What’s up with the new CDC mask study?

Masks Staying Safe

A: Good news, double-masking or tightening up ear loops works!

Remember the key features of effective masking: FILTERING and FIT.

The U.S. Centers for Disease Control and Prevention (CDC) released a new experimental study testing ways to improve mask fit for cloth and medical masks to reduce leakage around the edges.
Using mannequin “headforms” and simulated coughing they tested:

1) Cloth mask over a medical mask (double masking)

2) Medical mask with knotted ear loops and tucked in sides.

The experiment was able to test both source control (how well the masks blocked outward coughing) and exposure for the “receiver” breathing in aerosols.

% Reductions in aerosol exposures for the “receiver” compared to no masks were ⚡IMPRESSIVE⚡:

UNKNOTTED MEDICAL MASK (source/receiver):

no mask/mask = 7.5%,
mask/no mask = 41.3%
mask/mask = 84.3%


no mask/mask = 64.5%
mask/no mask = 62.9%
mask/mask = 95.9%

DOUBLE MASK (source/receiver):

no mask/mask = 83.0%
mask/no mask = 82.2%
mask/mask = 96.4%

💥These experiments provide evidence that FIT can greatly improve the effectiveness of any mask you are wearing.

🤔 Caveats: While the experiment was designed to mimic conditions for transmission, it did not use real people or real virus (thankfully we are not allowed to such experiments). Thus, these numbers should be interpreted as a good indication of the ability of the masks to block particles of the size that carry SARS-CoV-2, but not precise measures of transmission itself.

➡️ As we continue our marathon race of vaccinating towards population immunity, good fitting masks are great tool to help deny the virus the new hosts it wants to keep reproducing (and mutating).

➡️ The more we can create “dead ends” for the virus, the faster we can end this pandemic!

Those Nerdy Girls


Full CDC study

Video instructions for Knotting medical masks

Check our recent DP cheat sheet for best masks

Link to original FB post