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

CDC ‘does not recommend using masks if they have an exhalation valve or vent’

Chelsea Ritschel
Tuesday 06 October 2020 15:08 BST
Related video: Coronavirus: How effective are homemade face masks?
Related video: Coronavirus: How effective are homemade face masks?

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.

Recently, multiple airlines have amended their mask policies to prohibit face coverings with valves.

“Any mask with an exhaust valve is not approved as an acceptable face mask for customers travelling on any Delta operated flight,” the airline announced in August, with United Airlines and JetBlue sharing similar announcements.

Alaska Airlines also updated its mask policy, listing “face coverings with direct exhaust valves” under its “unacceptable face coverings” section.

In April, San Francisco and multiple other counties in California announced that face masks with valves do not comply with the law requiring individuals to wear masks, an amendment also expressed in Denver, Colorado.

The increasingly common ban on masks with valves comes as researchers have learned more about how the coronavirus spreads, and the risk that the valves pose.

This is what you need to know about face masks with valves.

What is a face mask with a valve and what does the valve do?

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.

According to Fast Company, masks with valves were originally created for industrial work so that workers could breathe easier in factories where facial coverings were necessary.

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.”

Do medical professionals wear masks with valves?

The CDC recommends that hospitals do not use N95s with valves.

“Respirators with exhalation valves should not be used in situations where a sterile field must be maintained (eg, during an invasive procedure in an operating or procedure room) because the exhalation valve allows unfiltered exhaled air to escape into the sterile field,” the health organisation explains.

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