In January 2020, the CDC conducted experimental simulations to examine the degree to which double masking and knotted and tucked medical masking could decrease exposure to simulated respiratory droplets. The authors first simulated cough emission while wearing a 3-ply cotton cloth mask, an untucked 3-ply medical mask, a knotted and tucked medical mask, and double masking (specifically, fitting a cloth mask over an untucked medical mask). They found that double masking blocked the highest portion of the aerosol emitted (~85%), followed by the knotted and tucked medical mask alone (77%), the medical mask alone (~56%), then the cloth mask alone (~51%). Next, the authors simulated cough exposure with various combinations of masking techniques on both the source of the cough and the recipient. The highest proportion of aerosols blocked was with double masking for both source and recipient (96.4%), followed closely by both knotting and tucking medical masks (95.9%). When the recipient was unmasked, double masking of the cough source blocked ~82% of the aerosol and knotting and tucking the medical mask blocked ~63%. When the cough source was unmasked, the recipient double masking blocked 83% and knotting and tucking the medical mask blocked ~65%. These results emphasize the role of properly fitted masks in reducing the spread of COVID-19.