Now we come to the bottom of the barrel, the things that are technically “face coverings” but that don’t fit as snugly or provide as many layers of protection as a proper cloth mask. We don’t recommend these in place of more effective masks.
There was a study early in the pandemic that insinuated neck gaiters may be worse than no mask at all, but the evidence for that statement was never very strong. We do know, though, that those gaiters have several features that mean they don’t fit the definition of a good mask. Their fabric is thin, they tend to leak around the sides of the nose, and the threads that make up the fabric form fairly large holes. If you do wear a buff in place of a mask, at the very least double or triple the layers.
Likewise, bandanas and scarves are not snug-fitting enough to do the job, and they’re usually too thin as well. These coverings could go well over another mask, bringing us back to the double-masking category from a few slides back. Adding protection isn’t a bad idea. But don’t count on these on their own.