Air Cleaning for Covid-19

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Recently, a systematic modelling study published in the journal Physics of Fluids shows that improved ventilation can lower the risk of transmission of the Covid-19 virus.

About the Experiment

• The scientists measured the clean air delivery rate of the air cleaning system.
  • Tobacco smoke was used to simulate the airborne virus.
• The experimental measurements were incorporated into a detailed computational model of a classroom, which mostly lacks adequate ventilation systems and a possible hotspot for infections in the children.
• A low-cost air cleaner can be easily constructed from a cardboard frame, topped by an air filter and a box fan.
  • The air filter is placed between the fan and the cardboard base. The fan is oriented so that air is drawn in from the top and forced through the filter, discharging cleaned air downward.
• In addition to the box fan air cleaner, a ventilation unit known as a Horizontal Unit Ventilator (HUV) was included in the simulation.
• A cloud of virus particles was assumed to enter the simulation from an infected individual, presumably the class teacher and experimented with different placements of the air cleaner.
• Findings and Significance
  • The simulations showed the best results were obtained by shifting both the box fan air cleaner and the infected teacher to a location near the HUV.
  • At this location, owing to its proximity to both the infector and the HUV, the air cleaner extracts the majority of aerosols, leaving only a small percentage suspended in the air.
  • These inexpensive units can greatly decrease the amount of airborne virus in these spaces if used appropriately.
• Recommendations
  • Although placing the air cleaner near an infected individual is best, it is not always possible to know who is infected.

• In this situation, the investigators recommend placing the air cleaner near the HUV.
• In large classrooms, distributing multiple air cleaners in the space is more effective in controlling aerosol spread than simply enhancing the flow rate of the HUV or air cleaners alone.

(Image Courtesy: AIP)

(Image courtesy: EA)

Source: IE