Reusable Masks and the Fabrics that Actually Work

 

We now know from recent studies that a significant portion of individuals with coronavirus lack symptoms (“asymptomatic”) and that even those who eventually develop symptoms (“pre-symptomatic”) can transmit the virus to others before showing symptoms. This means that the virus can spread between people interacting in close proximity—for example, speaking, coughing, or sneezing—even if those people are not exhibiting symptoms. 

The Centers for Disease Control and Prevention updated its guidance on the matter, recommending individuals use cloth face coverings "in public settings where other social distancing measures are difficult to maintain," such as grocery stores and pharmacies. The guidance recommends people use fabric coverings, not surgical masks or specialized N95 masks, which should be reserved for health care providers.

If you are making your own covering, new research finds that some fabrics are better than others at filtering out viral particles.

"You have to use relatively high-quality cloth," Dr. Scott Segal, chair of anesthesiology at Wake Forest Baptist Health in Winston-Salem, North Carolina, said.

Face coverings made of fabric, public health experts note, aren't intended to protect wearers from getting sick, but rather, to prevent them from spreading the virus to others.

In partnership with the Wake Forest Institute for Regenerative Medicine, Segal tested a variety of cloth materials to see which ones not only allowed for breathability, but also filtered small particles — such as viruses. 

To test various masks and fabrics, the team pumped air through both types of face coverings.

"Our instruments could read down to 0.3 microns, which is about the size of a big virus," Segal said.

Regular surgical masks filtered out 62 percent to 65 percent of particles. For comparison, N95 masks filter 95 percent of those particles.

But the fabrics led to a variety of results. One piece of cloth filtered just 1 percent of particles, rendering it virtually useless, while others were found to perform even better than the surgical masks.

"We had some that performed at 79 percent," Segal told NBC News.

The best masks were constructed of two layers of heavyweight "quilters cotton" with a thread count of at least 180, and had thicker and tighter weave.

Other hospitals, such as Vanderbilt University Medical Center in Nashville, have also suggested using tightly woven fabrics for do-it-yourself facial coverings. Kaiser Permanente has also published instructions on DIY masks, also calling for two layers of cotton fabrics.

Cotton T-shirts, however, may not be as useful. A 2013 study published in the journal Disaster Medicine and Public Health Preparedness compared medical grade surgical masks with homemade facial coverings using plain cotton T-shirts. The surgical masks were found to be three times more effective in blocking small particles than the T-shirts. 

So choose your fabrics wisely if you are making or purchasing a cloth mask. What may be fashionable isn't always effective.