(Issue: February 2021)
Germicidal UV Applications
By Bernard J. Erickson, CLMC, LC, CLEP, MBA, IES Emeritus, Executive Vice President, Facilities Solutions Group
Prior to COVID-19 most applications for GUV centered on hospitals and medical facilities. Since March 2020, however, end users are utilizing GUV in schools, offices, hospitality, restaurants, and other applications. The consensus is that regardless of a vaccine for COVID -19, disinfecting air and spaces will remain a concern for years to come. As the Centers for Disease and Prevention (CDC) has stated from the outset of the pandemic, the best solutions will involve multiple means of disinfection and protection. These will likely include GUV, chemical disinfectants, the use of masks, HEPA filtration and other technologies. While it is impossible to provide 100 percent germ-free environments while spaces are occupied (since occupants can constantly be re-infecting spaces), GUV solutions can be part of a what I like to call a Constant Viral Load Reduction (CVLR) program.
Portable Units Versus Permanent Fixtures
Initial interest has been high for portable UVC disinfection units. They allow end users to leverage their spend using the same fixture for several rooms, or moving the portable unit to different locations in a larger space in order to provide complete disinfection. Portable units come in a variety of sizes, from small 38W tabletop units suitable for disinfecting small areas to large 1,000W carts that can disinfect 20,000 square feet of open space in 60 minutes. There is a linearity to the power of the unit, the amount to invest, and the time it takes to disinfect a space.
Time Vs. Money
When comparing a GUV solution to chemical disinfection, compare the upfront cost of GUV equipment to the ongoing cost of chemicals. Disinfectants can be much more expensive than cleaners, costing as much as $8.00 a gallon. In addition, consider the labor to apply the disinfectants, estimated to be 350-400 square feet an hour. But once a path is decided to utilize GUV, it is important to balance the capital budget to purchase GUV equipment versus the manpower to operate the equipment that has been purchased.
Whether using permanently mounted fixtures or portable disinfection units, specification of the proper solution that will inactivate 99.99 percent of viruses and bacteria is a combination of UV intensity, irradiance distribution, and delivered UV dosing to all areas that are to be disinfected. Based on the product specified, there is a need to confidentially be able to recommend the run time for a specific room required to eliminate the pathogens in a space.
A Classroom Example
The following example will look at solutions to disinfect a typical school classroom. The examples illustrate the ability to choose different solutions to accomplish the same task, each requiring different capital and labor investments.
Permanently Mounted Fixtures using 254nm UV
One option would be to install 2X4 grid troffers utilizing four GUV lamps, each producing 117 uW/cm2 for a total UV irradiance of 468 uW/cm2. As seen here, if two fixtures are installed in the classroom, the space can be disinfected in five to 10 minutes. While some surfaces, such as the desk directly beneath the fixture are disinfected in a minute, the fixtures need to be kept on for 10 minutes in order to expose the areas receiving the lowest exposure to the required 5mj/cm2 that has been shown to deactivate SARS- COVID-2. These fixtures could only operate when the space is vacant and would require a safety control system as well to insure it would not operate when the room is occupied.
To illustrate the linearity previously discussed, if the number of fixtures are reduced from two to one, it is now taking twice as long, or 20–25 minutes to disinfect the space.
Permanently Mounted Fixtures using 222nm UV
Another fixture option would be to install 222nm or far-UV fixtures. Initial studies have shown that far-UV does not penetrate human or animal skin or eyes, so fixtures could provide continuous disinfection of occupied spaces. Using five fixtures can obtain a very comprehensive disinfection that is continuous all day as the space is occupied. Installed cost is higher than 254nm due to the additional fixtures required, but other options can include just one fixture over the teacher for partial area disinfection.
Portable Carts using 254nm UV
Portable carts offer a way for end users to leverage their capital spend, since a portable cart can do multiple rooms. However, labor costs increase since the cart needs to be moved from room to room, and even within the room. With carts there is the option of investing in more powerful units that can disinfect a space more quickly. But of course, these units cost more money. In the example pictured the standard 300W cart produces 640 uW/cm2. It would disinfect the classroom in one hour and would need to be moved across the room after 30 minutes. The more powerful 300W Plus unit produces more than twice the amount of UV irradiance as the standard unit but would still need to be moved across the room once for the quickest disinfection time.
