COVID-19, which started in 2020, is thought to spread mainly through respiratory droplets and close contact from person to person. Wearing a mask can prevent a person from being exposed to the COVID-19 virus and is considered to be the most convenient tool. Wearing a mask is now part of daily lives for the public. In the beginning of the COVID-19 pandemic, the government placed a control on the distribution of masks to the public due to the supply shortage. Now, the control has been eased and the mask supply is stabilized. However, another issue related to masks has surged recently, which some masks appear to have some peculiar odor. This peculiar oder makes users uncomfortable. To discover what caused this peculiar odor, we tested masks available in the market from different manufacturers.