ASHRAE Journal - August 2013 - 52

technical feature

Shaping the Next…
Ultraviolet Germicidal Irradiation for Indoor Environmental
Quality
By Stephen B. Martin, Jr., p.e.

Ultraviolet germicidal irradiation (UVGI) technologies have existed for over a century. Today, UVGI
fixtures with low-pressure mercury vapor lamps are
commonly installed inside HVAC systems in schools,
office buildings, health-care settings, correctional
facilities, social-assistance shelters, and homes to
improve indoor air quality and reduce disease transmission. With the emergence of new and drug-resistant pathogens, and the continued threat of bioterrorism, it is likely that UVGI systems will be applied even
more in the future. However, the effective and efficient implementation of UVGI technologies remains
as much an art as a science.
Successful UVGI systems have been installed for a variety of applications, yet no consensus guidelines exist that
comprehensively address all aspects of system design
to ensure good disinfection. Important tools necessary
for establishing design guidance are also lacking. There
are currently no standard test methods for rating the
performance of typical in-duct UVGI devices. Similarly,
critical analyses of real-world systems that evaluate performance and economics are lacking. As a result, UVGI
systems are typically oversized to ensure performance,
which creates the potential for increased equipment and
utility costs, and wasted energy.

being applied in health care through the requirements
of the Hill-Burton Act. The most widely used high-end
commercial filtration was performed at that time by
elaborate electrostatic precipitation or exotic air washers. Chemisorbant molecular filters had just been patented and introduced to the industrial market. The 2 in.
pleated filter had been developed with proprietary fabrication technology. And, the 21st century was a career
lifetime away.
Here we are in the 21st century and, of course, those
original restrictive patents and cumbersome products
are long gone, allowing proliferation and maturing
of products, companies, and markets. However, the
latter period of the 20th century, including the last
decade, contributed significant factors that impact FAC
52

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Au g ust 2013

ASHRAE’s Standards Project Committee 185 has
developed two proposed test methods that have each
gone through public review and should be published
soon. Proposed Standard 185.1P, Method of Testing UVC
Lights for Use in Air Handling Units or Air Ducts to Inactivate
Airborne Microorganisms, was developed to test in-duct
UVGI devices for “on-the-fly” disinfection of organisms in the moving airstream. In-duct UVGI devices
used to inactivate microorganisms on coils, drain
pans, or other surfaces will be addressed by Proposed
Standard 185.2, Method of Testing Ultraviolet Lamps for
Use in HVAC&R Units or Air Ducts on Irradiated Surfaces.
Multiple research studies to critically analyze UVGI
system performance, energy use, and economics are
currently under way or planned to launch soon.
The important information that will result from
these test methods and research projects is coming at
a critical time. UV light-emitting diodes and amalgam
lamps already exist, and research to produce lamps
with non-toxic materials continues. Smart ballast
systems are being designed to switch lamps on/off and
maintain a set disinfection level as variables within
HVAC systems change. Closing current gaps in understanding of system design will provide engineers with
key tools that can be used as these exciting new technologies are incorporated into future UVGI systems.
Stephen B. Martin, Jr., p.e., Centers for Disease Control and prevention, national institute for
Occupational Safety and health, Division of respiratory Disease Studies, Field Studies Branch.
DISclaImEr: ThE STaTEmENTS IN ThIS arTIclE arE ThoSE of ThE aUThor aND Do NoT NEcESSarIly
rEprESENT ThE vIEwS of ThE NaTIoNal INSTITUTE for occUpaTIoNal SafETy aND hEalTh.

application and technology.
The 1989 version of ASHRAE Standard 62 incorporated
the Indoor Air Quality Procedure, which allowed the use
of FAC as an alternative to increased use of treated outdoor ventilation air for internal contamination control.
The development of the “mini-pleat” fabrication technology enabled high-efficiency and high capacity particulate filtration with lowered pressure drop.
The development of new synthetic polymer-based
fibers yielded filter media with electrostatic properties that enabled enhanced extraction efficiencies with
lower pressure drop.
The development of ASHRAE Standard 52.2 facilitated
more authentic particulate efficiency performance data
and replaced 70 year-old test methodology. Likewise,

ASHRAE Journal - August 2013

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