The CDC updated their guidance on August 7, 2020, to indicate that that N95 respirators with valves or vents do not prevent the person wearing the respirator from spreading COVID-19. These types of respirators are designed for dusty construction work and the valve releases droplets into the air.
Similarly, a recent study from Duke University found that “mask alternatives, such as neck fleece [also known as gaiters] or bandanas, offer very little protection.” The researchers explain, “We noticed that speaking through some masks (particularly the neck fleece) seemed to disperse the largest droplets into a multitude of smaller droplets. Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a face covering might be counterproductive.”
Considering the CDC guidance and research findings, we don’t recommend the use of respirators with vents or valves, bandanas or neck gaiters as face coverings at this time.