Filtration and UV disinfection Synergy By: Normand Brais P.Eng, Ph.D. National Air Filtration Association NAFA TECH 2014, Kissimme, FL April 3 2014

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

1) Fundamentals of UV light UV-A (400-315 nm) Sun glasses UV-B (315-280 nm) Sun tanning UV-C (280-200 nm) Germicidal UV UV-V (200-30 nm) V = Vacuum : O2  O3

DNA : Watson and Crick 1953

Reproduction: a molecular copying machine

UV Sterilization mechanism: Dymerisation of Thymines pairs

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

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

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

2) Cooling Coils Surface Disinfection

Coil without adequate Filter

Coil with good Filters: is it clean ?

Samples taken on Clean Looking Coils

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

inert dust can’t grow and multiply !

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 = 1,024 20 times = 1 million + 30 times = 1 billion +

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

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 99.999% kill = 5 log and so on…

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

Just the tip of the iceberg…

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 ! !

Area ratio = 2 X Fins per inch X Coil thickness

Inter-Fins UV Propagation

Move away for better results

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%

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

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

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

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’’ 1 000 μW/cm2 4 Watt/ft2 16’’ < Coil ≤ 18’’ 2 000 μW/cm2 8 Watt/ft2

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

UV COIL DISINFECTION

10 ft x 10 ft Coil

Petri dish samples taken with UV ON

3) How Filters Work

Most Penetrating Particle size The MPP Chasm Most Penetrating Particle size

HEPA Filters: MPP Chasm

Filters MERV efficiency (source: NAFA)

4 - Filling the Chasm with UV

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.

UV can complete the job

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

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% ! !

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.

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.

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

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

Thank you !