This stops any air leaks around the edges. Good respirator masks usually have 2 bands that go over your head so that they pull the edges of the mask close against your face. This means that the air you breathe in and out is filtered. When properly fitted to your face, a respirator mask forces all the air you breathe to go through the mask. Properly worn, a respirator mask gives you better protection against inhaling aerosols than a medical mask. They may not work well for children because their faces are smaller. Respirator masks do not work well on people with a lot of facial hair. They are usually white on the inside and the outside.įFP2, FFP3, N95 and KN95 are all types of respirator masks. As people continue to wear fabric masks to limit the spread of COVID-19, or if the need should arise again in the future, these tiny details will help.Respirator masks often have 4 layers of light, paper-like material. NIST scientists are still working to gain a better understanding of the filtration properties of mask fabrics. The NIST studies described on this page and studies by other organizations contributed to the development of those standards, which will give people in nonmedical fields information on how well their masks work. The first standards for fabric masks were recently released. Their filtration performance is well known because there have long been standards for medical grade masks. N95 respirators get their name because they filter out 95% of particles that are 0.3 millionths of a meter in size. The fibers are far smaller and have much greater surface area than cotton fibers, which is one reason this is an especially effective filtering material. The filtering material is made by melting and then air-blowing polypropylene, a type of plastic, into a chaotic web. This layered structure then repeats for added protection. This false-color image shows a cross section of one layer of an N95 respirator mask, including filtering material, shown in purple, and protective material around it. While cotton is best for the fabric masks that the general public uses, medical-grade masks are a different story. As microscopic particles pass through, they absorb some of this moisture and grow larger, which makes them more likely to get trapped. In addition, cotton fibers are hydrophilic, meaning they like water. By absorbing small amounts of the water in a person’s breath, cotton fibers create a moist environment inside the fabric. This increases the amount of surface area that an aerosol can stick to. Seen up close, cotton fibers have kinks and bends. The Star Destroyer couldn’t make it through. Only the smaller ships could turn fast enough. NIST researcher Chris Zangmeister likens this to the scene in Star Wars: The Empire Strikes Back when starfighters are streaking through the asteroid field. As the air bends and twists around the fibers, some of the aerosols can’t turn fast enough and smash into and stick to them. The aerosols can be very small, but they do have some mass. When you breathe through a mask, the air flows around these fibers and the aerosols are pulled along for the ride. This image shows the individual fibers in cotton flannel. Vicenzi/Smithsonian's Museum Conservation Institute and NIST And they can give us all a sense of the beautiful, textured, woven world right in front of our faces.Į.P. His images gave the scientists important insights into the particle-filtering properties of different fabrics. He is also a visiting researcher at NIST. Vicenzi works at the Smithsonian’s Museum Conservation Institute, where he studies the history and origin of objects in the museums’ collection. After being exposed to the moisture in a person’s breath, cotton fabrics perform better still.Īs part of this research, one team member, Edward Vicenzi, used a scanning electron microscope to examine the fabrics up close. Their research indicates that that cotton fabrics tend to perform better than synthetics, with cotton flannels being particularly effective. The researchers wanted to know how well different fabrics filter out those particles and what makes some fabrics better filters than others. Those masks work by blocking some of the virus-filled droplets and smaller particles, called aerosols, that an infected person exhales, and they also offer some protection to the wearer by filtering incoming air. To understand how something works, it helps to see it up close.Ī team of researchers took this approach when studying the fabric masks that people wear to slow the spread of COVID-19.

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