Ideally, everyone (not just medical workers) should be using a KN95 or N95 mask for optimal protection when COVID cases are high or when there's a contagious variant like Omicron, according to the ...

N95 masks are the most protective because they seal tightly around the nose and mouth so that few viral particles seep in or out. They also contain tangled fibers to filter airborne pathogens ...

An N95 mask blocks against 95% of fine particles ... Hazardous and very unhealthy levels (purple) indicate there is a higher risk of serious health effects for the entire population.