Going Green NRG

Industry News
4.2.2020
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“Anywhere you put thousands of people in close proximity, be it a hospital, airport, large office building or college, it’s advisable to try to eliminate disease transmission as much as possible…”
– Director of Facilities at Schenectady College, Alan Yauney

AIRBORNE VIRUSES
1. Can Light Destroy Covid-19?
2. Does UV light slow down the spread of viral infections?
3. Can COVID-19 spread through HVAC ducts?

AIRSTREAM DISINFECTION
4. How does germicidal UV-C “On-The-Fly-Kill” work?

1. Can Light Destroy Covid-19?

Coronavirus Pandemic took us all by storm- A viral infection so powerful its effects have spread across the world all at once. UVC News (https://uvcnews.com) touched on the connection between UV light and its defense against Covid-19. It was revealed that “Metropolitan Transit Authority (cbsnews.com) better known as MTA , “invested $1 million in ultraviolet light machines” (Spectrum News/NY1.com) to exterminate the airborne viral bacteria from Covid-19. New York City has implemented the use of UVC to kill Coronavirus in all forms of Public Transportation-a dangerous war zone for Covid-19 along with all indoor spaces. Thousands of experts, doctors, and research scientists back-up the theory of the UVC light method as the new solution to killing off bacteria and virus-deeming it impossible to reproduce.

2. Does UV light slow down the spread of viral infections?

A highly credible source interviewed by the “New York Times” who goes by the name Dr. Edward Nardell, has years of expertise in public health and social medicine. A professor at Harvard Medical School, Dr. Nardell goes on to mention his studies on coronavirus vs. UVC light. Ultraviolet light is transmitted through what we know as fluorescents. Ultraviolet light is the indoor artificial source of light that mimics the effects of outdoor ultraviolet light- light from the sun. Nardell adds “ceiling fans are sometimes installed to draw air upward so that floating bacteria, viruses, fungi are zapped more quickly.” (http://nytimes.com) It’s almost safe to say that this widely tested Covid killer will be in our future. It’s suggested that the frequency of UVC light is what sets it apart from UV light.

3. Can COVID-19 (or other viruses) spread through HVAC ducts?

It seems to go without saying however our world may need a gentle reminder about the amount of harm viruses like Covid, and others alike. With the strength of this strain of viral bacteria Covid-19 transmitted through anything-air ducts, fresh air, interior spaces, on clothing, It is suggested that every type of energy, unseen and seen is not invincible to the bacteria and potential virus of Coronavirus have found the COVID-19. Imagine every broken up particle emitted, carried around everywhere we go as much as our energy combined. Covid-19 and even common viral infections remains in the air for days at a time . It’s suggested that HVAC systems can, inadvertently, broadcast the infection and amplify its spread. Facility managers should consider employing both upper-air UVGI and in-duct or coil HVAC germicidal fixtures to ensure the greatest mitigation practical for controlling microbes and airborne microorganisms in communal spaces.

UVC’s ability to clear away contamination the air flowing through a building’s HVAC system can be most beneficial where diseases and illness is vulnerable, such as office buildings, schools/universities, healthcare settings, even something as simple as a movie theatre. An HVAC that is not thoroughly maintained in any public or private environment, disease is quickened. An HVAC that is not well taken care of is how germs recirculate through, which is essentially the thing that makes us susceptible to disease.

4. How does germicidal UV-C work?

Germicidal UV-C systems are installed in air conditioning, air-handling units to inactivate microorganisms and disinfect moving airstreams — as well as on HVAC surfaces. Germicidal UV-C kills up to 90% or more of all microorganisms living on HVAC air ducts and evaporator coils, depending on the lamp intensity and the length of exposure.

The operational factors that most directly impact airstream disinfection rates are:

  • Time/Intensity. The volume and velocity of air traveling through an HVAC system significantly impact the length of exposure to the germicidal wavelength (residence time)—a higher volume of air and/or faster-moving air requires greater intensity (more UV-C lamps).
  • Lamp location. Because cold air reduces the output of UV-C lamps and high RH affects pathogen susceptibility to UV-C, on-the-fly airstream disinfection applications are more effective when installed on the upstream side of the coil. In fact, moving UV-C lamps from 55-degree temperatures (typical of downstream) to 75-degree (typical of upstream) can increase a UV-C lamp’s output by 40%. On-the-fly disinfection can be accomplished downstream of the coils; however, this would require an increase in UV-C intensity (i.e. more lamps).
  • Reflectivity. UV-C energy’s effectiveness is multiplied (see chart) as it bounces off of the top, bottom, and sides of a plenum surface. Certain surfaces like aluminum can allow more UV-C energy to reflect and “stay in play” versus being absorbed by the surface. Most cooling coil fins are made from aluminum, which also assists in overall reflectivity.

Upstream/Downstream of Coil
For example, to keep cooling coils free from mold and bacteria, lamps might be installed on the downstream side of a coil surface, spaced every 30- to 40-inches of coil height (this equates to roughly 7.5 lamp watts per square foot). Here, since the coil is stationary, the exposure time to UV-C is 24/7/365, so the UV-C intensity can be lower.

However, for a moving airstream, UV-C intensity must increase significantly due to the decrease in time that the potential pathogen will be exposed to the UV-C energy. Greater UV-C dosage can be achieved by increasing the number of lamp watts per square foot (this equates to roughly 30 lamp watts per square foot on the downstream side of the coil). This can be accomplished by using “fixtureless” UV-C systems for 360-degree irradiation and/or decreasing lamp-row-spacing, for example, to 12-inch centerlines of coil height. When designing an “on-the-fly” kill application, we recommend modeling the intended design to ensure adequate germicidal dosage.

Sources:
1-https://fas.org/irp/doddir/army/pam385-69.pdf
2-https://www.ncbi.nlm.nih.gov/pubmed/20569852
3-https://www.ashrae.org/File%20Library/About/Position%20Documents/Airborne-Infectious-Diseases.pdf
4-https://www.cdc.gov/niosh/docs/2009-105/pdfs/2009-105.pdf?id=10.26616/NIOSHPUB2009105
5-https://www.researchgate.net/publication/284691618_SARS_Coronavirus_UV_Susceptibility
6-https://www.medrxiv.org/content/10.1101/2020.03.09.20033217v1.full.pdf

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