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September 29, 2020

Droplets and Aerosols, Why Catching the Sneeze Doesn't Reduce Viral Transmission

(Part 2 of Face Masks: A Placebo with Harmful Side Effects)

(This is the second article in a series exploring the science, psychology, and unintended consequences of COVID-19 face masks.) 

Part 2 - Droplets and Aerosols, Why Catching the Sneeze Doesn't Reduce Viral Transmission

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In part 1 of this five-part series about face masks, I discussed how the politicization of the COVID-19 virus has led our health authorities to prioritize opinions over evidence, causing them to turn their backs on decades worth of randomized controlled trials, which clearly demonstrated that face masks are not an effective tool to reduce the spread of respiratory viruses. 

In this article I will explain why they don't work, despite our initial gut instinct that they should.

Let’s begin by looking at the COVID-19 virus particle itself, which has an approximate diameter of 0.12 microns. For context, that's between 5 and 50 times smaller than a bacteria, between 30 and 1000 times smaller than a mold spore, and between 150 and 2000 times smaller than a grain of pollen. Thus, a virus particle not contained inside a droplet or aerosol presents an impossible challenge for a face mask.

Even an N-95 respirator is only able to effectively filter particles down to approximately 0.3 microns. And only when that N95 mask has a perfect seal against the face to prevent your breath from bypassing the mask altogether. An N95 mask can catch individual bacteria, mold spores, and pollen, but not viruses. Viruses, on their own, are just too small. It's like putting up a chain link fence to stop a mosquito. If the pores in a mask were small enough to stop a virus, you couldn't breath through it.

However, most of the time the virus is not floating around in the air on its own. Instead, it is contained in tiny droplets or liquid aerosols (composed of snot, mucous, or water vapor). If those droplets are big enough, they will be filtered by the mask (catch the sneeze). That is the theory behind why masks are being promoted as an effective tool to protect other people from your virus, but not to protect you from other people's virus. It's an implicit acknowledgement that aerosol virus particles are small enough to be suspended in the air and will go straight through any mask that you wear, but that gobs of virus-laden snot released by a sneeze or big drops launched by a cough will be caught inside the mask instead of coating every surface that they reach. 

Theory is neat and tidy until it runs into reality. If big drops were involved in virus transmission, infection rates would be noticeably reduced when everyone wears masks. But the outcome of all the randomized controlled trials mentioned in part 1 of this article demonstrates that this theory about big droplets meaningfully contributing to viral transmission is simply wrong.

350 years of medical research separate the masks in these two images, yet when we panic, we still take refuge behind a false sense of security that fails to address the actual mechanism of disease transmission. Left: Personal Protective Equipment in 1656. Right: Personal Protective Equipment in 2020. Image Credits: Gerhard Altzenbach / Public domainPooja Jadhav / CC BY-SA (

At first glace this seems counter-intuitive because we know that snot and phlegm is absolutely full of virus particles. But once we zoom in on how the droplets and aerosols behave, the mystery is quickly solved.

Thanks to gravity, droplets larger than 5 microns quickly settle to the ground. Coughing produces droplets that average around 8.35 microns, whereas sneezing produces droplets between 0.5 and 12 microns. "Despite the variety in drop size, large droplets comprise most of the total volume of expelled respiratory droplets.In other words, droplets large enough to be caught by a mask are also large enough that they are not getting inhaled into your airways. Gravity is already doing the job of protecting us from the big drops; the mask is redundant. Getting splashed by a large droplet from a cough or sneeze isn't going to infect you unless you wipe that droplet off your face and then pick your nose with the same finger without washing it first. Respiratory viruses do not infect us through our skin; they must enter our respiratory tract. That's why frequent hand washing works, but masks don't. That’s why you don't need someone else to wear a mask to protect you from their coughs and sneezes. Wash your fingers. Your safety is literally in your own hands.

However, coughing and sneezing aren't the only way to produce droplets. Normal breathing (also called tidal breathing) and breathing with congested airways (which cause a film of mucous to temporarily restrict airflow before bursting like the membrane of a bubble) both produce much smaller droplets, which we collectively call aerosols. Normal breathing produces aerosol droplets averaging around 0.07 microns. And breathing with congested airways produces aerosol droplets between 0.2 and 0.5 microns

These small aerosol droplets also contain virus particles. And these aerosols will remain airborne for a long time, allowing them to be inhaled by other people. These are the culprits doing the dirty work of spreading the virus. 

