It's not clear that a scarf's effectiveness at blocking tiny particles makes it good at protecting the wearer from those particles. Consider the case where you

It's not clear that a scarf's effectiveness at blocking tiny particles makes it good at protecting the wearer from those particles. Consider the case where you're on a flight with someone who's got COVID-19 and is coughing. The scarf blocks 50% of the particles a surgical mask would block. You then spend the rest of the flight breathing in and out through the scarf that blocked those particles. Does wearing the scarf lower your risk, leave it unchanged, or actually raise it?