Double masking can block 92% of infectious particles, CDC says

Double masking can significantly improve protection, new data from the US Centers for Disease Control and Prevention shows.Researchers found that laye...

Posted: Feb 10, 2021 1:43 PM
Updated: Feb 11, 2021 11:15 AM

Double masking can significantly improve protection, new data from the US Centers for Disease Control and Prevention shows.

Researchers found that layering a cloth mask over a medical procedural mask, such as a disposable blue surgical mask, can block 92.5% of potentially infectious particles from escaping by creating a tighter fit and eliminating leakage.

'These experimental data reinforce CDC's prior guidance that everyone 2 years of age or older should wear a mask when in public and around others in the home not living with you,' CDC Director Dr. Rochelle Walensky, told a White House briefing.

'We continue to recommend that masks should have two or more layers, completely cover your nose and mouth, and fit snugly against your nose and the sides of your face,' said Walensky

Medical procedure masks like the commonly seen blue surgical masks typically don't fit securely to faces and create gaps, allowing unfiltered air to escape. A fitted cloth mask can act as a cinch and secures the loose medical mask in place. This improves protection by preventing leakage of unfiltered air and particles, better protecting the wearer and those around them.

Double masking and knotting

Beginning in January 2021, the CDC tested two simple modifications to improve the performance of commonly used masks by using the 'double masking' and 'knotting' methods.

The study found that 'knotting' can improve the overall performance of medical procedure masks. By folding mask edges inward and knotting ear loop strings where they meet mask fabric, the excess fabric is flattened and reduces the gap on either side of the face.

A knotted medical mask can block 63% of particles that could contain coronavirus from escaping, a significant improvement from blocking only 42% of particles when unknotted, according to the CDC's Morbidity and Mortality Weekly Report published Wednesday.

The study also found that when both an infected and uninfected source were wearing double masks, the cumulative exposure from potentially infectious aerosols of of the uninfected person was reduced by 96.4%. When both people wore knotted and tucked masks alone, the cumulative exposure was reduced by 95.9%.

Both findings highlight the importance of a good fit to maximize mask performance and reduce exposure.

The CDC team used a medical procedure mask, and a three-layered cloth mask for a total of 12 different mask combinations. They performed tests using various combinations of no mask, double masks, and unknotted or knotted and tucked medical procedure masks. They did not test N95 respirators.

New data is not changing reccomendations

When studying 'double masking' these experiments used one cloth mask over a medical mask. The researchers did not include any other combinations of masks, such as cloth over cloth, medical procedure mask over medical procedure mask, or medical procedure mask over cloth.

'I want to be clear that these new scientific data released today do not change the specific recommendations about who should wear a mask, or when they should wear one. But they do provide new information on why wearing a well-fitting mask is so important to protect you and others,' said Walensky. 'Based on this new information, the CDC is updating the mask information for the public on the CDC website to provide new options on how to improve mask fit.'

Some may see the new CDC research efforts as the first tepid acknowledgement from the federal government that the public needs higher quality masks, that experts and democratic lawmakers have been calling for.

An Axios-Ipsos poll found an all-time high of 72% of Americans say they wear a mask at all times, but some Americans have expressed frustration at the evolving mask guidance responding to the novel coronavirus. Experts point out that 'novel' means new, and as scientists and health officials learn more, recommendations may change.

Dr. John Brooks, chief medical officer of the CDC's Covid-19 response, who worked on the study, described the findings as 'new information for consumers to help them really take control of their risk.'

'If you're going to wear a mask, consider what you can do to make sure that it fits well to improve its performance,' Brooks told CNN.

Masks became an important part of the coronavirus response when it was discovered that the virus could be transmitted by asymptomatic carriers. It was initially a scramble to get people wearing masks last spring, and some experts have spent the last year conducting studies proving masks could prevent the spread of coronavirus. Now that it is known how well masks work, the next step is making them work better, according to Brooks.

'We've never had to think about regulating cloth masks,' Brooks told CNN.

White House press secretary Jen Psaki said Wednesday there's no formal recommendation that people wear two masks, but is considering a 'range of options' when it comes to getting masks to Americans,.

