Designed for people’s health, breathing valve masks filter visible and invisible substances in the air that are harmful to the human body so that they do not adversely affect the body. It is important to note that masks with breathing valves filter the air that is inhaled, but not the air that is exhaled. Therefore, for the general population, masks with breathing valves can be worn to protect the wearer. For patients with new cases of pneumonia, suspected infected persons and close contacts during the incubation period, masks with respiratory valves should not be worn because the respiratory valves do not block the droplets from the wearer from spreading to the environment, which may result in the spread of the virus. Source: Dr. Yurai