Transmission Risk

The purpose of this project is to quantify the effects that HVAC vent placement have on infection transmission risk. To accomplish this, a parametric room design was created where the only changes between room configurations is the location of the vents. A novel method of quantifying exposure risk was developed to illustrate the risk of exposure from one occupant to another.

The velocity results of all simulations are shown at left. They are grouped into the 180 simulations and 90 simulations for ease of comparison. The velocity results show significant differences between each case, allowing for the possibility of infection transmission risk comparison between cases. Streamlines were calculated for each case and indicate the presence of recirculation zones which, intuitively, are likely to increase infection transmission risk to the occupants.

The gif on the left may take some time to load.

This animation shows how particles released from the shown individual might propagate in a room during one hour. The simulation techniques for these particles were written in Python. This result is from an individual releasing particles into the 180-U-L room configuration. As evident from the animation, respiratory droplets can be transported throughout the entire room, potentially infecting individuals throughout the space.

To quantify this risk of exposure, we can mathematically place individuals throughout the room and use the quantification method described in the last image.

A total of 11 exposed subjects were used for an exposure analysis from one infected individual. The figure shown at right indicated the location of subjects for each room configuration when Subject 0 is the infected individual (shown in red). The subjects shown in yellow were iteratively chosen as the infected individual and these simulations were performed separately. The subjects shown in orange are placed near the infected subject and their relative position to the infected subject is always the same, e.g. Subject 5 is always 0.5 m away from the infected subject in the +x direction.

The 11 exposure calculations per each of the 120 Room Configuration/Infected Subject/Particle Model set gives us a total of 1,320 data points. The exposure risk for each of the 11 individuals can be calculated at the same time using one of the 120 sets described earlier.

Shown here are the 1,320 calculated exposure indices on a log-y scale as a function of the distance between the infected subject (patient) and the exposed subject in meters. From these results, it appears that the six feet social distancing guidelines are not enough to guarantee zero exposure risk in indoor spaces. This means that masks should still be worn indoors as their effectiveness at reducing infection transmission risk is well documented.

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