The Centers for Disease Control and Prevention has updated its mask guidelines during the pandemic, advising against wearing masks that have vents or valves.

The CDC says the purpose of masks is to keep respiratory droplets from reaching others, and masks with one-way valves or vents allow exhaled air to be expelled out through holes in the material. This can allow droplets to reach others and potentially spread the COVID-19 virus.

Instead, masks should be made of tightly woven material.

Masks with exhalation valves are not permitted at Moffitt Cancer Center. For patients and visitors, a surgical mask may be worn over an exhalation valve mask or the exhalation valve mask can be replaced with a disposable mask.

The reduce the spread of COVID-19, the CDC recommends that people wear masks in public settings when around people outside of their household, especially when other social distancing measures are difficult to maintain.