A safer way to mask off COVID-19

Coronavirus Outbreak

ROCHESTER, N.Y. (WROC) — The Centers for Disease Control and Prevention (CDC) has released new information about making medical masks more effective. Dr. Jeff Harp of Highland Family Medicine talking about the CDC’s findings and what they might mean for you.

The CDC released information about making medical masks more effective last week. What is it?

During January 2021, the CDC conducted experiments to assess two ways of improving the fit of medical procedure masks: fitting a cloth mask over a medical procedure mask or “doubling” and knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face, or “tying.” Each modification substantially reduced exposure from infected wearers (source control) and reduced exposure of uninfected wearers (wearer exposure).

What specific types of masks were used?

Both the medical procedure masks and the cloth mask used were 3-ply, meaning they had three layers. For cloth masks, that means three layers of cloth. For medical procedure masks it means that if you cut open your mask, you should see a very obvious three layers. The three layers would typically consist of an outer hydrophobic non-woven layer (translucent), a middle melt-blown layer (white), and an inner soft absorbent non-woven layer (green, blue, or white).

What were the results?

The experiments were done in two groups using manikins to simulate cough and cough exposure. The first experiments looked at particles generated by a cough. They showed that either mask alone blocked a little more than 50% of the particles from a simulated cough. Double masking blocked 85% of the cough particles and tying blocked 75%.

And the second group?

The second experiment looked at particles received by someone exposed to a cough. When the cougher was masked, doubling reduced exposure of an unmasked receiver by 80%, and knotting and tying reduced the exposure by 60% compared with wearing the medical mask alone. When the cougher was unmasked and the receiver mask was doubled the receiver’s cumulative exposure was reduced by 83.0%, and when the receiver mask was tied exposure was reduced by 64.5%. When the cougher and receiver both wore doubled or tied masks the cumulative exposure of the receiver was reduced 95% or more compared with wearing an unmodified medical mask alone.

What are the implications for public health?

These experiments highlight the importance of good fit to maximize the effectiveness of a medical procedure mask. Fit can be improved by wearing a cloth mask over a medical mask or by tying it. Employers are beginning to modify their masking policies to allow these techniques in the workplace when they do not otherwise interfere with job duties. Other techniques which improve fit but were not examined in this study include mask fitters and nylon coverings.

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