How does an N95 mask protect against pathogens?

Mar 19, 2020 • 6:28 PM UTC

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Adam Larson

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What is in an N95 mask, and how does it protect our healthcare workers against microscopic pathogens? To find out I deconstructed a broken N95 mask.

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The mask is composed of 4 layers, the bottom being the layer most exposed to external environments. They are bonded together on the exterior. Inner layers are often treated with metal ions which interact with viral particles to trap them inside. These masks are rated to trap most particles (95%) that are larger than 300µm. This is why they are most needed by healthcare workers in pathogen filled environments.

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The outer layer has fairly thick fibers of polypropylene and perforations.

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Inside the mask, beyond the outer layer, is a stiff layer of large polyester fibers.

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Behind this stiff layer of large filaments is a very dense pillowy network of melt blown polypropylene. This would be the main protection against submicron sized particles.