Matthew Stamats is testing different masks. Source: NIST
Many people wear masks in public to slow the spread of COVID-19, following the recommendations of the Centers for Disease Control and Prevention. However, masks with exhalation valves do not slow the spread of infection. New videos from the US National Institute of Standards and Technology (NIST) demonstrate why.
The video shows airflow through masks with and without exhalation valves. Materials were created by NIST Research Engineer Matthew Stamats. Videos posted along with a companion research paper in Physics of Fluids…
“When you compare videos side-by-side, the difference is striking,” said Staymats. “These videos show how the valves allow air to escape from the mask without filtering it, which goes against the very essence of the mask.”
The exhalation valves make breathing through the mask easier and more comfortable. They are appropriate when the mask is intended to protect the user himself. For example, masks with valves protect workers from dust on a construction site or hospital staff from infected patients.
The masks that are recommended to slow the spread of COVID-19 are primarily designed to protect people around the wearer. They trap exhaled droplets that may contain the virus, and thus slow the spread of the infection. According to experts, even people without symptoms should wear masks because they can carry the disease asymptomatically.