CDC warned the public against wearing valved facemasks — while recommending them to health workers

The public guideline to avoid valved masks may have something to do with the airline industry’s influence

Published August 22, 2020 2:00PM (EDT)

FFP2 respirator mask with air filtering valve (Pierre Teyssot/AGF/Universal Images Group via Getty Images)
FFP2 respirator mask with air filtering valve (Pierre Teyssot/AGF/Universal Images Group via Getty Images)

The politicization of science in the Trump era –– from the manipulation of the National Weather Service to the suppression of information on climate change at the Environmental Protection Agency –– has been as spectacular as it has been horrific. The latest and most peculiar example comes from the Centers for Disease Control and Prevention (CDC), once the standard for science that informs and shapes health policy in the US and around the world.

In a recent update to its recommendation regarding facemasks, which made national news, the CDC recommended that Americans not wear valved masks. These types of facemasks have a piece of plastic embedded in the fabric with a one-way valve that opens when you exhale and closes when you inhale.

Certainly amid the pandemic there is a great deal of confusion about masks. Yet the agency's latest guidance adds to the confusion rather than clarifying it. In fact, the agency's updated guidance contradicts years of their own safety advice to health care workers; indeed, the CDC's website features a database that includes more than 600 models of valved facemasks recommended for health care settings.

Moreover, the agency admits that it updated the policy without any new data. Peculiarly, the new CDC guidance in early August aligns with a Delta Airline company policy issued in July. Like the CDC guidance update that followed, Delta's earlier policy rejects valved N95 respirators while accepting the wearing of bandannas and neck gaiters — which offer far less protection to the wearer and to those around them.

How valved masks work

On its surface, the agency's logic for this appears to make sense. Valved masks release a small amount of exhaled air, which, if a person has coronavirus, could be virus-ridden air — thus possibly putting those immediately nearby at risk.

While it is true that a small amount of unfiltered air escapes through the valves, there is scant scientific evidence studying how much and how high the risk is. One well-publicized paper (by Duke University physicists), released after the CDC mask guidance change, indirectly looked into the matter. The Duke paper was not actually a comparative study of the efficacy of masks — it merely examined a potential method to do that. This trial of a methodology had a tiny sample size and looked at only one model of valved mask. In any case, it suggested that, in comparison with the "gold standard" of respiratory protection (an N95 respirator without a valve), an N95 with a valve "can decrease protection" for those around the wearer, but is overall far better at stopping viral spread than a bandanna or neck gaiter – two other types of ersatz masks that the CDC does recommend. Indeed, the Duke scientists found that bandannas and neck gaiters "offer very little protection." In any case, since scientific research doesn't seem to have influenced the CDC's guidance, the question remains as to why the CDC suddenly recommended against valved masks. The answer may have something to do with the work of airline industry lobbyists. But the media coverage of the CDC's guidance has largely eclipsed the connection.

The media comes for valves

After the CDC's recommendation against valved masks, the media hyped the news as if the science were settled. One headline at Fox News read: "Avoid wearing coronavirus face masks with vents, valves, CDC says in updated guidance." CNN writes: "Do Not Wear Masks With One Way Valves or Vents"; The Washington Post concludes: "Face masks with valves or vents do not prevent spread of the coronavirus, CDC says."

To be fair, no face covering, short of a properly-fitted N95 respirator, can claim to completely prevent coronavirus' spread. Surgical masks are not designed to create a perfect seal, or to filter out 95 percent of virus particles, and they cannot be fit-tested. Those masks, as well as loose-fitting cotton masks, leave gaps that leak air. They could also leak virus particles, as people breathe in and out. It doesn't take scientists in a lab to see this. Look at just about any random group of mask-wearing people in a store or on the street and observe that large gaps beside the nose or under the ears are visible, and that these are obviously far larger and probably of far greater consequence than the tiny vents on an exhale valve. The zealous focus on valves seems to be a case of missing the forest for a few trees.

Thus it may not be a surprise that the CDC guidance, revised August 7, aligns with the aforementioned Delta Airlines facemask policy dated July 25 that banned valved N95 respirators and any other masks with valves from flights. Delta based its policy on the fear that valves may leak virus particles through a tiny vent. Fair enough. But surgical masks, cotton masks, bandannas, and gaiters all allow particles to get directly through their material, as well as through gaps and leaks around the sides. The updated CDC guidance, which is not based on any new data, contradicts advice the agency has been giving to health care workers for years – and the advice it continues to give them on its own website.

In any case, the extensive media coverage about valved masks ignored that CDC documents published in February — reviewed by the CDC's National Institute for Occupational Safety and Health (NIOSH) on April 9, and updated by the CDC's National Personal Protective Laboratory on August 3 — contradict its new guidance, issued on August 7. That new guidance followed a lobbying campaign by the airline industry.

