Duke University did a study on a variety of face coverings to see which ones blocked the most respiratory droplets, since that’s how COVID is spread.
Doing the best job are the non-valved N95s and surgical masks, circled in yellow
Next best are masks made with the plastic fiber polypropylene, circled in orange. Third best cotton masks are the cotton masks circled in blue, even the valved N95s didn’t do too bad as you can see on the chart below. But the type of face covering that made MORE droplets than before OUTSIDE the mask? Fleece neck gaitors! See it with the red NO circle in the photo!
Researchers think the fleece breaks down the droplets into smaller ones that make it through the mask, and are lighter so they float around the air longer! Check out the whole article from Science Alert!