Last week the CDC published data to back its recommendation for double masking or modifying medical procedure masks for improved fit and protection against droplets from coughs and sneezes. The two masking methods tested by the CDC were:
Wearing a cloth mask over a medical procedure mask - Double Masking
Knotting the ear loops of a medical procedure mask where they attach to the mask’s edges and then tucking in and flattening the extra material close to the face - Knotted and Tucked Mask
Masks tested: A) Medical Procedure Mask, B) Double Masking, C) Knotted and Tucked Mask
Not pictured: Cloth Mask
Can Masks Filter Out Droplets? Yes, they can.
The data shows that both of these methods provide improved performance compared to an unknotted and untucked medical procedure mask. The CDC first measured the number of simulated cough particles that pass through a mask:
Medical Procedure Mask (unknotted and untucked): 56.1%
Cloth Mask: 51.4%
Double Masking: 85.4%
Knotted and Tucked Mask: 77.0%
How Much More Effective Are Double Masking and Knotted and Tucked Masks?
CDC set up two headforms 6 feet apart from each other in a small room (10ft x 10ft x 7ft) and measured the simulated particles passing through the recipient's mask (in some cases, the recipient had no mask). The experiment had multiple combinations of masked/unmasked headforms, and data shows the following:
Graphically, the data looks like this:
So What Does This All Mean?
Good question. The CDC notes a few limitations of their study, including:
They only tested one model of cloth mask and one model of medical procedure mask, so the data may not apply to all of these types of masks available for purchase.