1. NAFA Guide To Air Filtration
Fifth Edition
Chapter 14
Ultraviolet Germicidal Irradiation Photocatalytic Oxidation
presented by the
National Air Filtration Association

2. Different Bands of UV
UVGI is not a new technology. First used in the early 1900 to disinfect water, it is best known for its use in upper-room irradiation during the Tuberculosis outbreak of the 1950’s. The newest application was to install lights in ductwork and thus kill organisms in a moving airstream.
UV-A known as “blacklight” and is used extensively in illuminating everything of injuries to the eye to law enforcement highlighting of human blood on object.
UV-B is used in tanning booths. UV in the wavelength of produce varying levels of ozone which some call “cold-cathode” ozone. Please understand that ozone as a molecular chemical is 03 in any form and is not recommended for use where people are in a space. Most all UVGI lamps are shielded from producing ozone.

3. UVGI-Range nm
This shows the range in which UVGI uses to inactivate airborne microorganisms – 200 to 280 nanometers.

4. Installed on upstream side of coils

5. Typical UVGI Lamp Location
While early work with UVGI in ductwork was hampered by varying temperatures, modern lamps have overcome this problem. This illustration shows the different installation locations for UVGI lamps to do different types of inactivation.

6. How it Works DNA of microorganisms absorb UVGI energy
Absorption of UVGI “dose” breaks the DNA strand

7. Dose on the DNA Chain
Microorganisms have DNA just like every living cell, and the “dose” of UVGI breaks the DNA chain very much like taking a zipper and removing a tooth. The microorganism cannot reproduce and this is how UVGI deactivates the organism.

8. k values: Susceptibility of microbes to UV
Figure 2. General ranking of suceptibility to UVC inactivation of microorganisms by group.
UVGI does have a higher effect on the vegetative bacteria and a lesser effect on fungal spores. Still, all organisms are affected by UVGI.

9. UVGI Can Fill-in the Most Penetrating Particle/Organism Size (MPPS) Gap
UVGI can inactivate that portion of the most penetrating size particles that filtration might miss, giving complete coverage to the range of microorganisms sizes.

10. UVGI Warning
UV lights have several properties that make them hazardous to human skin and eyes
Skin – Erythema, is a redness of the skin caused by capillary congestion like a sunburn
Extended exposure to UVGI lamps on the skin causes a capillary breakdown in the skin similar to a sunburn.

11. UVGI Warning
Eyes - Conjunctivitis (commonly called "Pink Eye") is an inflammation (burn) of the conjunctiva which is the the outermost layer of the eye and the inner surface of the eyelids
Looking directly at UVGI light can cause photokeratitis in the form of conjunctivitis. This feels like “sand in the eyes” and usually goes away within hours.

12. UVGI Warning - Materials
UVGI can breakdown components in an HVAC system:
Electrical wiring – plastics of all kinds
Filters - synthetic media
Insulation - open-cell foam
Clear plastic – become brittle over time
Please note items that are a problem for UVGI especially synthetic filter media exposed to UVGI. Services of UVGI lamps should always involve turning off lamps prior to opening lamp compartments.

13. Summary Just like air filters: UVGI must be installed correctly
UVGI must be maintained correctly
UVGI combined with air filtration provides an effective two-part particulate removal and microorganism inactivation system
In summary, UVGI is a technology that has matured in its application of in-duct HVAC. Combined with filtration, UVGI can help inactivate microorganisms that may grow in an HVAC system drain pan, on coils and in ductwork.

14. Sample Questions
UVGI is most effective on microorganisms in what range of the light spectrum?
200 to 280 nanometers
Why should UVGI lights be installed downstream of filters?
UV light can destroy certain types of filter media material
What should technicians do before servicing units in which UV lights have been installed?
Turn off lights prior to opening compartments where lights are located.

15. Photocatalytic Oxidation (PCO)
PCO uses ultraviolet radiation to promote molecular reactions and release of molecules from a catalyst such as titanium dioxide, zirconium dioxide or and aluminum oxide semiconductor. nm

16. PCO
When PCO technology is installed in a moving airstream, the process has the advantage of low pressure drop and reaction at ambient temperatures, causing a chemcial reaction with the contaminant. The process of PCO is the release of OH (hydrogen and oxygen molecules) from the catalyst surface. This reacts with and bonds with chemical contaminants in the air to form new compounds. The complete oxidation of VOC for example is carbon dioxide and water – CO2 and H2O (note, please use this chemical formula so they know it not just by the words but the chemical symbols).

17. Types of PCO Reactors
Here are the different styles of PCO reactors…don’t be thrown by the word “annular” as it just means the reactor is round in shape…

18. Types of PCO Reactors
The packed-bed reactor design uses glass beads that have coated with titanium dioxide and this gives the reactor a greater surface exposure area.

19. Types of PCO Reactors
The box reactor has the largest surface area using two fiberglass filters coated with titanium dioxide placed on either side of a UV light.

20. Types of PCO Reactors
Flat Bed reactors again use a fiberglass filter but also adds a pane of quartz to help correct variations in UV light exposure and intensity.

21. Summary
PCO is an immerging technology for cleaning the air of volatile organic compounds
Complete PCO reduces contaminants to CO2 and H2O – (carbon dioxide and water)
PCO adds little pressure drop to the system
In summary, PCO is a technology that allows for the destruction of contaminant compounds into harmless compounds and does not add large amounts of resistance to the HVAC system. A disadvantage of PCO may be the higher initial cost of the equipment versus using standard methods of molecular removal.

22. Sample Questions A drawback of PCO may be the?
High initial cost of equipment
PCO has how many types of reactor configurations?
Four
A PCO advantage is it’s?
Reaction at ambient temperatures/ small addition of resistance to the HVAC system/ complete destruction of contaminant into harmless elements

23. Thank you.
Other Questions?