Updated: May 14, 2021 7:32:33 am
Improved ventilation can lower the risk of transmission of the Covid-19 virus, but many school classrooms lack adequate ventilation systems. Scientists have proposed using a simple air cleaner with a box fan. In a systematic modelling study in the journal Physics of Fluids, published by the American Institute of Physics, they have shown that these inexpensive units can greatly decrease the amount of airborne virus in these spaces, if used appropriately.
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.
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In experiments at two independent laboratories, 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. In addition to the box fan air cleaner, a ventilation unit known as an HUV (horizontal unit ventilator) was included in the simulation.
A cloud of virus particles was assumed to enter the simulation from an infected individual. The scientists assumed this individual was the class teacher and experimented with different placements of the air cleaner.
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. 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.
—Source: American Institute of Physics
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