Previous: Dangerous Soaps: How Animals Use Surfactants
Next: Bird Eggs Warn Each Other About Danger



View count:368,466
Last sync:2020-11-23 22:45
On today’s SciShow News, we take a look at what that neck gaiter study is really all about, and also have a bit of good news about soot free flames called blue whirls.

Hosted by: Hank Green

COVID-19 playlist:

SciShow has a spinoff podcast! It's called SciShow Tangents. Check it out at
Support SciShow by becoming a patron on Patreon:
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever:

Bd_Tmprd, Jeffrey Mckishen, James Knight, Christoph Schwanke, Jacob, Matt Curls, Sam Buck, Christopher R Boucher, Eric Jensen, Lehel Kovacs, Adam Brainard, Greg, Sam Lutfi, Piya Shedden, Katie Marie Magnone, Scott Satovsky Jr, Charles Southerland, Charles george, Alex Hackman, Chris Peters, Kevin Bealer
Looking for SciShow elsewhere on the internet?
Neck gaiters

Blue whirl
2016 blue whirl:
2020 blue whirl:
Pollution, soot, asthma:
Environmental soot and inflammatory pathways:
UMaryland Press Release, Blue Whirl:
Diffusion flames:
Premixed flames:

Image Sources:
This episode was filmed on August 18th, 2020.

For up-to-date information on the COVID-19 pandemic, check out our playlist linked in the description. [♪ INTRO]. A recent study from Duke University has been making the rounds on news websites and social media.

The headline: neck gaiters — those neck wraps you pull over your face — are worse at preventing the spread of COVID-19 than wearing no mask at all. That is not really what the study shows -- nor was it meant to. It was meant to help other researchers learn critical information that we need to fight the pandemic -- not tell the public what to wear.

Pulling back from the reporting, this research, published in Science Advances, was basically a proposal for cheaply and easily testing the efficacy of all the different styles of masks that people have been wearing. The researchers built a device that used a laser beam and a lens to create a sheet of light inside a box to visualize human spit droplets. They had a participant repeat the phrase “stay healthy, people” into the box a few times, first without a mask as a control, then through a bunch of different styles of face covering.

The light illuminated the droplets as bright green blips, which they captured with a cell phone camera and analyzed with a computer algorithm that counted the droplets. Not counting the phone and the computational resources, the whole setup came in around two hundred US dollars. They looked at fourteen styles of face coverings, from a small square of cloth to properly fitted N95 respirators.

Then they gave each mask a relative score based on the unmasked control. So the unmasked trial got a score of one hundred percent, because a hundred percent of droplets got through, while N95s without valves scored less than one tenth of a percent. Somehow, the neck gaiter scored higher than the unmasked controls at 110%.

That's where the headlines that neck gaiters are worse than nothing are coming from: they saw more droplets with the gaiter. The researchers measured fewer large droplets and more small droplets in the gaiter trials, making them think that the gaiter split the bigger droplets apart. Which, if true, would make the use of them counterproductive, because those smaller droplets could hang in the air for longer.

But that is as far as their data goes. Only one participant tried out every combination of mask, and only three more tried out a couple other styles. Four people is an extremely small sample size, and their novel measurement device wasn't positioned exactly the same way for each participant or trial.

And their camera was a regular ol' 1080p mobile phone camera from 2018. While that's not bad for recording a TikTok, it wasn't powerful enough to detect droplets smaller than 120 microns, which make up the majority of droplets that actually come out of your mouth. So any patterns in the data are what we would call “preliminary.” The researchers were perfectly well aware of this.

They were developing a new experimental protocol. They used a small sample size, and knew that they would get underpowered results. Their goal was to test this new laser box device, and along the way they happened to notice the quirk with the neck gaiters.

That's why those headlines are misleading. The study showed a preliminary bit of evidence that's worth investigating further, but what's been reported as a definitive result is more of an opening for a new line of inquiry. So no, they don't prove that neck gaiters are worse than wearing no mask at all.

But they did give us a way to learn more about whether that might be the case. If you're looking for some good news, researchers from the. University of Maryland have found a way to make a flame that doesn't leave behind any soot.

Soot contributes to climate change and acid rain, as well as tons of health problems in humans, so reducing it is probably a good idea. The research was inspired by fire whirls, which, yes, are a real thing, not a made up Pokemon attack. These things can show up during intense wildfires when the wind hit the fire and terrain just right, creating a frankly terrifying vortex of flames.

In 2016, researchers were studying whether these fire whirls could be used to clean up oil spills over water. Unexpectedly, the swirling yellow flame turned into a beautiful blue flame they dubbed a blue whirl. They noticed that this spinning blue whirl left behind barely any soot.

Which led them to consider whether they could get flames to burn this way on purpose. Now it's really difficult to learn that kind of information from just recreating and observing blue whirls, so this research used simulations to visualize how the flame formed. In particular, they were interested in how the flame uses fuel and oxygen.

You need both to make fire, but they can come in different structures. In some flames, the fuel and oxidizing agent are already mixed together — what's called a premixed flame. Other times, you get a diffusion flame, where the fuel and oxygen are initially separate, but mix by diffusion.

But it wasn't an either/or situation for the blue whirl. It was all of the above. One area of the whirl was a diffusion flame while others were premixed, and that bright ring in the middle is where they met.

That gave the researchers some insights into how a fire whirl might become a blue whirl. There are still unanswered questions. Like, is it possible to skip the fire whirl stage and make blue whirls by themselves?

And they don't yet know how to actually use what they've learned, say, in a car engine or power plant -- but if they could, it might lead to reductions in soot pollution. Both of these stories show why science is never one and done. We'll keep learning about this stuff -- and the answers will create yet more questions.

Thank you as always for asking, and thanks to our patrons for helping us explain the answers -- especially this month's President of Space, Matthew Brant! Your continued support means a lot to us, so thank you! If you're not a member of our community of supporters, and you'd like to be, check out [♪ OUTRO].