Researchers at Duke tested how well different types of masks stopped the spread of saliva droplets coming from people’s mouths when they spoke. They found that N95 masks without valves work best followed by surgical masks. Cotton masks did stop the spread of some droplets from speech, while bandanas and neck fleeces like balaclavas did almost nothing. This study suggests that wearing an N95 mask or a surgical mask might best help slow the spread of the coronavirus.