The protracted coronavirus disease (COVID-19) pandemic has caused an unprecedented global health, social, economic, and psychological crisis. COVID-19 is transmitted via droplets, which include volatile organic compounds (VOCs) emitted by COVID-19 carriers. As a result, medical healthcare workers interacting with COVID-19 patients are at a high risk of infection. In this study, we measured the concentration of total VOCs (TVOCs) in the droplets of patients during conversations.


Thirty patients aged 20–88 years were enrolled in this study. The amounts of VOCs, formaldehyde (HCHO), and carbon dioxide (CO2) as surrogate parameters for the patient’s droplets were measured at a distance of 1 m from the patients under the following conditions: 1) no conversation with a mask on, 2) conversation with a mask on, 3) conversation without a mask on, and 4) no conversation without a mask on.


The average concentrations of TVOCs (mg/m3), HCHO (mg/m3), and CO2 (ppm) were all the lowest before the masked conversation (1.79 ± 1.72, 0.25 ± 0.25, 1193 ± 516), increased during the masked conversation (1.99 ± 1.87, 0.29 ± 0.24, 1288 ± 555), were the highest during the unmasked conversation (3.10 ± 1.86, 0.45 ± 0.28, 1705 ± 729), and decreased to baseline after the unmasked conversation (1.89 ± 1.88, 0.26 ± 0.27, 1191 ± 518, respectively). Variations in TVOC and HCHO concentrations were positively correlated with patient age (TVOC: r = 0.42, p = 0.019 and HCHO: r = 0.47, p = 0.008).


Wearing a mask reduced the VOC concentrations measured during conversations more than when a mask was not worn. Therefore, wearing a mask can reduce the emission of airborne droplet-derived VOCs and thereby reduce the risk of transmission of unknown patient-derived infections.

Clinical Trial Registration no:

The Clinical Trial Registration no: (UMIN000039595)

Keywords: Airborne droplets, Conversation, Mask, Carbon dioxide, Formaldehyde, Volatile organic compounds.
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