As novel coronavirus cases rise each day, public health experts and doctors repeatedly convey a message: wearing masks saves lives.

Robert R. Redfield, director of the Centers for Disease Control and Prevention, said in July that cloth face coverings are one of the most effective weapons that can slow down and stop the spread of the virus- especially when used universally in a community setting.

A group of researchers from Duke University questioned the efficacy of the various face coverings. The research unveiled a simple method to study the effectiveness of various types of masks by analyzing more than a dozen different facial coverings like hospital grade N95 respirators, bandanas and more.

Out of 14 masks and various coverings that were tested, the study revealed that some easily accessible cotton cloth masks are as effective as surgical masks. But neck gaiters made of stretchy and thin material could be worse than not wearing a mask.

The search for a way to probe the effectiveness of different masks was initiated by a request from a professor at Duke’s medical school working to provide at-risk and underserved populations in Durham, N.C., with face coverings.

With the option of so many varieties of masks each claiming to block the virus, the professor reached out for help in the university’s physics department from Martin Fischer, a chemist and physicist.

A simple contraption is used that harnesses the power of a laser that can be purchased online for less than $200 and a cell phone camera. Fischer created a device allowing his team to track individual particles that get released from a person’s mouth as they speak.

The remaining setup includes a box made out of cardboard and a lens.

The commonly used N95 mask at hospitals, was found to be most effective, said one of the study’s co-author, Warren S. Warren, a professor of physics, chemistry, radiology and biomedical engineering at Duke. He noted that the mask allowed “no droplets at all” to come out.

Infact, a breathable neck gaiter, ranked worse than the no-mask control group. The gaiter used by researchers to test was described as “neck fleece” made from a polyester spandex material, said Warren.

Neck gaiter are common in many places as they are convenient to wear. Infact, the reason why they are convenient is that they don’t restrict air. Thus, they are of not much use to people.

An N95 mask that has an exhalation valve failed to measure up. Warren mentioned that the relief valves are fantastic if you want to protect yourself from the outside world but, air doesn’t pass through them. If you want to protect the outside world from you, then it completely defeats the purpose.

The CDC updated its guidelines regarding masks. It doesn’t recommend the use of coverings that have valves and vents. CDC wrote, wearing this type of mask won’t prevent people from transmitting the coronavirus to others.

Warren asked people to assess their face covering with the help of another basic test.

If you can see through it when you put it up in the light and you can blow through it easily, then it probably won’t protect anyone.