Bandannas, gaiters and knitted masks are some of the least effective face coverings for preventing the spread of coronavirus, according to a new study.

Researchers at Duke University made the discovery while testing 14 different types of masks, according to the study published Friday.

N95 masks, often used by healthcare professionals, worked best to stop the transmission of respiratory droplets during regular speech.

Other good performers at stopping leakage were three-layer surgical masks and cotton masks, which can be made at home, the researchers with Duke’s physics department found.

But while bandannas and knitted face coverings may be a unique look, they did not offer much protection, according to the study.

The scientists also discovered that neck fleeces, or neck gaiters, often worn by runners, were the least effective and actually allowed more respiratory droplets to escape than not wearing a mask at all.

“We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work.”.

To test the masks, the scientists made use of a black box outfitted with a laser and a cell phone camera.

Someone wearing a face mask would speak in the direction of the laser beam inside the box.

Then, the amount of respiratory droplets scattered by the beam were recorded by the camera in the back of the box.

The researchers said this was a low-cost, effective method to test which face coverings worked and which didn’t.

“This is a very powerful visual tool to raise awareness that a very simple masks, like these homemade cotton masks, do really well to stop the majority of these respiratory droplets,” Fischer told CNN?