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potentially persist on fomites anywhere from a couple of
hours up to nine days. However, it should be noted that there
are no documented cases to date of a coronavirus infection
originating from a fomite. There is, however, preliminary data
demonstrating the presence of SARS-CoV-2 in stool, indicating
that transmission can potentially occur through the fecal-oral
pathway. While transmission of coronavirus has only been
documented through respiratory droplet spread and not through
deposition on fomites, steps should still be taken to clean
and disinfect all potential sources of SARS-nCoV-2 under the
assumption that active virus may be transmitted through these
abiotic surfaces.
Previously, it has been confirmed that SARS can be, and is
most often, transmitted through droplets. Based upon previous
investigation into SARS, spread through aerosolisation remains
a potential secondary transmission method, especially within
the BE that contain heating, ventilation, and air conditioning
(HVAC) units. Mitigation of viral transmission through BE
air delivery systems is most often reliant on inline filtration
media. Residential and commercial systems typically require
a minimum efficiency reporting value (MERV) of 8, which is
rated to trap 70-85% of particles ranging from 3.0-10.0 microns,
a strategy employed to minimise impacts to cooling coils and
other HVAC equipment.
Higher MERV ratings are required in these settings to
filter incoming outside air based on local outdoor particulate
levels. Protective environment rooms in hospitals require the
most stringent minimum filtration efficiency. A MERV 7 or
greater is required as a first filter before heating and cooling
equipment, and a second high-efficiency particulate air (HEPA)
filter is placed downstream of cooling coils and fans. HEPA
filters are rated to remove at least 99.97% of particles down
to 0.3 microns. In most residential and commercial buildings,
these are often MERV -5 to MERV -11, and in critical healthcare
settings, MERV -12 or higher and HEPA filters are used.
MERV -13 filters have the potential to remove microbes
and other particles ranging from 0.3-10.0 microns. HEPA
filters are also able to filter out particles 0.3 microns and
larger. Most viruses, including coronaviruses, range from
0.004 - 1.0 microns, limiting the effectiveness of these
filtration techniques against pathogens such as SARS-
CoV-2. Furthermore, no filter is perfect. Recently, it has been
found that gaps in the edges of filters in hospitals has been
a contributing factor of the failure of filters to eliminate
pathogens from the shared air environment.
In recent years, the sharing economy has created
environments where multiple people share the same spaces.
It is possible that infectious disease transmission may be
impacted by this shift to the sharing economy. Shared
workspaces such as co-work environments, rooms in homes,
www.hvacronline.co.za
cars, bikes, and other elements of the BE may increase the
potential for environmentally mediated pathways of exposure.
In cases where alternate modes of transportation were
previously single occupancy vehicles, these trips are now often
replaced with rideshare programs or transportation network
companies, the potential for exposure may increase.
CONTROL AND MITIGATION EFFORTS IN THE BE
The spread of COVID-19 is a rapidly developing situation, but
there are steps that can be taken, inside and outside of the BE, to
help prevent the spread of disease.
Within the BE, environmental precautions that can be
taken to potentially prevent the spread of SARS-CoV-2 include
chemical deactivation of viral particles on surfaces. It has been
demonstrated that 62-71% ethanol is effective at eliminating
MERS and SARS. This ethanol concentration is the same as most
typical alcohol-based hand sanitisers, suggesting that properly
applied hand sanitiser may be a valuable tool against the spread
of SARS-CoV-2 in the BE. Items should be removed from sink
areas to ensure aerosolised water droplets do not carry viral
particles onto commonly used items, and countertops around
sinks should be cleaned using bleach or an alcohol-based cleaner
on a regular basis. RACA
Part 2 will be published in the next issue of RACA Journal.
•
Source: 2019 Novel Coronavirus Outbreak: A Review of the
Current Literature and Built Environment Considerations to
Reduce Transmission
ABOUT THE REPORT
Documented by Dr Walter Hugentobler, this literature review
gives valuable information for building operators on actions
they can take to mitigate the spread of COVID-19.
Alongside the regular advice we hear from governments
on hand washing and social distancing, its finding show that
increasing air exchange rate, maintaining indoor humidity
at 40-60%RH (not achievable in winter without active
humidification) and increasing natural light can all play a
positive role.
The scientific studies referenced in the literature review
provide valuable insight into how we can create a healthier
built environment, not just at a time of crisis but in our
everyday lives. For instance, if hospitals and public places
kept their indoor humidity at the recommended 40-60%RH,
many lives would be saved every year from reduced flu
transmission alone.
RACA Journal I May 2020
45