The next day, in an updated Q&A for health care workers regarding Personal Protective Equipment, the CDC cautioned against wearing a valved respirator to protect against the novel coronavirus, "until data are available to describe how effective respirators with exhalation valves are in preventing the spread of SARS-CoV-2 from the wearer to others." In other words, they cite no data on the alleged dangers from valved respirators; seemingly, they had none. No one did.

The CDC's contradictory advice

3M, the principal manufacturer of N95 respirators, stated in June that they were "not aware of any studies on whether airborne germs exit a respirator through the exhalation valve." They added that as of June, the CDC, NIOSH, and WHO had issued "no guidance on this issue." But 3M noted that the valve does not open far, and that some particles would stick to the valve's membrane rather than exit.

In this same FAQ updated August 8, the CDC stated that because N95s without exhalation valves make it "more difficult to breathe" and may be "hot and uncomfortable," hospitals may want to "consider having employees who are not doing surgery, not working in a sterile field, or not potentially exposed to high velocity streams of body fluids wear a standard N95 with an exhalation valve."

So health care workers may be forgiven if they disregard the CDC's general recommendation against valved respirators. Some may choose to cover their valved respirators with surgical masks or pieces of cloth as an added precaution, as the CDC suggests; others may not because they need to breathe. However, 3M points out that "taping over or otherwise covering a respirator valve voids the regulatory approval and may impact how the respirator functions."

The National Institute for Occupational Safety and Health (NIOSH) agrees. NIOSH, which is the division of the CDC that approves N95 respirators, stated in June that "the effect of any coverings on N95 respirator filtration, fit, or comfort over a prolonged period has not been explored." NIOSH pointed out that such a covering could interfere with a proper fit and seal and "may lead to leaks." Therefore, "covering an N95 mask with either a cloth or surgical mask is not recommended by NIOSH." So in addition to the CDC's ongoing recommendation of valved N95 respirators to health care workers, this is another example of how the CDC's updated guidance on N95 respirators with valves directly contradicts the recommendations of its own experts. 

Concern about dangerous leakage in valved masks is unfounded in both directions –– both inflow and outflow. Indeed, the CDC website still advises health care workers to select from a NIOSH-approved list of N95 respirators "to help protect themselves from diseases potentially spread through the air, such as SARS or Tuberculosis." The list sorts thousands of models alphabetically by brand name and model and specifies which ones contain an exhalation valve. By Salon's count, CDC currently recommends 624 models of valved N95 respirators. For example, the list includes the kind of N95 respirators made by 3M and sold in hardware stores as dust masks. Of the 54 3M models that the CDC recommends to health care workers, after a review from NIOSH, 17 of these feature valves.

Likewise, an adjacent federal watchdog agency, the Occupational Health and Safety Administration (or OSHA, within the Department of Labor) recommends valved N95 masks to prevent against tuberculosis spread. In their own investigation into the question of inward mask leakage, they conclude, based on examinations by several investigators, that "the concern that the exhalation valve would permit inward leakage of air contaminates is unfounded. . . . The wearing of a valveless fabric type disposable respirator has no advantage over a respirator equipped with an exhalation valve." OSHA notes that of the studies that measured "leakage rate and/or aerosol penetration under dynamic test conditions," and which evaluated masks with exhalation valves, "The general conclusion was that for a properly maintained exhalation valve of an elastomeric facepiece respirator, the inward leakage of the exhalation valve is less than the allowable leakage of the high-efficiency particulate air (HEPA) filter (0.03%)," they write on their site.

Deconstructing malarkey around valved N95s

The CDC's the current recommendation regarding valves that regulate outward flow of air notwithstanding, the agency previously recognized the benefits to valves, stating, "An exhalation valve reduces excessive dampness and warmth in the mask from exhaled breath." Damp or wet masks are not merely uncomfortable, but they are dangerous — as they can increase the transmissibility of airborne viruses to the user.

Further, the CDC admits that N95 respirators (with or without valves) are safer than surgical masks when the user inhales:

"Surgical masks are not designed for use as particulate respirators and do not provide as much protection as an N-95 respirator. Most surgical masks do not effectively filter small particles from air and do not prevent leakage around the edge of the mask when the user inhales."

So what does the CDC have to say about loose-fitting masks, like surgical masks? Those would seem to leak some air around the edges upon exhalation, perhaps in a similar manner as a tight-fitting valved mask. The agency suggests that they are no safer regarding COVID-19 protection than valved N95 respirators when the wearer exhales: "Loose fitting masks and respirators and N95 respirators with exhalation valves might allow unfiltered air exhaled by the wearer to escape."

