The SARS-CoV-2 (COVID-19) pandemic has created an unprecedented demand for germicidal ultraviolet (UV) light irradiation equipment, marking a turning point for a previously underutilized technology in infectious disease control within buildings. For nearly a century, ultraviolet germicidal technology has effectively combated surface and airborne microbes, including tuberculosis, measles, and more. Historically, its applications were largely confined to high-risk locations like emergency rooms and surgical suites. However, in the wake of the COVID-19 outbreak, the landscape changed dramatically. Suddenly, various facilities sought methods for a safe return to normalcy, and their quest led them to upper-room ultraviolet germicidal irradiation (UVGI) as a promising strategy to mitigate infection risks.
An unpublished study by Fears et al. highlights that SARS-CoV-2 can retain infectivity when suspended in aerosol form for up to 16 hours. Concerns arise that these aerosols may be inhaled by individuals sharing the same room as an infected person. Positive swab tests taken from patient room exhaust outlets underscore the potential displacement of coronavirus-laden droplets through airflow.
With all recent studies suggesting that this coronavirus may linger in the air for extended periods of time, the need to disinfect the air is crucial. This idea of air disinfection reminds us of the powerful method we have long discovered in the past. And that is UV light.
Early successes in developing the upper-room UVGI system date back to the 20th century. In 1941, William F. Wells conducted a pioneering study to assess the effectiveness of this system in preventing the spread of measles among students in Philadelphia day schools. The results were striking: In schools without upper-room UVGI, 53.6% of susceptible students were infected. However, in schools equipped with upper-room UVGI, only 13.3% of susceptible students contracted the disease. This early research laid the foundation for subsequent efforts, such as those led by McLean during 1957-1958 to combat the flu pandemic. McLean’s endeavors demonstrated success as well, with an infection rate of only 1.9% in an irradiated ward compared to an 18.9% infection rate in a non-irradiated ward.
Upper-room or upper-air UV fixtures emit UV-C rays above individuals’ heads. These fixtures are strategically placed on walls within occupied rooms. Importantly, UV-C rays never come into direct contact with human skin or eyes, rendering them safe for continuous operation (when properly mounted). The diagram below illustrates how upper-air fixtures should function. They are suitable for buildings with ceilings that are at least seven feet high.
According to the CDC, UVGI effectively eliminates airborne pathogens within the room where they are released, and fixtures are installed to prevent direct UV exposure to occupants. The agency recommends UVGI for indoor spaces lacking mechanical HVAC systems, areas where year-round natural ventilation is challenging, crowded spaces like lobbies, restaurants, break rooms, cafeterias, and settings where mask removal for eating or drinking is common. It is particularly useful in high-risk indoor environments such as hospital waiting rooms and other areas frequented by individuals with illnesses. Furthermore, it aligns with efforts to maintain distance in situations where a six-foot gap cannot be consistently upheld.
As per ASHRAE’s “Position Document on Airborne Infectious Diseases,” upper-room UV must become a standard feature in buildings. Upper-room UV effectively combats various viruses and bacteria, including those that pose bioterrorism threats. The technology is extensively researched and developed, demonstrating its effectiveness across diverse environments. It offers versatility, making it suitable for retrofitting in various building types, including hospitals, healthcare clinics, urgent care centers, childcare facilities, colleges, prisons, and virtually all building categories. Its cost-effectiveness makes it a compelling choice compared to alternatives like dilution and filtration. These facts underscore the value of implementing upper-room UV-C for infectious diseases, including common colds, the flu, and other contagious agents.
The effectiveness of upper-room UVGI varies based on the type of ventilation system employed. Proper design is essential to ensure optimal air circulation and to promote air mixing while maintaining indoor comfort conditions. In technical terms, UVGI should target comprehensive air disinfection.
Another critical parameter is the UVGI dose delivered to microorganisms, dependent on UV irradiance and exposure time. The key distinction between surface and air disinfection lies in exposure time. Given the rapid movement of air within enclosed spaces, UVGI requires sufficiently high irradiance levels to deliver the required UVGI dose.
Additional factors include room configuration, UVGI fixture placement, and the adequacy of airflow for transporting contaminated air to the upper room.
Alfaa UV, a company with more than 2 decades of experience in UV technology, offers UVGI solutions for surfaces, upper air, and HVAC applications. In the present times, UVGI solutions offered by Alfaa UV have been used to mitigate the risk of rapid infections within closed spaces. Here we talk about the STERO-UP Upper-Air UVGI solution which has a wide impact and applicability.
Alfaa UV’s new range of disinfecting appliances, STERO-UP Upper-Air UVGI Systems, involve exceptionally potent germicidal UV irradiation, having extensive coverage of the upper sections of any given room. The advanced engineered upper air purification systems can be installed just like an air conditioner, at a safe height, and aids in superior infection control using powerful UVC irradiation.
Incorporating Alfaa UV’s STERO-UP Upper-Air UVGI System into indoor environments significantly contributes to improved air quality and enhanced infection control.
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