Evaluation of UR-UVGI System for Sterilization Effect on Microorganism Contamination in Negative Pressure Isolation Ward

Abstract

A negative pressure isolation ward prevents the outflow of airborne microorganisms from inside the ward, minimizing the spread of airborne contamination causing respiratory infection. In response to recent outbreaks of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), Korea has increased the number of these facilities. However, airborne contaminants that flow into the ward from adjacent areas may cause secondary harm to patients. In this study, the sterilization effect of upper-room ultraviolet germicidal irradiation (UR-UVGI) on microorganisms generated within the negative pressure isolation ward and those flowing inward from adjacent areas was evaluated through field experiments and computational fluid dynamics (CFD) analysis, to assess the potential of this approach as a supplementary measure to control such microorganisms. The sterilization effect was found to be not high because of high-level ventilation. CFD analysis under various conditions shows that the sterilization effect for indoor-generated microorganisms varies with the level of UV radiation, the source locations of the indoor-generated microorganisms, air supplies and exhausts, the UVGI system, and the airflow formed under the specified conditions. Our results show that when the UVGI system is installed in the upper part of the ward entrance, contaminated air from adjacent area is strongly sterilized.

Airborne and aerosol pathogen transmission modeling of respiratory events in buildings: An overview of computational fluid dynamics

“…COVID-19 transport in enclosed spaces has been studied in different types of buildings such as hospitals ( Yu et al, 2017 , Qian and Zheng, 2018 , Verma et al, 2017 , Yam et al, 2011 , Anghel et al, 2020 , Sahu et al, 2019 , Leung et al, 2005 , Chow et al, 2006 , Bang et al, 2018 , Zhu et al, 2012 ), public transportation ( Zhang and Li, 2012 , Han et al, 2014 , Farag and Khalil, 2015 ), schools ( Coleman and Sigler, 2020 , Feng et al, 2012 ), offices ( He et al, 2011 , Azimi and Stephens, 2013 ), and residential buildings ( Gao et al, 2009 , Li et al, 2005 ). Reviewing the literature reveals that the background airflow pattern is a pivotal factor in airborne disease transmission, which is highly affected by different parameters related to (1) space (e.g., geometry and layout, usage type, equipment and furniture, and infiltration rate from cracks and voids), (2) HVAC (e.g., type of ventilation system, supply air parameters), (3) occupant (e.g., respiration performance, activity type such as walking, sitting or other types of activities ( Morawska, 2005 , Zhang et al, 2019 ).…”

“… # Item [unit] Interval Reference 1 Droplet size distribution [µm] 0.5 – 2000 + ( Table 8 , Table 9 ) ( Aliabadi et al, 2010 , Lindsley et al, 2013 , Wei and Li, 2017 , Day et al, 2010 , Sokoray-Varga and Józsa, 2008 , Janke et al, 2019 , Bahl et al, 2020 , Chao et al, 2009 ) 2 Number of droplets/particles 5000, 9 × 10 6 ( Aliabadi et al, 2010 , Stabile et al, 2015 ) 3 Indoor/outdoor space Different Boundary Condition. ( Khosronejad et al, 2020 ) 4 Local ambient air velocity[m/s] [0.25-1.5], 21.7, 0- 10 ( Zhang et al, 2019 , Stabile et al, 2015 ) 5 Local ambient air direction [deg] 0 -180 ( Buonanno et al, 2009 ) 6 Local ambient air humidity [%] ( Leung et al, 2005 – ( Mead-Hunter et al, 2013 ), 50 ( Aliabadi et al, 2010 ), ( Zhang et al, 2019 ) 7 Local air temperature [°C] ( Yam et al, 2011 , Anghel et al, 2020 , Sahu et al, 2019 , Leung et al, 2005 , Chow et al, 2006 , Bang et al, 2018 , Zhu et al, 2012 ), 25, ( Zhang et al, 2019 ), ( Stabile et al, 2015 ) 8 Temporal profile o...…”

The Wavelength-Based Inactivation Effects of a Light-Emitting Diode Module on Indoor Microorganisms

“…Sung et al [ 4 ] tested the sterilization effect of UR-UVGI in a room in the general ward of a hospital, analyzing the sterilization effect based on the ventilation efficiency using computational fluid dynamics (CFD). Bang et al [ 5 ] experimentally verified the sterilization effect of UR-UVGI in a negative pressure isolation ward—a facility to isolate infected patients—and compared the sterilization effects based on the installation location using CFD. In-duct (ID)-UVGI, which is installed and used inside an air handling unit (AHU), is easy to use because people are not directly exposed to it.…”

Viruses such as SARS-CoV-2 can be partially shielded from UV radiation when in particles generated by sneezing or coughing: Numerical simulations

“…Solar UV radiation near the Earth's surface, primarily UVB at 280-315 nm, can inactivate SARS-CoV-2 [ 58 , 67 ] and other microbes [61] . UVC (200-280 nm) is common for germicidal applications [ 4 , 14 , 16 , 32 , 35 , 59 , 76 ].…”