The operative word here is "might." Yet the CDC does not point to evidence to support this assertion, however commonsensical it may be, just as they offer no evidence to support their claim about valved respirators, nor comparative data regarding their effectiveness in slowing the spread of COVID-19.

Incongruously, the CDC guidance now suggests that a coarsely woven and loosely fitted bandanna or neck gaiter is somehow safer than one of the 624 valved N95 respirators that the CDC recommends to health care workers. What might fly in the industry-friendly, science-averse Trump CDC might be seen as malarkey in another administration.

The basic logical premise of the CDC's guidance is this:

  1. Valved masks allow exhaled breath into the atmosphere.
  2. Thus, if the wearer is infected, then their exhalations could infect others.
  3. Therefore, these masks should not be relied on for "source control" of the spread of the virus.

While there is a common sense to this, the CDC employs inaccurate and loaded language rather than science to make its point –– a point that is far broader than the facts will support.

Many valved masks, such as those made by Cambridge Mask and Vogmask, are designed to securely fit so there is no leakage of air coming in or going out. Air is filtered at N95 filtration or better going in (removing at least 95% of airborne particles), and is gently dispersed by the valve going out.

An example of the CDC's use of false and loaded language is its claim that valves "allow air to be exhaled through a hole in the material." (This claim also belies OSHA's study.) An actual valve is a secure plastic fixture with a membrane that opens when you breathe out and closes when you breathe in. It is not by any reasonable definition, a "hole."

The CDC also claims that potentially contaminated respiratory droplets are "expelled." This suggests an action of some force, which is a laughable misrepresentation of the way valves release exhaled air –– as anyone who has put their hand in front of a facemask valve can attest. Nevertheless, their broad conclusion is, "this type of mask does not prevent the person wearing the mask from transmitting COVID-19 to others."

This may certainly be so in settings where people sit closely together such as on trains, planes, buses and in such other indoor locations as theaters, churches, and schools –– particularly if people sitting next to you are not wearing a mask or wearing one that is loosely fitted or made of porous fabrics. (The CDC also sensibly advises health care workers elsewhere on its web site that a valved N95 mask is not appropriate in sterile medical situations, like "during an invasive procedure in an operating or procedure room.")

However, in most other situations, what breath emanates from the valve is diffused, indirect, and unpropelled into the air –– unlike talking, coughing, laughing, and singing without masks. Thus people nearby who are wearing masks are unlikely to become infected by the air emitted from mask valves, particularly outside, and particularly in the wind and sunlight. Sunlight contains UV radiation that damages or destroys COVID-19.

But if you don't already have a loosely fitting mask made of porous fabric (like a bandana or a tee-shirt) the CDC will show you an instructional video by Surgeon General Jerome Adams making one from a cleverly folded tee-shirt and two rubber bands. The CDC avers, however, that such masks should allow "for breathing without restriction." 

But valves are important for many people, in many circumstances, precisely because they make breathing easier. In fact, the lives of people who are at the highest risk of infection and death from COVID-19, due to age and/or underlying medical conditions, may depend on N95 respirators with exhalation valves. Many masks, and not just N95s, are hard to breathe through, particularly for long periods of time. The greater the fit and protective filtration, the harder it can be to breathe. We have seen check-out clerks behind plexiglass screens, sweating and suffering because their valveless medical-style mask is too much for sustained periods.

Two-way protection

Another red flag in the CDC guidance is that it suggests that masks are intended only to protect others, when in fact they protect in both directions. While their stated concern is "source control," the CDC has no warning against leaky unfitted masks, including those better-than-nothing cloth face coverings and other homemade masks of any quality. What's more, the CDC not only recommends them, but features the Surgeon General showing us how to make one. While these loose-fitting T-shirt DIY solutions may suffice in a pinch (until the uncomfortable rubber bands break), obviously they work poorly for the purpose of source control.

3M states: "Note that surgical masks, procedural masks and face coverings – which are often worn to control the spread of infectious diseases – are not designed to fit tightly to the face and have gaps around the face through which air will leak both inward when the wearer inhales and outward when the wearer exhales, potentially including expelled particles."

3M added that procedure masks and homemade cotton masks do not fully prevent the spread of virus particles either because in addition to gaps between the mask and face, "air and particles will also travel through the mask material at different rates depending on their construction."

So what could have propelled the CDC's recommendation to ditch valved masks?

It may have something to do with the Trump administration's accommodation of the airline industry, and the struggle of the airlines to cope with the pandemic.

The airline industry connection

On April 24, United became the first airline to require employees to wear masks. Three days later, based on the CDC's voluntary guidance to wear facemasks outside the house as a best practice, JetBlue announced that it would require passengers to wear masks, too, effective May 4, 2020. On April 30, Delta Airlines announced that passengers would be required to wear masks, also effective May 4. Frontier Airlines and Lufthansa announced the same day that they would require passengers to wear masks on planes and in terminals by May 8.

