Which face masks are the most (and least) effective at stopping COVID-19 exposure?

August 12, 2020


A new Duke University study examined a variety of masks to see which are most effective at blocking respiratory droplets to protect wearers and the people around them.


  • Surgical N95. This mask is manufactured to surgical standards to provide a tight seal around the face. However, because of a shortage, most experts ask members of the general public to avoid acquiring these masks so they can be reserved for health professionals.
  • Three-layer simple surgical mask. Widely available and found to provide the next-highest level of protection.
  • Cotton. The researchers examined several different types of cotton masks and found most of them were fairly effective, but described the best as a “Cotton-polypropylene-cotton mask.”
  • Fleece: The study found that this type of face covering is worse than no mask at all. The researchers found that fleece face coverings – for example, a gaiter neck fleece – actually break up respiratory droplets into smaller droplets rather than blocking them, releasing a larger number of individual droplets into the air. Those smaller droplets are lighter in weight and therefore stay airborne longer. “Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive,” the researchers wrote.
  • Bandanas were also considered ineffective, though not quite as bad as no mask at all.
  • Knitted: These types of masks were not effective at blocking respiratory droplets.

    Below are the range of masks that the Duke study tested.

    (Duke University)


    Duke researchers say, naturally, the most effective mask was the N95. The Centers for Disease Control and Prevention explains that N95 are not only masks, but respirators that filter out at least 95% of particles in the air. N95s also fit more securely than a regular face mask does, allowing for minimal leakage.