Welcome
to the September 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.
If flu spreads mainly through close personal contact, how can UVC devices installed
in the HVAC system be of help? A.
Flu viruses that infect humans are spread mainly via respiratory excretions. Frequent
hand-washing and avoiding close contact provide an important measure of protection,
but these actions do not stop the spread of viral organisms that become airborne
through coughing and sneezing and recirculate through the HVAC system. Steril-Aire
UVC devices emit the most germicidal energy in the ultraviolet spectrum with the
highest output in the industry. This energy penetrates even the tiniest microbes
to destroy their DNA and RNA, killing or deactivating them. In this manner, UVC
stops more than 90 percent of flu viruses and other microbes with each "pass"
or air change. There are 4-5 air changes per hour in most commercial buildings,
and up to 15-20 air changes in health care facilities. With these air changes,
UVC reduces the number of microbes to a level significantly below what it takes
to infect most people. The
Centers for Disease Control (CDC) recommends increased air volume in buildings
to help dilute airborne contaminants as a preventive measure against pandemic
flu. In this situation, UVC becomes even more effective, since more microbes are
killed with each additional air change. We
are often asked, "Won't the air filters in my system take care of the
problem?" Good air filtration is an important part of every control strategy
because it helps to guard against a wide range of particulate contaminants. But
viruses are the smallest of parasites, ranging from only 0.02 to 0.3 micron in
size. Typical ASHRAE building air filters - even those with high efficiency ratings
(e.g., MERV 14, also known as 95 percent ASHRAE-grade) - are not effective at
this size range.
HEPA filters offer efficiencies from 99.97% to 99.999% on 0.3 micron
particles. They provide some efficacy at the top end of the viral particle size
range but can allow smaller viruses to pass through the system. Another problem
is that these organisms are not destroyed: They collect on the clean side of the
filter, and when the VAV system powers down, a reverse flow effect may cause viral
contaminants to escape upstream of the filter. UVC devices are often installed
opposite HEPA filters to stop these escaping organisms and to protect the filters
themselves.
In
reality, millions of facilities are not equipped with HEPA or even high efficiency
MERV filters. UVC devices can be installed in virtually any type of HVAC system,
including ones that can't accommodate high efficiency air filters, e.g., the
small packaged air handlers often found in schools, hotels and other public buildings.
UVC thus
offers greatly enhanced IAQ and infection control to all types of occupied spaces,
even those that only have low efficiency filtration. It is a strategy well
worth considering for your property as the next flu season approaches.
For further information, please visit the Steril-Aire web site.
Sincerely,
Robert
Scheir, Ph.D. President
and Chairman
Steril-Aire,
Inc.
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