On July 27, Delta banned "any mask with an exhaust valve" on its flights, while allowing any basic "cloth face covering over their nose and mouth." This would include a neck gaiter or loosely woven, loosely fitted bandanna with gaps around the nose, beside the ears, and under the chin big enough to poke fingers through. A sleeping passenger with a cloth napkin over his face might arguably pass muster by Delta's standard.

After the CDC updated its guidance on valved masks on August 7, Delta claimed that it was "aligning with best practice guidelines from the CDC" – although Delta had actually banned valved masks nearly two weeks earlier. That suggests that the CDC was following Delta's lead. It may not be coincidental that both the CDC and Delta are headquartered in Atlanta.

Yet there were no industrywide standards or federal rules for what kinds of masks would suffice, and no federal requirements for people to wear masks in airport terminals. Airports set their own policies, in line with local and state laws, leading to a patchwork of rules that were difficult to understand or enforce. Of the 30 largest airport hubs, 20 required facemasks in July.

The airports, along with unions representing pilots and flight attendants, lobbied for a federal regulation requiring passengers to wear face coverings on planes and in terminals. But the airlines opposed getting the Federal Aviation Administration involved, arguing that no other industry was subject to such a nationwide rule. The airlines preferred to set their own policies. The unions countered that a uniform federal rule would be easier for employees to enforce.

"Lawmakers want a federal mandate and so do flight attendants," said Sara Nelson, president of the Association of Flight Attendants-CWA. "Just like anyone smoking on a plane faces federal charges and fines, so too should people understand the serious consequences of putting the health of others at risk by refusing to wear a mask."

The airlines won. And the airports, the unions, the public, and the reputation of the CDC lost.

It is understandable that airlines want to be able to better justify seating people like canned sardines again. (They make more money that way). The question here is not only the risk to passengers and crew, but also to what extent the CDC may have accommodated this industry at a time when it is pushing hard to "open" the economy.

The Hill reported on June 21 that airports had begged the Trump administration to set a facemask policy for passengers. Airports Council International–North America President Kevin M. Burke, whose group represents commercial airports, had testified at a hearing of the House Homeland Security Subcommittee on Transportation and Maritime Security. In his testimony, he argued that if all TSA and airline employees, and all air passengers, wore masks, then it would be easier to decrease social distancing requirements while increasing airline consumer confidence.

"I can't emphasize that enough," he told The Hill, "we would welcome regulations on a temporary basis that you should wear a mask in an airport when you're transferring through it." The airports and the unions not only did not get the regulation that they had fought for, but the CDC guidance on valved masks achieved a key aim for the industry without appearing to be just for them. The guidance is cast as a uniform standard to be applied throughout society.

Unfortunately, this is not the first time that government agencies and a compliant, conveyor-belt media have spread misinformation about masks in the name of (faulty) science.

Early in the pandemic, Americans were told not only that they don't need to wear masks, but that they don't work. It is possible that this was a lie intended to try to discourage consumers from buying up protective masks that were desperately needed by health workers, and were in short supply at the time.

But by lying and telling the public that they don't need masks, as University of North Carolina sociologist Zeynep Tufekci wrote in The New York Times, "the authorities sent a message that made them untrustworthy." CDC is repeating this error in issuing a broad recommendation about a narrow matter that requires a qualified view, one that would not merit bombastic headlines. And the CDC is repeating their error in scolding the public not to wear valved N95 respirators because they are allegedly dangerous, while recommending them to health care workers because they are safe.  

The subtle scapegoating of valved masks notwithstanding, the exponential spread of the coronavirus in 2020 is not due to the relatively small number of people wearing valved masks, but rather a major factor is the overwhelming number of people who refuse to wear masks of any kind, those who wear inadequate masks or who do not wear masks properly, and who do not socially distance and who engage in large group events without adequate or even any protection.

By Frederick Clarkson

Frederick Clarkson is a senior research analyst at Political Research Associates, a progressive think tank in Somerville, Massachusetts.

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By Jonathan Hutson

Jonathan Hutson is a researcher, writer and human rights advocate. He is the architect of the Satellite Sentinel Project, which George Clooney launched in 2010 to corroborate eyewitness reports of war crimes with satellite imagery and analysis together with open-source information. Hutson and his translator, Kibrom Goush Mouz of Khartoum, worked pro bono to interview eyewitnesses in four refugee camps in eastern Sudan in August-September 2021. A nonpartisan, nonprofit 501(c)(3) organization, Giving Back to Our Roots, paid their travel expenses. Maxar and the U.K.-based nonprofit Vigil Monitor provided satellite imagery and analysis.

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