIL DISINFECTION

35. 10 ft x 10 ft Coil

37. Petri dish samples taken with UV ON

38. 3) How Filters Work

40. Most Penetrating Particle size
The MPP Chasm
Most Penetrating Particle size

41. HEPA Filters: MPP Chasm

42. Filters MERV efficiency (source: NAFA)

43. 4 - Filling the Chasm with UV

44. FILTERS: good on small or large microbes
4) FILTER+UV SYNERGY
FILTERS: good on small or large microbes
Between 0.02 and 1 micron, filters efficiency drop
HEPA filters:
also a drop of efficiency between 0.1 and 0.4 micron
UV : efficient in this size range
viruses are easy targets for UV.

45. UV can complete the job

46. Example of Combined efficiency: MERV 16 Filter + UV ≥ HEPA

47. A proof by example : In-Vitro Fertilization Clinics
IVF clinics with best HEPA filtration
Fertilization success rate stagnated at 20 to 30%
When UV was added to HEPA
Success rate jumped at 70 to 85% ! !

48. Published by : THE LANCET Medical Journal
Independent Studies
Published by : THE LANCET Medical Journal
“Impact of Ultraviolet Germicidal Lights Installed in the Ventilation Systems of Office Buildings on Workers Health and Well Being”
Richard Menzies MD MSc1,2, Julia Popa BEng MEng1,
James A Hanley PhD2, Thomas Rand PhD3, Don Milton MD Dr. PhD4.
From :
1.Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute,
2.Department of Epidemiology and Biostatistics of McGill University
3.Dep’t of Biology, St. Mary’s University, Halifax, Nova Scotia,
4.Department of Environmental Health, Harvard School of Public Health, Boston.

49. The LANCET paper highlights
771 Employees from 3 office buildings participated in the study.
UV ON for 4 weeks
UV OFF for 12 weeks
3 cycles totalling 48 weeks.
Repeated twice, over 2 years.
When UV were ON :
40% reduction in respiratory symptoms
20% overall reduction in all symptoms
30% reduction in mucosal symptoms
These benefits were greatest for those with known allergies.

50. Conclusions
When properly engineered with adequate software, UV eliminates coil biofilms and saves Energy $$$
UV improves overall performance of filters
Just like for Filtration, UV Fundamentals are also well defined in ASHRAE Handbook

51. Working hand in hand with good filtration practice, a well engineered Ultraviolet system brings a boost to building hygiene and energy efficiency.

52. Thank you !