That's why cloth face masks are useless against a respiratory virus. They can't stop aerosols. Neither can surgical masks. N95 masks will only stop the largest of these aerosol droplets (not the smaller ones below 0.3 microns) and only if the N95 mask forms a perfect seal against the face. Anything less than a perfect seal will cause the air to take the path of least resistance around the outside of the mask as you exhale. Face masks simply aren't up to the task of stopping this enemy.

And let's stop pretending that electrostatic forces are capable of filtering these microscopic aerosol particles. If they did, we would have seen some reduction in virus transmission rates during the previously mentioned randomized controlled trials. That's the point of randomized controlled trials, they allow us to test theory in the real world. If the trials show no difference, the theory, however neat it may be, is wrong.

But for those of us who prefer a more visual demonstration of the ineffectiveness of filtering aerosols, check out the two videos below of e-cigarette steam penetrating through face masks and swirling around all the unsealed edges (steam has an approximate particle diameter of 15 microns). 

Dr. Theodore Noel's video (you can see more of his videos on his YouTube channel here): 

And this short video from Tony Heller's YouTube channel:

In short, face masks are a useless tool for stopping an aerosol-transported respiratory virus. Those aerosols are filling the air space all around you, whether you wear a face mask or not. All masks do is provide an illusion of safety, a placebo to make you feel safer, a comforting symbol that disguises the fact that our politicians and health authorities are utterly ignoring everything we know about how this virus is actually transmitted. They are a sugar pill that you can wear on your face. 

Ironically, we should be thankful that masks don't work because if they did, they would be dangerous to anyone wearing them while shedding the virus. If they worked, the virus particles exhaled by your breath would be trapped inside your mask. On your next inhale, all those virus particles would be sucked deep down into your own lungs into regions not already infected. What may have started as an upper airway infection would thus spread deep into both sides of your lungs. 

Furthermore, there is a concept in medicine called viral load, which simply means that a small number of viral particles is much easier for the immune system to fight than a large dose, which can quickly overwhelm the immune system. If masks worked, rebreathing your own viral particles would cause you to increase your own viral load. Thus, if masks worked, mask wearers would have more serious COVID-19 infections than those who don't wear masks.

As with so many things in life, what seems obvious at first glance is rarely what it seems once we dig into the nuanced details. When it comes to respiratory virus infections, our face masks are truly as ineffective as the beak-like masks worn by the plague doctors of the 17th century. And if masks actually worked, they would be as unhealthy for the patient as a medieval bloodletting.

So far, I've only covered the lack of mask effectiveness. But mask advocates often argue that even if just a single extra life is saved, mask recommendations would still be worth it. Their fanciful argument rests on the false assumption that there are no downsides beyond the inconvenience of mask wearing. That's simply not true. The most obvious harm caused by face masks is the topic of part 3 of this article series, the thousands of unnecessary deaths in our long-term care homes, which were directly (and needlessly) caused by dangerous policies guided by our misplaced faith in our ability to trap the virus with masks and filters. 

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Part 2 - Droplets and Aerosols, Why Catching the Sneeze Doesn't Reduce Viral Transmission


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  1. Very good article

  2. Hi Julius, can you point out the section of that talks about congested breathing producing droplets between 0.2 and 0.5 microns? I ask because I'm interested in data related to the claim that respiration expels large droplets only, and the virus-laden aerosols form outside the human body as water evaporates from the expelled large droplets. For example, here's what the CDC says currently (, accessed June 21st, 2021):

    People release respiratory fluids during exhalation (e.g., quiet breathing, speaking, singing, exercise, coughing, sneezing) in the form of droplets across a spectrum of sizes.1-9 These droplets carry virus and transmit infection.

    * The largest droplets settle out of the air rapidly, within seconds to minutes.
    * The smallest very fine droplets, and aerosol particles formed when these fine droplets rapidly dry, are small enough that they can remain suspended in the air for minutes to hours.

    1. I seem to have accidentally linked to the wrong artilces for the "0.07" and the "0.2 to 0.5" for you. I have changed the links.

      I seem to remember there was another article that I can't find at the moment discussing the "0.2 to 0.5" range and how the film of mucus that covers the airway momentarily closes it off and then bursts, thus producing the small aerosol droplets. If I can track it down in my sea of bookmarks, I'll let you know.

  3. I read an interesting speculation that what may happen with droplets is they collect on the mask, only to evaporate and be breathed out as aerosols later. I'd be interested in your thoughts on that if you have time to comment?


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