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: 468498

Reported Deaths: 9100
CountyCasesDeaths
Harrison31907468
Hinds30552569
DeSoto29532342
Jackson22868335
Rankin21016355
Lee14393214
Madison13961263
Jones13053215
Forrest12879231
Lauderdale11244292
Lowndes10148171
Lamar9972122
Pearl River8569208
Lafayette8008136
Hancock7110107
Oktibbeha6764117
Washington6756146
Neshoba6350200
Monroe6304156
Warren6267159
Panola6036122
Pontotoc599292
Bolivar5960143
Marshall5917115
Union558885
Pike5424133
Lincoln5192127
Alcorn509388
George454766
Scott447392
Leflore4377138
Tippah431780
Itawamba429192
Prentiss429074
Copiah423883
Simpson4238108
Wayne419663
Tate418999
Adams4174109
Yazoo411486
Sunflower4057104
Covington404891
Marion399699
Leake389784
Coahoma385996
Newton360273
Grenada3489100
Stone342657
Tishomingo320987
Attala318285
Jasper308261
Winston298191
Clay282672
Chickasaw277464
Clarke271784
Holmes257685
Calhoun256939
Smith241546
Yalobusha215447
Tallahatchie213849
Walthall203457
Lawrence202431
Greene202045
Perry195053
Amite191251
Webster191141
Noxubee173437
Montgomery168652
Jefferson Davis164041
Carroll158936
Tunica146533
Benton137531
Kemper136538
Claiborne124134
Choctaw123824
Humphreys122036
Franklin114127
Quitman100925
Wilkinson98335
Jefferson85832
Sharkey61620
Issaquena1916
Unassigned00

Alabama Coronavirus Cases

Cases: 757893

Reported Deaths: 12784
CountyCasesDeaths
Jefferson1082301712
Mobile694251158
Madison47738562
Baldwin35347420
Shelby34758281
Tuscaloosa32576495
Montgomery32249645
Lee21576200
Calhoun19621363
Morgan19061307
Etowah18363413
Marshall17028252
Houston15881337
St. Clair14724270
Limestone13908178
Elmore13812239
Cullman13756228
Lauderdale12909263
Talladega12124200
DeKalb11705220
Walker10047303
Autauga9371119
Blount9272146
Jackson8970132
Coffee8550150
Colbert8229160
Dale8162142
Escambia632298
Tallapoosa6255165
Covington6214153
Chilton6152128
Russell586753
Franklin558292
Chambers5155127
Dallas4569173
Marion4490114
Clarke447070
Pike439188
Geneva415999
Lawrence4002101
Winston399982
Bibb388975
Barbour334667
Marengo317778
Monroe306844
Butler305878
Pickens296166
Henry288550
Randolph288255
Hale282981
Cherokee275649
Fayette268569
Washington241844
Crenshaw226962
Clay219260
Macon211154
Cleburne205746
Lamar184638
Conecuh173337
Lowndes167856
Coosa160031
Wilcox153033
Bullock145642
Perry132430
Sumter122635
Greene117941
Choctaw71925
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