What is the best mask for COVID-19? | Kiowa County Press

Not all masks offer the same level of protection for you and those around you. Martin Barth/EyeEm via Getty Images

Christian L’Orange, Colorado State University

The Centers for Disease Control and Prevention has changed its guidelines on masks and respirators several times over the past two years and released its latest update on January 14, 2022. The update states that face coverings in fabric offer the least protection against the coronavirus compared to surgical masks or N95 type masks. Christian L’Orange is a mechanical engineer which has been testing the performance of masks for the state of Colorado since the start of the pandemic. He explains the new CDC guidelines and the science of what makes a good mask.

1. What has changed in the CDC guidelines?

The CDC currently recommend that you “wear the most protective mask possible that fits you well and that you will wear it systematically”. The question then becomes, which type of mask offers the best protection for you – by filtering the air you breathe in – and for those around you – by filtering the air you breathe out?

Updated CDC guidelines clearly state the hierarchy of protection“Loosely woven fabric products offer the least protection, thinly woven layered products offer more protection, tight-fitting disposable surgical masks and KN95s offer even more protection, and tight-fitting NIOSH-approved respirators (including N95s) provide the highest level of protection.”

From a performance perspective, the N95 and KN95 masks are the best option. While supply chain limits led the CDC to recommend people not wear N95s at the start of the pandemic, today they are readily available and should be your first choice if you want the most protection.

The biggest change in the new guidelines is to cloth masks. Previous CDC guidance had indicated that some cloth masks may offer acceptable levels of protection. The new guidelines still acknowledge that cloth masks may offer a little protection, but put them right at the bottom of the pack.

A mass of tangled fibers, seen under a microscope.
N95 masks are made from a tangled web of tiny plastic fibers that are very effective at trapping particles. Alexander Klepnev via Wikimedia Commons, CC BY-SA

2. What is the difference between N95, surgical and cloth masks?

Mask effectiveness – the level of protection a mask offers the wearer – is a combination of two major elements. First, there is the ability of the material to capture particles. The second factor is the fraction of inhaled or exhaled air that escapes around the mask – essentially, how well a mask fits.

Most mask materials can be thought of as a tangled net of small fibers. Particles passing through a mask are stopped when they physically touch one of these fibers. N95, KN95 and surgical masks are specially designed to effectively remove particles from the air. Their fibers are usually made from melt-blown plastics, often polypropylene, and the strands are tiny – often less than four thousandths of an inch (10 micrometres) in diameter – about a third of the width of a human hair. These small fibers create a large surface area inside the mask to filter and collect particles. Although the specific construction and thickness of the materials used in N95, KN95, and surgical masks can vary, the filter media used are often quite similar.

These fibers are very tightly packed together, so the spaces a particle has to cross are very small. This results in a high probability that particles will end up touching and sticking to a fiber as they pass through a mask. These polypropylene materials also often have a static load which can help attract and catch particles.

Cloth masks are usually made from common woven materials such as cotton or polyester. The fibers are often coarse and less dense, which means that the particles can easily pass through the material. Adding more layers can help, but stacking layers has a diminishing returns and the performance of a cloth mask, even with multiple layerswill generally not match that of the surgical mask or N95.

A side view of a man wearing a surgical mask
Surgical masks are made of good materials but are difficult to seal against the face and often allow air to escape through a person’s cheeks. Krisanapong Detrapphiphat/Moment via Getty Images

3. How important is fit for masks?

Fit is the other major component of a mask’s effectiveness. Even if the materials used in a mask were perfect and removed all particles from the air passing through it, a mask can only offer protection if it does not leak.

As you inhale and exhale, the air will always take the path of least resistance. If there are spaces between a mask and someone’s face, a substantial fraction of each breath will seep through those spaces and the mask. offer relatively little protection.

Many fabric mask designs simply don’t seal well. They’re not stiff enough to push against the face, there are gaps where the mask doesn’t even come into contact with the face, and it’s not possible to squeeze them tight enough against the skin to form a decent seal.

But leaks are a concern for all masks. Although the materials used in surgical masks are quite effective, they often bunch up and bend at the sides. These gaps allow air and particles to easily escape. Tying and tucking surgical masks or wearing a cloth mask over a surgical mask can both drastically reduce leaks.

N95 masks aren’t immune to this issue either; if the nose clip is not pressed firmly against your face, the mask will leak. What makes the N95s unique is that a specific requirement part of the N95 certification process is to ensure that the masks can form a good seal.

4. How is omicron different?

The working mechanism of the masks is probably no different for omicron than for any other variant. The difference is that the omicron variant is transmitted more easily than the previous variants. This high level of infectivity makes wearing good quality masks and wearing them correctly to limit the risk of catching or spreading the coronavirus all the more critical.

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Unfortunately, the attributes that make a good mask are precisely those that make masks uncomfortable and unsightly. If your cloth mask is comfortable and light and you feel like you’re wearing nothing at all, it’s probably doing little to protect you and others from coronavirus. The protection offered by a high-quality, well-fitting N95 or KN95 is the best. Surgical masks can be very effective at filtering out particles, but fitting them correctly can be tricky and makes the overall protection they will provide you questionable. If you have other options, cloth masks should be a last choice.

The conversation

Christian L’Orangeassistant professor-researcher in mechanical engineering, Colorado State University

This article is republished from The conversation under Creative Commons license. Read it original article.

About Florence M. Sorensen

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