Airborne transmission of COVID-19 and mitigation using box fan air cleaners in a poorly ventilated classroom

Ruichen He; Wanjiao Liu; John Elson; Rainer Vogt; Clay Maranville; Jiarong Hong

doi:10.1063/5.0050058

Airborne Transmission of COVID-19 and Mitigation Using Box Fan Air Cleaners in a Poorly Ventilated Classroom

10.1101/2021.03.11.21253395 ◽

2021 ◽

Author(s):

Ruichen He ◽

Wanjiao Liu ◽

John Elson ◽

Rainer Vogt ◽

Clay Maranville ◽

...

Keyword(s):

Risk Mitigation ◽

Low Cost ◽

Substantial Reduction ◽

Systematic Investigation ◽

Transmission Risk ◽

Thermal Plume ◽

Airborne Transmission ◽

Resource Limited ◽

Air Cleaner ◽

Air Cleaners

ABSTRACTMany indoor places, including aged classrooms and offices, prisons, homeless shelters, etc., are poorly ventilated but resource-limited to afford expensive ventilation upgrade or commercial air purification systems, raising concerns on the safety of opening activities in these places in the era of COVID-19 pandemic. To address this challenge, using computational fluid dynamics, we conducted a systematic investigation of airborne transmission in a classroom equipped with a single horizontal unit ventilator (HUV) and evaluate the performance of low-cost box fan air cleaner for risk mitigation. Our study shows that placing box fan air cleaners in the classroom results in a substantial reduction of airborne transmission risk across the entire space. The air cleaner can achieve optimal performance when placed near the asymptomatic patient. However, without knowing the location of the patient, the performance of the cleaner is optimal near the HUV with the air flowing downwards. In addition, we find that it is more efficient in reducing aerosol concentration and spread in the classroom by adding air cleaners in comparison with raising the flow rate of HUV alone. The number and placement of air cleaners need to be adjusted to maintain its efficacy for larger classrooms and to account for the thermal gradient associated with human thermal plume and hot ventilation air during cold seasons. Overall, our study shows that box fan air cleaners can serve as an effective low-cost alternative for mitigating airborne transmission risks in poorly ventilated spaces.

Download Full-text

Don't purchase high ozone air cleaners

PsycEXTRA Dataset ◽

10.1037/e456172008-008 ◽

2008 ◽

Keyword(s):

Air Cleaners

Download Full-text

385. Performance Comparison of Indoor Air Cleaners

10.3320/1.2758422 ◽

2004 ◽

Author(s):

C. Chen ◽

K. Chang ◽

T. Lin ◽

C. Hsu ◽

Y. Lee ◽

...

Keyword(s):

Indoor Air ◽

Performance Comparison ◽

Air Cleaners

Download Full-text

Peering inside a cough or sneeze to explain enhanced airborne transmission under dry weather

Scientific Reports ◽

10.1038/s41598-021-89078-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Kai Liu ◽

Majid Allahyari ◽

Jorge S. Salinas ◽

Nadim Zgheib ◽

S. Balachandar

Keyword(s):

High Fidelity ◽

Substantial Variation ◽

Ambient Conditions ◽

Airborne Transmission ◽

Social Distancing ◽

Virtual Experiments ◽

Long Time ◽

Simulation Results ◽

High Fidelity Simulations ◽

Droplet Nuclei

AbstractHigh-fidelity simulations of coughs and sneezes that serve as virtual experiments are presented, and they offer an unprecedented opportunity to peer into the chaotic evolution of the resulting airborne droplet clouds. While larger droplets quickly fall-out of the cloud, smaller droplets evaporate rapidly. The non-volatiles remain airborne as droplet nuclei for a long time to be transported over long distances. The substantial variation observed between the different realizations has important social distancing implications, since probabilistic outlier-events do occur and may need to be taken into account when assessing the risk of contagion. Contrary to common expectations, we observe dry ambient conditions to increase by more than four times the number of airborne potentially virus-laden nuclei, as a result of reduced droplet fall-out through rapid evaporation. The simulation results are used to validate and calibrate a comprehensive multiphase theory, which is then used to predict the spread of airborne nuclei under a wide variety of ambient conditions.

Download Full-text

Australia must act to prevent airborne transmission of SARS‐CoV‐2

The Medical Journal of Australia ◽

10.5694/mja2.51131 ◽

2021 ◽

Author(s):

Zoë Hyde ◽

David Berger ◽

Andrew Miller

Keyword(s):

Airborne Transmission

Download Full-text

Air circulation in a gastrointestinal light source box and endoscope in the era of SARS-CoV-2 and airborne transmission of microorganisms

Endoscopy International Open ◽

10.1055/a-1336-3280 ◽

2021 ◽

Vol 09 (03) ◽

pp. E482-E486

Author(s):

Stanislas Chaussade ◽

Einas Abou Ali ◽

Rachel Hallit ◽

Arthur Belle ◽

Maximilien Barret ◽

...

Keyword(s):

Light Source ◽

Cooling System ◽

Air Cooling ◽

Airborne Transmission ◽

Plastic Tube ◽

Care Workers ◽

Air Cooling System ◽

Forced Air ◽

Air Circulation ◽

Closed Environment

Abstract Background and study aims The role that air circulation through a gastrointestinal endoscopy system plays in airborne transmission of microorganisms has never been investigated. The aim of this study was to explore the potential risk of transmission and potential improvements in the system. Methods We investigated and described air circulation into gastrointestinal endoscopes from Fujifilm, Olympus, and Pentax. Results The light source box contains a lamp, either Xenon or LED. The temperature of the light is high and is regulated by a forced-air cooling system to maintain a stable temperature in the middle of the box. The air used by the forced-air cooling system is sucked from the closed environment of the patient through an aeration port, located close to the light source and evacuated out of the box by one or two ventilators. No filter exists to avoid dispersion of particles outside the processor box. The light source box also contains an insufflation air pump. The air is sucked from the light source box through one or two holes in the air pump and pushed from the air pump into the air pipe of the endoscope through a plastic tube. Because the air pump does not have a dedicated HEPA filter, transmission of microorganisms cannot be excluded. Conclusions Changes are necessary to prevent airborne transmission. Exclusive use of an external CO2 pump and wrapping the endoscope platform with a plastic film will limit scatter of microorganisms. In the era of pandemic virus with airborne transmission, improvements in gastrointestinal ventilation systems are necessary to avoid contamination of patients and health care workers.

Download Full-text