In the second installment of our Design Thinking series, we look at how UVGI technology can be used to inactivate microorganisms and mitigate the exposure of COVID-19 in commercial buildings.

Infection control practices have become a key topic of discussion as we question whether highly populated spaces are safe to inhabit. Air purification technology, once primarily a concern of the healthcare industry, must now be applied to restaurants, grocery stores, retail, workplace, and education spaces.

We are using our deep knowledge of these buildings and spaces to study how this proven technology can be applied to make our clients’ projects safer. After all, investing in an appropriate long-term solution for your use is pivotal.

In this article we will look at UVGI. But first, it’s important to clarify what COVID-19 is and how it spreads.

SARS-CoV-2 is the classification of the novel coronavirus that causes COVID-19, which has turned into a worldwide pandemic. The coronavirus is believed to be transmitted person-to-person primarily through respiratory droplets. These respiratory droplets become entrained aerosols from infected persons and can spread particularly well in enclosed indoor environments.

Ultraviolet radiation has been identified as an existing technology that has a high likelihood of inactivating the SARS-CoV-2 novel coronavirus. The entire ultraviolet spectrum is capable of inactivating microorganisms, but UV-C radiation (within the range of 100–280 nm), is considered most effective with 265 nm considered the optimum wavelength. UV-C radiation works by damaging the DNA and RNA of microorganisms (including viruses, bacteria, and fungi) and rendering them unable to replicate.  

Image courtesy of ASHRAE Learning Institute

While scientific testing results of ultraviolet radiation treatment on SARS-CoV-2 does not exist at this time, experts believe the effectiveness is likely high, based on UV-C efficacy on related airborne viruses such as SARS and MERS. Current UV-C technology for germicidal applications in HVAC typically employs low-pressure mercury lamps. LED lamps for germicidal use are in the early stages of development but are not yet considered viable options.

UV-C lamps for germicidal irradiation (abbreviated UVGI), have traditionally been deployed on HVAC cooling coils to prevent mold growth on wet coil surfaces. These systems were typically designed to deactivate 85% of microorganisms in a single pass. However, with the SARS-CoV-2 virus, attention has now been focused on applications that can handle higher deactivation rates.  With a higher concentration of UVGI lamps, systems can be designed to a deactivation rate of 99.98% in a single pass. These UVGI systems are often referred to as “on-the-fly” deactivation systems since the majority of microorganisms are deactivated in a single pass. On-the-fly deactivation systems are generally designed for full duct coverage of an airstream with lamps installed 4" on center and having an overall lamp input power above 30 W/ft2 of duct cross-sectional area.

Image of coil disinfection installation, courtesy of ASHRAE Learning Institute

Image of 99.98% deactivation (on-the-fly) installation, courtesy of ASHRAE Learning Institute

We expect to see more commercial buildings making use of UVGI technology in both new and existing HVAC systems. While complete threat removal of airborne contagion is not possible in spaces containing infected occupants, exposure risk can be mitigated to the greatest extent possible using proven technologies.  

Sources:

ASHRAE COVID-19 Resources webpage

Reducing Infectious Disease Transmission with UVGI, ASHRAE Learning Institute, Presenter:  William P. Bahnfleth, 2020

Illuminating Engineering Society COVID-19 Resources webpage

Has your business started researching methods for eliminating COVID-19 contamination in your buildings? We would love to share our knowledge with you.

Contact Scott West, P.E., today to learn more about how we can help you!