Aerosol transmission of neocoronavirus through floor drains from sewers has not been reported, but previous cases of aerosol transmission through sewers exist for SARS and Middle East respiratory syndrome, which are both coronavirus infections. Whether the new coronavirus can be transmitted through aerosols is yet to be clarified, and if the new coronavirus can be transmitted through aerosols, it also needs to reach an effective concentration to cause disease. The effectiveness of transmission is significantly reduced with proper ventilation, liquid containment of sewers, and other operations. It is important to check the building’s drainage and ventilation system for defects, such as whether there is enough water in the U-shaped pipes of flush toilets and the water seal of floor drains, and whether air from the patio flows back into the room through the exhaust fans.