The question of whether masks work has been debated since the first documented COVID-19 cases arrived in the United States earlier this year. A wide range of theories and statements on the subject continue to make rounds on social media, and hundreds of sources attempt to explain their views with various kinds of data. Some of these sources claim to be grounded in science, some in common sense, and some in the idea that anything having to do with the virus is politically suspect.
Amid the symphony of arguments, conversations on the topic can often get heated. From the myriad of sources claiming to have answers, online commenters and posters provide articles that defend each side’s respective positions.
Some skeptics ask questions like, “If you are wearing a mask, then why worry about what I am doing?” Others wonder, “if it doesn’t help me, how is it helping other people?” Many mask-doubters point out that as much as 70 percent of people infected with COVID-19 were wearing masks when they picked up the virus. The firmest doubters call masking recommendations a “guilt tactic” to coerce people into wearing a mask when they don’t really need or want to.
Pro-masking sources often explain that masking does not protect the wearer from the virus so much as it protects others from the wearer. Although some vocal exceptions have gained traction, a significant majority of health professionals at all levels support the idea that with respect to COVID-19, masks primarily protect others from the wearer. For that reason, they endorse masking as an effective measure to reduce the spread of the pandemic.
At the core of many anti-mask arguments is the simple fact that the virus itself is a microscopic particle that is smaller than the pores in most cloth or paper masks. Because of this fact, many doubters assume that the virus will get through, and that there is therefore no point in wearing a face covering at all. They’re not entirely wrong. The virus is smaller than many masks’ pores or meshes, and sometimes the virus does get through masks.
Compounding this assumption is the fact that many pro-mask sources don’t really address how masks keep the majority of viral particles contained—which they do. Many pro-mask memes and articles making the rounds, perhaps even the majority, fail to adequately explain the mechanics of how particles do or don’t get through a mask, and what circumstances make them effective.
A key to how masks stop the virus is moisture. Anyone who has ever clapped two chalkboard erasers together, or perhaps a pair of dry, dusty boots, knows that doing so causes a cloud of dust to quickly fill the air. If the air is still, the cloud lingers for some time before it dissipates. What anti-maskers know is that if a person were to put on a surgical or cloth mask and walk into that cloud, they would very likely get a nose full of dust. The same thing would happen if a person were to walk through the invisible cloud that hangs in the air after a COVID-infected person speaks or exhales.
However, that dust cloud is generally going to be extremely dry, and it is not typically going to be moving with any kind of force. Those two factors make a key difference.
When a person exhales, the wind that passes forth from their nose or mouth has force and direction. It also contains a great deal of moisture. When a mask-wearer exhales, they are forcing their damp, maybe virus-laden breath into the fabric of their mask.
The naked eye can’t see that moisture, but it’s there. The moisture in a person’s exhale is most often visible when it is chilly out, in which case the warm vapor briefly appears as a white cloud before it cools down to the ambient temperature. The rest of the time, the clearest evidence of the moisture on a person’s breath is the tiny bit of water that can accumulate on an object held up next to the nose or mouth.
In fact, anyone who has been wearing a mask during the pandemic might have noticed damp spots wherever they exhale into the cloth or paper. That moisture is evidence that the mask is doing its primary job as it relates to COVID-19: catching stuff on its way out of the respiratory system.
Those who point out that masks must not work because the virus is small enough to pass through many materials are partly right. The virus is, indeed, that small. However, there’s something important to know about tiny particles and moisture: they stick to one another. This is a key point that is often not mentioned in articles that explain the relationship between viruses and water vapor particles.
However, because of this, tiny droplets of water tend to pick up particles they come into contact with, which they are constantly doing in a persons lungs where the turmoil of inhalation and exhalation forces them together. This helps the virus, since like people and most other living things, the virus is an organism that needs water to survive. Therefore, if a person carrying the virus exhales, the tiny, individual virus organisms are carried in the not-as-tiny but still microscopic water droplets that form the humid vapor in a person’s breath.
This same principle applies in industrial air purification systems. In some mills, factories, and other environments that produce airborne dust, there are systems available to increase the presence of humidity or water vapor in the air. The microscopic water particles pick up the microscopic dust particles, which then settle out of the air more easily or are more easily picked up in air filtration systems.