Psaki told reporters during a news briefing that reports that two masks protect better than one were based on a 'study, which was a reflection of the importance of well-fitting masks, something that many of our health and medical experts have talked about.'

'It doesn't actually issue definitive guidance on one mask versus two mask,' Psaki said. 'Obviously if that's something they were to issue as official guidance, we listened to our health and medical experts.'

She said the study shows 'that if a person has a loose fitting mask that they should consider options to improve that fit.'

Consumer mask standards in the works

There are also efforts in the works to create the first US consumer mask standards.

ASTM International, an international technical standards organization, and the National Personal Protective Technology Laboratory, are working on standards help Americans tell which masks actually work,

The National Personal Protective Technology Laboratory is a part of the CDC's National Institute of Occupational Safety and Health (NIOSH).

Brooks indicated that the CDC would encourage or recommend the ASTM standards, but didn't believe the CDC would require them to avoid 'creating barriers.'

He does believe having a consumer mask standard in place could move the manufacturing market in the right direction, which is ultimately what is needed to ensure consumer protection.

'An ASTM approval that you've met their standard, we hope, will push the industry in the direction of being sure they focus on producing masks that actually do what they're supposed to.'

Mississippi Coronavirus Cases

Data is updated nightly.

Cases: 314509

Reported Deaths: 7247
CountyCasesDeaths
DeSoto21626259
Hinds20359415
Harrison17934309
Rankin13634278
Jackson13447246
Madison10099217
Lee9980174
Jones8381163
Forrest7683152
Lauderdale7191241
Lowndes6401147
Lamar623086
Lafayette6200118
Washington5339134
Bolivar4802132
Oktibbeha462798
Panola4588107
Pearl River4512146
Marshall4443103
Warren4393121
Pontotoc420772
Monroe4113133
Union411076
Neshoba4031176
Lincoln3968110
Hancock379386
Leflore3497125
Sunflower336090
Tate334084
Pike3325105
Scott315973
Alcorn313368
Yazoo311669
Itawamba300477
Copiah297065
Coahoma295479
Simpson295288
Tippah288768
Adams286882
Prentiss279760
Marion269280
Leake268373
Wayne262641
Grenada261487
Covington259681
George248048
Newton246861
Winston227281
Tishomingo226967
Jasper221148
Attala214473
Chickasaw207857
Holmes189173
Clay185454
Stone182833
Tallahatchie178841
Clarke178080
Calhoun170832
Yalobusha164338
Smith162434
Walthall133945
Greene130633
Lawrence128624
Montgomery126942
Noxubee126734
Perry126338
Amite123142
Carroll121829
Webster114532
Jefferson Davis107133
Tunica105726
Claiborne102430
Benton99525
Humphreys96733
Kemper95828
Franklin83823
Quitman80916
Choctaw76418
Wilkinson67331
Jefferson65728
Sharkey50217
Issaquena1686
Unassigned00

Alabama Coronavirus Cases

Cases: 532895

Reported Deaths: 11001
CountyCasesDeaths
Jefferson771431528
Mobile41089808
Madison34837505
Tuscaloosa25810454
Montgomery24355588
Shelby23730249
Baldwin21191309
Lee15892171
Calhoun14522316
Morgan14324279
Etowah13861353
Marshall12250223
Houston10581281
Elmore10060205
Limestone9986151
Cullman9705194
St. Clair9702243
Lauderdale9441242
DeKalb8846187
Talladega8255176
Walker7246277
Autauga6938108
Jackson6815112
Blount6694137
Colbert6310134
Coffee5524119
Dale4850111
Russell443238
Chilton4308112
Franklin426282
Covington4136118
Tallapoosa4039152
Escambia393977
Chambers3578123
Dallas3557152
Clarke351161
Marion3130101
Pike311377
Lawrence300798
Winston275673
Bibb261564
Geneva251477
Marengo249664
Pickens234761
Barbour231756
Hale223277
Butler216469
Fayette212562
Henry189044
Cherokee184745
Randolph181742
Monroe178040
Washington167639
Macon159950
Clay156857
Crenshaw152757
Cleburne149141
Lamar142935
Lowndes139053
Wilcox127130
Bullock122841
Conecuh110629
Coosa107928
Perry107826
Sumter104832
Greene92534
Choctaw61124
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