A Study of Expiratory Droplet Dispersion and Deposition Density in an Enclosed Residential Space

This study attempts to compare the density of human expiratory droplet deposition on commonly exposed/used surfaces of an indoor residential setting by simulating the droplet exhalation using mist sprays filled with a colored medium. The simulation is not an exact replica of a human exhale but is designed to reveal the variations between surfaces. The droplets dispersed in expiratory air in an indoor environment can carry microorganisms, both bacteria and viruses, causing respiratory infections. The process involved a human actor performing predefined daily tasks and was followed around by a second actor, who mimicked breath exhalation using mist sprays. The activities included reading a magazine, watching TV, using a mobile phone, a laptop, making tea, receiving visitors, and talking to a friend. Paper surfaces were used to collect the spray pigment. The results were scanned and analyzed by a computer. The output was in the form of percentage and pixel count of colored pigment on each paper. The results showed that the most significant percentage of pigment was received on the surfaces that simulated activities performed closest to the face. The top recipient of pigment by far was the mobile phone, followed by the remote controller, laptop, keyboard, and mouse. The surfaces farthest from the face, such as the floor, received little to no detectable pigment.

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