Effectiveness of upper-room UVGI system in a classroom with mixing and displacement ventilation

This study investigates the effectiveness of an upper-room UVGI system in a small classroom. Mixing ventilation can increase virus removal when combined with a UVGI system more effectively than displacement ventilation combined with a UVGI system, especially in cases where the ventilation rate is low. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

CFD Modeling of Room Air Flow Effects on Inactivation of Aerosol SARS-CoV-2 by an Upper Room Ultraviolet Germicidal Irradiation (UVGI) System

Ultraviolet germicidal irradiation (UVGI) inactivates viral aerosols in indoor environments. Upper room UVGI systems use wall or ceiling mounted fixtures to create a disinfection zone above the occupied zone. The performance of upper room UVGI systems varies with indoor airflow induced by mechanical ventilation and thermal plumes from occupants, which carries contaminated air into the disinfection zone where viral aerosols are partially inactivated before circulating back into the breathing zone. This study used computational fluid dynamics (CFD) modeling to investigate the effect of an upper room UVGI system on spatial distributions of viral aerosols with UV-C susceptibility representative of coronaviruses as a function of ventilation system characteristics. Upper-room UVGI confined elevated viral aerosol concentrations to the vicinity of an infector, while the room average viral aerosol concentration was reduced by two orders of magnitude relative to a case without UVGI. Return air recirculation rates and ventilation strategy (i.e. mixing vs. displacement) had notable effects on the disinfection effectiveness of the UVGI system. For mixing ventilation, as the recirculation air flow rate increased from 0 to 5.3 h(-1) with a fixed outdoor air flow of 0.7 h(-1), UVGI inactivation escalated by 62%. Mixing ventilation at 0.7 h(-1) without recirculation in the room with a volume of 108 m(3) was 30% more effective in inactivating airborne viruses than displacement ventilation, due to the higher air mixing.

Does the Covid-19 Pandemic Have an Impact on the Care of Acute Appendicitis (Aa) in Children?

BACKGROUND AND AIM: The coronavirus disease 2019 (COVID-19) has deepened the existing health inequalities and has limited access to health services. The aim of this study was to assess the impact of the COVID-19 pandemic on the care of AA in children at a single institution in Sfax, Tunisia. METHOD(S): We divided our patients into two groups: the first (COVID group) included patients who had surgery during covid-19 pandemic (between March 02, 2020, and December 31, 2020), while the second (pre-COVID group) included those who had appendectomy before the pandemic (between March 02, 2019, and December 31, 2019). RESULT(S): A total of 275 patients were included. The COVID-19 group included 136 patients and the pre- COVID-19 group 139 patients. Multivariate logistic analyses revealed that time from onset of abdominal pain to arrival to the emergency department was higher in COVID group patients (36 [24-48] hours vs 30 [12-48] hours, p-value = 0.023). Patients undergoing surgery during the COVID era had a significantly higher Alvarado score (7 [5-8] vs 6 [5-7], p value = 0.002). We have found no differences between the two study groups with respect to outcomes including length of hospital stay, re-admission rate, re-operation rate, and postoperative complications rate. CONCLUSION(S): this is the first study, in Tunisia, to assess the impact covid-19 pandemic on the care of AA in children. We suggest that strategies should be implemented to educate parents and to encourage them to seek for an emergent care of potentially serious conditions such as AA.

Effects of Indoor Airflow and Ventilation Strategy on the Airborne Virus Transmission

Recent worldwide outbreaks of coronavirus disease (COVID-19) have threatened global public health. A few new studies indicated a strong possibility of airborne transmission of the virus through aerosols (airborne particles smaller than 5 mu m in diameter). Indoor airflow and environmental conditions can play critical roles in aerosol transport and airborne disease transmission. This study investigates the impacts of ventilation strategy (mixing and displacement) and ventilation rate on the virus aerosol distribution and human exposure, considering the aerosol emission mode (talking and breathing) and personal physical distance. The study results show that under displacement ventilation with a minimum ventilation rate, the exhalation jet from infector can penetrate into the breathing zone of the exposed person, resulting in a higher human exposure to viral aerosols than mixing ventilation case. Increasing the ventilation rate can effectively reduce the human exposure due to a dilution effect and a more pronounced air stratification. The results reveal that the aerosol emission mode determines the initial aerosol trajectories from the infector. The exhaled aerosols from talking can reach the breathing zone of another person even at 2 m [6.6 ft] distance.