What Is the Best Mask for COVID-19? A Mechanical Engineer Explains the Science After 2 Years of Testing Masks in His Lab

What Is the Best Mask for COVID-19? A Mechanical Engineer Explains the Science After 2 Years of Testing Masks in His Lab

By Christian L’Orange, Colorado State University


The Centers for Disease Control and Prevention has modified its pointers about masks and respirators various instances over the previous two years and gave its most up-to-date replace on Jan. 14, 2022. The replace states that material face coverings provide the least safety from the coronavirus in contrast with surgical masks or N95-style masks. Christian L’Orange is a mechanical engineer who has been testing the efficiency of masks for the state of Colorado because the starting of the pandemic. He explains the brand new CDC pointers and the science of what makes for masks.

1. What modified within the CDC pointers?

The CDC currently recommends that you simply “wear the most protective mask you can that fits well and that you will wear consistently.” The query, then, is what sort of masks presents the most effective safety for you – by filtering the air you breathe in – and for these round you – by filtering the air you breathe out?

The CDC’s up to date pointers clearly lay out the hierarchy of protection: “Loosely woven cloth products provide the least protection, layered finely woven products offer more protection, well-fitting disposable surgical masks and KN95s offer even more protection, and well-fitting NIOSH-approved respirators (including N95s) offer the highest level of protection.”

From a efficiency standpoint, the N95 and KN95 masks are the best option. While supply chain limitations led to the CDC recommending individuals not put on N95s early within the pandemic, right this moment they’re simply obtainable and ought to be your first selection in order for you probably the most safety.

The largest change within the new pointers has to do with material masks. Previous steering from the CDC had mentioned that some material masks might provide acceptable levels of protection. The new steering nonetheless acknowledges that material masks can provide a small quantity of safety however locations them on the very backside of the bunch.

A tangled mass of fibers, as seen through a microscope.

N95 masks are made out of a tangled net of tiny plastic fibers which might be very efficient at trapping particles.
Alexander Klepnev via Wikimedia Commons, CC BY-SA

2. What’s the distinction between N95, surgical and material masks supplies?

The effectiveness of a masks – how a lot safety a masks offers the wearer – is a mixture of two main parts. First, there’s the power of the fabric to seize particles. The second issue is the fraction of inhaled or exhaled air leaking out from across the masks – basically, how nicely a masks suits.

Most masks supplies might be considered a tangled web of small fibers. Particles passing by a masks are stopped once they bodily contact a type of fibers. N95s, KN95s and surgical masks are purpose-built to be efficient at eradicating particles from air. Their fibers are sometimes made out of melt-blown plastics, typically polypropylene, and the strands are tiny – typically lower than four thousandths of an inch (10 micrometers) in diameter – or roughly one third the width of a human hair. These small fibers create a considerable amount of floor space inside the masks for filtering and accumulating particles. Although the particular development and thickness of the supplies utilized in N95, KN95 and surgical masks can fluctuate, the filter media used are sometimes fairly related.

These fibers are very tightly packed collectively so the gaps a particle should navigate by are very small. This leads to a excessive chance that particles will find yourself touching and sticking to a fiber as they go by a masks. These polypropylene supplies additionally typically have a static charge that may assist appeal to and catch particles.

Cloth masks are sometimes manufactured from widespread woven supplies reminiscent of cotton or polyester. The fibers are sometimes giant and fewer densely packed collectively, which means particles can easily pass through the material. Adding extra layers may also help, however stacking layers has a diminishing return and the efficiency of a material masks, even with multiple layers, will nonetheless sometimes not match that of surgical masks or N95.

3. How a lot does match matter for masks?

KN95 face mask

Fit is the opposite main element in how efficient a masks is. Even if the supplies utilized in a masks had been excellent and it eliminated all particles from the air that handed by it, a masks can provide safety provided that it doesn’t leak.

When you breathe out and in, air will at all times take the trail of least resistance. If there are any gaps between a masks and somebody’s face, a considerable fraction of each breath will seep out by these gaps and the masks will provide relatively little protection.

Many material masks designs merely don’t seal nicely. They are usually not stiff sufficient to push towards the face, there are gaps the place the masks doesn’t even are available in contact with the face and it isn’t doable to cinch them tightly sufficient towards the pores and skin to type a good seal.

But leaking is a priority for all masks. Although the supplies utilized in surgical masks are fairly efficient, they typically bunch and fold on the perimeters. These gaps present a straightforward route for air and particles to leak out. Knotting and tucking surgical masks or carrying a material masks over a surgical masks can each significantly reduce leakage.

N95 masks aren’t proof against this downside both; if the nostril clip isn’t securely pushed towards your face, the masks is leaking. What makes N95s distinctive is {that a} specific requirement of the N95 certification course of is ensuring the masks can type seal.

4. What is completely different about omicron?

The mechanics of how masks operate is probably going no completely different for omicron than another variant. The distinction is that the omicron variant is more easily transmitted than earlier variants. This excessive degree of infectiousness makes carrying good-quality masks and carrying them accurately to restrict the probabilities of catching or spreading the coronavirus that rather more crucial.

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Unfortunately, the attributes that make for masks are the very issues that make masks uncomfortable and never very trendy. If your material masks is cozy and lightweight and appears like you’re carrying nothing in any respect, it most likely isn’t doing a lot to maintain you and others protected from the coronavirus. The safety supplied by a high-quality, well-fitting N95 or KN95 is the most effective. Surgical masks might be very efficient at filtering out particles, however getting them to suit accurately might be tough and makes the general safety they are going to present you questionable. If you might have different choices, material masks ought to be a final selection.The Conversation

Christian L’Orange, Assistant Research Professor of Mechanical Engineering, Colorado State University

This article is republished from The Conversation underneath a Creative Commons license. Read the original article.

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