U.S. CDC says double masking could boost COVID-19 protection

different types of protective face mask against blue background
different types of protective face mask against blue background

U.S. Centers for Disease Control and Prevention Wednesday released a new coronavirus report showing the benefits of improved mask wearing. According to the report, double masking or knotting the ear loops for surgical masks to create a tighter fit can boost COVID-19 protection

In January 2021, the CDC conducted various experiments to assess two methods of improving medical procedure mask performance by improving fit and, in turn, filtration.

The first being double masking and the other knotting and tucking the medical procedure mask. The first experiment assessed how effectively various mask combinations reduced the number of particles emitted during a cough in terms of collection efficiency.

A pliable elastomeric headform was used to simulate a person coughing by producing aerosols from a mouthpiece (0.1–7 μm potassium chloride particles). The effectiveness of the following mask configurations to block these aerosols was assessed: a three-ply medical procedure mask alone, a three-ply cloth cotton mask alone, and the three-ply cloth mask covering the three-ply medical procedure mask (double masking).

The second experiment assessed how effectively the two modifications to medical procedure masks reduced exposure to aerosols emitted during a period of breathing. A knotted and tucked medical procedure mask is created by bringing together the corners and ear loops on each side, knotting the ears loops together where they attach to the mask, and then tucking in and flattening the resulting extra mask material to minimize the side gaps. A modified simulator with two pliable elastomeric headforms (a source and a receiver) was used to simulate the receiver’s exposure to aerosols produced by the source.

Results from the first experiment demonstrated that the unknotted medical procedure mask alone blocked 42.0% of the particles from a simulated cough (standard deviation [SD] = 6.70), and the cloth mask alone blocked 44.3% (SD = 14.0). The combination of the cloth mask covering the medical procedure mask (double mask) blocked 92.5% of the cough particles (SD = 1.9).

In the second experiment, adding a cloth mask over the source headform’s medical procedure mask or knotting and tucking the medical procedure mask reduced the cumulative exposure of the unmasked receiver by 82.2% (SD = 0.16) and 62.9% (SD = 0.08), respectively. When the source was unmasked and the receiver was fitted with the double mask or the knotted and tucked medical procedure mask, the receiver’s cumulative exposure was reduced by 83.0% (SD = 0.15) and 64.5% (SD = 0.03), respectively. When the source and receiver were both fitted with double masks or knotted and tucked masks, the cumulative exposure of the receiver was reduced 96.4% (SD = 0.02) and 95.9% (SD = 0.02), respectively.


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