Why do some masks have valves and why are they being banned?

With mask requirements now commonplace around the world as the fight against coronavirus continues, experts have warned that not all facial coverings protect both the wearer and those around them from the virus.

Some types of masks, including N95 masks as well as cloth masks, include a plastic one-way valve on the front that makes it easier to breathe.

When you breathe in, the valve is closed, but when you breathe out, it opens to allow your exhalation to leave unfiltered.

Why are face masks with valves not recommended for protection against the coronavirus?

According to the Mayo Clinic, these types of masks do not protect others from coronavirus, as the one-way valve which allows unfiltered air to be released when the wearer exhales means the wearer can spread the virus as easily as not wearing a mask.

“It defeats the purpose,” Kai Singbartl, a medical doctor who is the chair for infection prevention and control at the Mayo Clinic in Arizona, told USAToday. “They are unfiltered, those valves are the path of least resistance so to speak, it’s easier to exhale and get rid of the heat and moisture.”

In addition to getting rid of heat and moisture, the valves also allow wearers to exhale “viral droplets and particles,” Dr Singbartl said.

According to the CDC, coronavirus is thought to spread “mainly from person to person, mainly through respiratory droplets produced when an infected person coughs or sneezes.”

Considering those who have coronavirus but are asymptomatic can still spread the virus, it is important to wear a mask that protects both the wearer and others.

“The purpose of masks is to keep respiratory droplets from reaching others to aid with source control,” the CDC reiterates on its website. “Masks with one-way valves or vents allow exhaled air to be expelled out through holes in the material. This can allow exhaled respiratory droplets to reach others and potentially spread the Covid-19 virus.

“Therefore, CDC does not recommend using masks or if they have an exhalation valve or vent.”