A new mask study by the US CDC has updated the guidelines for those considering dual mask or if they should buy N95 face protection, as preventing the spread of COVID-19 by aerosols from infections remains a key strategy to deal with the pandemic ongoing. Masks are now not only encouraged by public health officials, but actually required in some situations; however, evolving science and lack of standards have contributed to the confusion as to what people should wear and when.
More recently, this is centered on the possibility of a double mask: that is, using two masks, layers one over the other. It is an approach that has not been officially recommended until now by the US Centers for Disease Control and Prevention, although top officials like Dr. Anthony Fauci have endorsed the practice.
Now, in a new study organized and published by the CDC, some of the challenges and requirements of masking have been put to the test. In particular, the experiments looked at how the most commonly available options – such as cloth masks and medical procedure masks – could be improved, helping to bring their effectiveness closer to that of N95 masks and the like.
The N95 mask standard effectively requires such a face mask to provide at least 95 percent 0.3 micron particle filtration. Similar standards, such as KN95, also require this degree of filtration. Production bottlenecks, however, have led to recommendations that, at least for the general public, alternative facial coatings should be used.
The key here, the new study found, is adjustment. “The CDC conducted experiments to evaluate two ways to improve the fit of medical procedure masks: placing a cloth mask over a medical procedure mask and knotting the handles of a medical procedure mask and then attaching and flattening the extra material close to the face ”, summarized the study, released today. “Each modification has substantially improved control of the font and reduced user exposure.”
Using laboratory tests with mannequins, the CDC experimented with both cloth masks worn over medical procedure masks and medical procedure masks with knotted ear loops and tucked-in sides. Both approaches have effectively improved the seal around the user’s face. Exposure to potentially infectious aerosols has decreased, says the CDC, by about 95 percent for well-fitting masks.
It is a considerable improvement as well. In one experiment, a knotless medical procedure mask, used alone, was shown to block 42% of the particles in a simulated cough. A cloth mask used alone was slightly better, with 44.3% effectiveness.
However, when the cloth masks were combined with the medical procedure mask, the first on top of the second, this double mask blocked 92.5% of the cough particles.
Other options that showed improvements in the fit included the so-called mask adjuster, which helps to shape the mask to the contours of the face, and a nylon cover stretched over the top of the mask. Both do pretty much the same thing: they minimize the gaps through which aerosols can get in and out.
The performance of the mask – and how it is communicated to the public – has received increasing attention during the pandemic. The scarcity of N95-rated facial coatings has led to a huge increase in alternative masks, ranging from homemade fabric coatings to more complex arrangements. However, with little in the way of validating their performance or safety, this left consumers to effectively defend themselves when making an economic selection.
The answer could, at least in part, depend on a proposed new mask pattern. Presented earlier this month by the technical standards organization ASTM International in conjunction with the National Personal Protective Technology Laboratory, the new classifications would effectively fall below the N95 as it currently exists, offering less filtration safety, but with the promise of easier fabrication and therefore , greater availability and accessibility.
Two of these patterns have been proposed, differing in the degree of blocking for 0.3 micron particles they offer. Level 1 would require 20% filtration, but promised more breathability when using the mask. Level 2, in turn, would require at least 50 percent filtering of the masks, but it would be a little more difficult to breathe.
Even with the double mask, however, the CDC warns that it is not completely simple. To begin with, the new study was completed with a single type of medical procedure mask and a single type of tissue mask; other types, brands and styles may vary in performance. The researchers also did not explore other combinations, such as cloth on cloth or medical procedure mask on cloth.
The shapes, sizes and hair of the face can also affect the fit: those with beards, for example, may have difficulty, while children and those with smaller faces may also face extra challenges. Finally, there is a possibility that adjustments made to ensure a tighter fit can also “prevent breathing or obstruct peripheral vision for some users”, allows the study, or adjust the shape of the mask so that it no longer covers the nose and the mouth.