Welcome
to the February edition of Steril-Aire's UVC E-Newsletter. In each issue, we will
address an important question about ultraviolet-C or "UVC" devices for
building HVAC systems. Steril-Aire
will also be happy to provide you with a free on-site evaluation on how to equip
your building(s) for energy, mold, IAQ and infection control using UVC technology.
If you would like to know more, contact
us today. Q.
What is biofilm, and why is it a problem in air handling systems?
A.
Biofilms are present in everyday life. The plaque that can build up on teeth is
a form of biofilm, as is the material that clogs up household drains. Biofilms
are also widely prevalent in commercial air handlers. For example, a 4-ft x 6-ft
coil eight rows deep, with 10 fin rows per inch, has a total surface area of 5,000
sq ft plus the drain pan. That is a huge amount of surface area on which biofilm
can build up, leading to a range of IAQ and operational problems that are sometimes
mistakenly attributed solely to mold. Biofilms
may be composed of different microorganisms (bacteria, fungi, debris, et al) that
grow on surfaces in the presence of moisture, producing a gluey matrix that sticks
to the surface and develops attached communities. Life within the biofilm is protected
against penetration by most outside agents. According to the Montana State University
Center for Biofilm Engineering: "Microbial biofilms on surfaces cost the
nation billions of dollars yearly in equipment damage, product contamination,
energy losses and medical infections. Conventional methods of killing bacteria
(such as antibiotics, and disinfection) are often ineffective with biofilm bacteria."
Biofilm is, however,
proven to be susceptible to the germicidal effects of UVC light, which works by
attacking the DNA or RNA of the cells to kill or inactivate the microorganisms.
To keep coils clean and free of biofilm and other buildup, a high output UVC light
source should be positioned perpendicular to the fins of the coil and 12"
off the discharge coil face. When using high output lamps to eliminate contamination
from an existing system, a 24-inch centerline is recommended. With new systems,
the centerline may extend to 30".
Left:
Three months after chemical cleaning, biofilm has already grown all over this
coil. Right: Six months after installation of UVC, the same coil is clean and
free of biofilm.
Sincerely,
Robert
Scheir, Ph.D. President
and Chairman
Steril-Aire,
Inc.
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