Many of the water vapor particles in a person’s breath are bigger than the pores in the paper or cloth that most masks are made from, and so they get caught in the material. Even the vapor particles that are not so big stand a decent chance of getting caught in the material, because it is porous, and porous materials catch moisture very easily. Even non-porous materials show a difference – if sand strikes a piece of glass, none but the tiniest particles stick, but if water strikes the same piece of glass, a noticeable number of droplets will be left behind. Just as it catches and captures particles, water also adheres to a wide range of surfaces.
Your exhalation is gently pushing whatever is in your breath through your mask, and your mask is then catching a significant portion of the material your breath is carrying, aided by the moisture in every bit of air you exhale. The virus can still get out if it makes it through the pores in the mask or in openings around the edges, but the overwhelming majority of it doesn’t.
If a chalk dust cloud were forced past a filter accompanied by steam, the same thing would happen. The filter would catch more of the dust than it would if there were no moisture present, because the steam particles would pick up chalk dust particles, and the filter would do a more thorough job of catching both.
There is one other important physical factor in how masks work. A mask provides the wearer less protection from inhaled particles than it does for other people from exhaled particles. When a substance is ejected from a hose, as long as there is not a spray nozzle preventing it, the substance travels in a more or less straight stream for a little while before resistance from the air causes it to dissipate into a cloud or to scatter. This is because the hose and nozzle impart force and direction to the substance being expelled, much like the barrel of a gun does with a bullet.
When a person exhales into a mask, their nose and mouth are like the hose, more or less shooting their breath directly at the fabric. This causes some of it to scatter, and some escapes around the edges, but the majority of the droplets and particles get caught up in the mask material first.
On the other hand, when a vacuum nozzle draws in a substance or particles, it draws from all directions around the opening. Unless a tube or other enclosure is present to direct it, a forced vacuum becomes quickly more non-directional with increasing distance from the source of power creating the vacuum. Even if a hose is present, that non-directionality applies just outside its entrance. Thus, the stuff being drawn in by the vacuum isn’t inside the hose when it starts moving, so the only direction it goes is toward the nozzle, whatever direction that may be.
When a person inhales through a mask, the vaccum created inside the tiny fabric draws all available air, which comes in through both the mask fabric and the openings around the side. It’s less likely to get the benefit of the filter, and since the largest virus-bearing droplets have likely settled from the air, the smaller ones, as well as any virus particles that might be temporarily outside of any droplets, might still make it through.
Due to these phenomena, the mask protects others from the wearer far more effectively than it protects the wearer from others. Exhalation without a mask produces a cloud of potentially virus-bearing vapor somewhat akin to the chalk dust cloud. Since many people can carry the virus without showing symptoms, this means that a non-mask-wearer can be infecting masked people with the airborne disease without knowing it.
Some who oppose masking also question whether the practice is safe from a sanitary perspective. Most reasonable mask proponents argue in favor of frequent mask changes, keeping reusable masks properly laundered, and other sanitary measures to ensure microbial growth does not become a problem. Because the moisture on a person’s breath, and the particles it contains, dissipate quickly outdoors, most mask proponents do not believe it is necessary to wear one when outdoors and away from other people.
Since people who wear masks or other face coverings for a living often wear them for extended periods of time, many engage in their own proper, regular cleaning and changing. The majority of professionals who have, for many years, worn masks regularly and for long periods on the job do so without adverse health impacts.
Even if some people are at risk of, for example, skin sensitivities, most mask proponents say wearing a mask for a normal grocery shopping trip or other errand should not present serious challenges for most wearers.
For those who must wear one for longer periods at work, precautions like cleaning, changing, and taking breaks outside and away from other people can ensure the safety of the practice of mask-wearing.
While many citizens may find reasons not to mistrust many authority figures, be they politicians or appointed, high-government medical professionals, a stance in support of masking is generally based on the simple physical principles at work here.
As health professionals like the staff at the Branch-Hillsdale-St. Joseph Community Health Agency and other organizations have said, masking helps significantly to prevent the spread of a disease that is harmless for a fair number, debilitating for others, and deadly for some. Until a viable vaccine is in widespread use, masking will continue to be a significant determining factor in how fast COVID-19 spreads.
This article has been updated since it was first published to include inline links to source materials. It has also had language added to compare similarities between the physical principles described and those found in industrial and firearms applications.
Dave Vago is a writer and columnist for Watershed Voice. A Philadelphia native with roots in Three Rivers, Vago is a planning consultant to history and community development organizations and is the former Executive Director of the Three Rivers DDA/Main Street program. Specifically as it relates to this article, his background includes more than a decade of experience as an educator and exhibit designer at museums and parks dealing in science, technology, history, and natural resources.