Many people wear masks in public to slow the spread of COVID-19, as recommended by the Centers for Disease Control and Prevention (CDC). However, masks with exhalation valves do not slow the spread of the disease, and now, new videos from the National Institute of Standards and Technology (NIST) show why.

Why shouldn't material masks with exhalation valves be used during the COVID-19 pandemic?

• Do NOT wear cloth masks with exhalation valves or vents since they allow respiratory droplets containing the virus to escape.

Can I wear masks with exhalations valves during COVID-19?

Masks with vents or exhalation valves are not advised because they allow unfiltered breath to escape the mask.