Upper Air Disinfection
Another way to deploy UVC in a room would be to install upper air disinfection fixtures. These fixtures use UVC lamps that deactivate pathogens and viruses in the air while to room is occupied. Unlike direct UVC irradiance, upper air units disinfect air only. They do not disinfect surfaces. The UVC lamps are angled up to the ceiling so they do not irritate the skin or eyes and create a disinfection zone. Air is naturally circulated through the zone through convection. In the case of the 20X25 classroom we could utilize two, 4-foot GUV fixtures, each having 1 lamp producing 115 uW/cm²
Restrooms are always a concern where germs and pathogens are concerned. Stalls and dividers create obstacles for UVC irradiance, often necessitating the installation of multiple fluorescent style UVC fixtures. This added load can sometimes require additional wiring and capacity. Pulsed xenon UVC fixtures can be a good option here. Pulsed xenon uses a powerful, broad-spectrum light, including germicidal UV-C, UV-B and anti-bacterial UV-A to optimize germ-killing efficiency. The restroom below requires two fixtures consuming 100 watts to disinfect the space in 30 minutes.
UVC can be used to disinfect transportation vehicles such as school buses and ambulances. This is where portable carts come in handy, serving the dual purpose of disinfecting inside your building, and then being deployed in mobile applications as well. The standard 300W cart used in a school classroom can be deployed to disinfect school buses. As shown below, a single 300W cart can disinfect a school bus in 30 minutes, with two steps.
The same holds true for an ambulance. The same 300W cart can disinfect an ambulance in five to 10 minutes. There is also the option to permanently mount fixtures in these vehicles as well. If far-UV (222nm) technology is used, the system could be used while the ambulance is occupied, providing 90 percent+ upper air disinfection within minutes, 90 percent surface disinfection within 15–20 minutes and 99.9 percent surface disinfection within one hour.
Houses of Worship
Disinfecting larger open spaces, such as churches and temples is certainly important these days, with the larger groups of people that assemble there. It can also be challenging since the spaces are often sizeable, and time can be of the essence between services. This is a good example of where the additional investment in a larger wattage cart can make a lot of sense. In the example below, a 100’X100’ sanctuary is disinfected in one hour, moving a 1000W portable cart six times to six different locations. This process would literally take all day with a smaller cart. Additional protection could be provided by installing upper air disinfection units to help clean the air while the church is occupied, reducing the viral load between operations of the 1000W cart.
Ballrooms and Arenas/Exhibit Halls
Another large open space where larger groups of people congregate would be exhibit halls and arenas. Here again the 1000W cart is a great choice. The 1000W cart has 4006 uW/cm2 of UVC intensity, more than six times the intensity of a standard 300W cart.
As shown in the illustration, an empty ballroom or general meeting space could be disinfected in 20 minutes, moving a 1,000W cart once. If the space were filled with chairs, then a longer run time, and potentially additional steps would be required. An arena or trade show floor could also be sanitized. The example below shows an empty area being sanitized in just over an hour with nine steps.
But what if the arena or ballroom was set up for a trade show? UVC is a great solution here, sanitizing not just the air and surfaces of tables, railings and chairs, but booths and other areas as well. But based on the many obstructions in the space, there would be many required steps or movements of the cart. This is where an automated disinfection robot can significantly reduce labor costs. Different robots work in different ways. Some can be incredibly expensive and quite complex. But the simplest versions can be “trained” to follow a route and automatically disinfect a space during off-hours when it is vacant or closed to the public.
In the arena example above the training process would entail walking the robot (via joystick) to each disinfection point, setting the run time and then saving the program. The unit could then be programmed via a cloud-based app to run through the arena and then shut off. If an unexpected object is encountered sensors would avoid it and go around it if possible. If the route is totally blocked, the robot will stop. A cloud-based program will also record the disinfection route and dosage on a map so that you can verify and maintain a record of disinfection.
These are but a few of many examples of how GUV can play a critical role in providing Constant Viral Load Reduction in the battle against COVID-19 and help keep us all safe against pathogens and bacteria in the future.
About the Author
Bernie Erickson is executive vice president of Facilities Solutions Group and has over 40 years’ experience in the lighting and electrical industry. He has been a member of the Board of the National Council on Qualifications for the Lighting Professions (NCQLP) for 13 years and currently serves as its president.
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