Masks with a 'breathable valve' are less effective and could let viral particles through, according to experts

Face masks have increasingly become a fact of public life in countries battling the novel coronavirus. 

As people wrestle with the inconvenience and discomfort of wearing masks, some entrepreneurs are stepping in to offer a masks with so-called "breathable valves" that contain a special opening to regulate the flow of air.

According to ads for these masks, which are popping up on marketplaces like Amazon, social media, and news sites, the valve allows for a more comfortable mask that's easy to breath in. But medical experts say the valves make the masks almost useless when it comes to the coronavirus. 

Surgeon, writer, and public health researcher Dr. Atul Gawande called attention to the masks on Twitter, where he said they had appeared in his targeted ads, and were "evil" and "need to be banned."

There's still a lot that even experts don't know when it comes to masks, including how well different types actually work against viral particles. 

But valved masks could be especially risky since they offer a false sense of protection, according to Dr. Ashvind Bawa, a surgeon and associate professor at Dayanand Medical College & Hospital. 

Bawa posted a YouTube video earlier in May that demonstrates a problem with the valved masks. The valve works by opening when the user breathes out, allowing better airflow. But that also means it allows particles to pass through, including respiratory droplets that potentially contain viral contagions.

"It is open to everything and the virus can easily spread out," Bawa said in the video. 

These types of masks (and any masks with a valve) can stop environmental pollutants from coming into the mask, which is what they're designed to do, he said, but aren't safe for preventing viral spread. 

That's because masks prevent the spread of the virus in two ways: protecting the mask-wearer from outside particles contacting their nose or mouth and spreading disease, and protecting the people around the mask-wearer by containing any viral particles they might be expelling.

But a valved mask, as Bawa explains in the video, doesn't offer protection in both directions, and so could offer a false sense of security to people wearing them, which has been the concern of some medical professionals about face masks in general. 

The CDC also says that valved masks offer protection for the wearer, but can release particles into the surrounding area, which is why they're not recommended in healthcare settings.

"Respirators with exhalation valves should not be used in situations where a sterile field must be maintained (e.g., during an invasive procedure in an operating or procedure room) because the exhalation valve allows unfiltered exhaled air to escape into the sterile field," according to the CDC website.

For medical workers, who are at high risk of infection while working with patients and with each other, it's crucial to take every precaution against wayward particles, since one infection could quickly spread across a healthcare facility. 

This is especially true for a pathogen like the novel coronavirus because research has found many people can be contagious even if they don't have symptoms. 

As such, some experts have emphasized that masks are most protective if everyone wears them, and wears them correctly. 

Read more:

'Anti-maskers' say they should not be forced to cover their faces in public because medical conditions mean they cannot wear a mask

We asked 15 public health experts if homemade masks are a good idea to limit the spread of the coronavirus, and the results are mixed

All the different types of face masks, and who should wear them during the coronavirus pandemic