That from NIOSH. When pandemic masking started last year, I thought it was idiotic that I was asked not to wear my normal valved N95s, but was told that a single layer Buff gaiter was totally kosher. The CDC has justified my feelings:
As source control, findings from NIOSH research suggest that, even without covering the valve, N95 respirators with exhalation valves provide the same or better source control than surgical masks, procedure masks, cloth masks, or fabric coverings. In general, individuals wearing NIOSH-approved N95s with an exhalation valve should not be asked to use one without an exhalation valve or to cover it with a face covering or mask.
In 2021, equipping anything other than an N95/KF94/KN95, or other equivalent, in an attempt to protect oneself or others is just ritual.