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US government researchers announced the results of another study that showed that wearing two masks is an effective strategy to slow the spread of COVID-19, but has not announced any changes to the mask recommendations.

Dr. John Brooks, an epidemiologist at the Centers for Disease Control, told the Associated Press that a 3-layer or cloth mask can block 40% of particles when inhaled and 80% when exhaled. In contrast, a double-layer mask can block 95% of particles when inhaling and exhaling.

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This update follows President Biden’s chief medical adviser, Dr. Anthony Fauci, telling NBC that double cover is “common sense”. Research by Virginia Tech and Chicago's Advocate Aurora Health reached similar conclusions.

The CDC website specifically recommends double masking by placing a cloth mask on a disposable surgical mask. This strategy is most effective when the edges of the mask are tightened, forcing more air through the filter instead of escaping from the side. A pleasant side effect of tightening the seal (in addition to the obvious benefit of avoiding potentially deadly viruses) is that it is less likely to fog corrective lenses.

The CDC also stated that it will soon remove the "homemade masks" page based on outdated information.

During the pandemic, the official recommendations for wearing masks have changed, starting with a clear requirement that people not wear masks, and changing to early April 2020.

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This change is due to emerging evidence about the efficacy of masks and a shortage of materials needed to produce N95 masks and other personal protective equipment (PPE). As the awareness of the virus increases and the production of masks increases, the guidelines are constantly evolving. No important research has found that wearing masks is ineffective or puts the wearer at higher risk.

Joshua Sargent is the senior news editor of the Hearst Newspapers Department of Commerce. His works involve music, film and television, public health, and cast iron pots. He can also play the guitar solo in Steely Dan's "Kid Charlemagne", which is almost completely correct. He lives in Brooklyn, New York with a cat that "belongs" to him by "law".

Email him at josh.sargent@hearst.com.