Alliance for Pandemic Preparedness

February 10, 2021

Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021

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The CDC found that fitting a cloth mask over a medical procedure mask (double masking), and knotting the ear loops of a medical procedure mask, then tucking in and flattening the extra material near the face substantially improves the efficacy of masks. In simulated coughing experiments, the unknotted medical procedure mask blocked 42% of the particles from a cough, the cloth mask blocked 44%, and double masking blocked 93% of the particles. The cloth mask plus medical mask or the knotted and tucked mask reduced the cumulative exposure of the unmasked receiver by 82% and 63%, respectively. When the source was unmasked and the receiver wore a double mask or the knotted and tucked mask, the receiver’s cumulative exposure was reduced by 83% and 65%, respectively. When both source and receiver wore double masks or knotted and tucked masks, the cumulative exposure of the receiver was reduced by 96%.

Brooks et al. (Feb 10, 2021). Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021. MMWR. https://doi.org/10.15585/mmwr.mm7007e1