Simple Test Shows Which Face Masks Are Best

When it comes to face masks, not all are equally effective, a new study finds.

Duke University researchers developed a way of testing various types of masks to see which did the best job of stopping droplets coming from people's mouths, preventing spread of the new coronavirus.

They relied on a makeshift apparatus consisting of a box, a laser, a lens and a cellphone camera.

"We confirmed that when people speak, small droplets get expelled, so disease can be spread by talking, without coughing or sneezing," said Martin Fischer, a chemist and physicist at the Durham, N.C., campus. "We could also see that some face coverings performed much better than others in blocking expelled particles."