I just had to write a new version of this article: https://blog.adamgrant.me/of-course-masks-do-not-cut-off-oxygen-increase-co2/

A group of videos are making the rounds on social media using hazardous gas equipment to allegedly prove masks do more harm than good in the age of COVID-19. It's a neat parlor trick, but is it true?

We should first acknowledge these devices are designed to detect hazardous conditions in working environments. Instead, the conspiracy theorists are shoving the sensor into the confined space between their mask and their skin. These devices are also not designed to measure fleeting changes in gas concentrations as you'd expect in a small space where the mask wearer is breathing in and out.

In case you're still not convinced, here is a medical professional doing the same tests with multiple masks as well as measuring CO2 intake

No masks are not going to hurt you, obviously

The video was uploaded by Chuck Middleton, whose YouTube videos include eccentric armageddon themed christianity, moon landing denials, and 5G tower conspiracy theories, claims to use real, "OSHA approved" and calibrated equipment. This was enough for retweeters to accept the brief video as a scientific consensus.

At the end of the article, I break down why this test is misleading but first, let's hear from an actual surgeon.

The nice thing about science is a result needs to be independently reproducible, otherwise it's not reliable.

It turns out, plenty of medical professionals have already done exactly that.

Here are some more tests, all very reproducible. Big thanks to @NicoleB_MD for gathering volunteers.

Take a look below and ask yourself if you'll believe decades of empirical evidence and medical professionals or a conspiracy theory YouTuber.

But why does he get a different result?

I wouldn't be surprised if this instrument is real and calibrated just as the poster claims. However let's not confuse scientific equipment for actual science. Note the results from medical professionals above come over long periods of time. The poster takes his reading in an instant, complete with a scary sound inciting terror. Having more data is a good thing.

Next, let's review what the poster is actually measuring:

  1. Without the mask, the instrument measures the ambient air.
  2. With the mask, the instrument measures a small confined pocket of unmoving air by the corner of his mouth.

You won't be surprised to know that you don't rely on that small reserve of probably oxygen-poor air at the corner of your mouth when you breathe.

If you're like most people, you'll actually inhale, bringing in oxygen from in front of and around the mask.

But this is a real scientific instrument!

Let's not confuse scientific instruments for science. I researched the exact device the poster used in this video. It's not a medical device and it's actually designed to measure hazardous gases in a large space having nothing to do with medical industries.

According to the product manual for the IBRID MX6 Multi Gas Monitor,

"Sudden changes in atmospheric pressure may cause temporary fluctuations in the oxygen reading."

That's because it's designed to be used in a large space, not confined between a mask and someone's skin, where pressure will change with breathing.

The device has special manuals for the mining industry, refuge chambers, and mechanical pumps.

It cannot be overstated, this is the wrong device for the job. But just in case you're not convinced, even the company that makes this product agrees their product should not be used in this way.

Pulse oximeter

The device used by medical professionals in this post is exactly designed for what the conspiracy theorist was trying to measure. So why use an instrument for mining when your local pharmacy sells these devices for $20-50?

According to the American Lung Association, "If you have a symptom of shortness of breath or a known lung or heart condition, your doctor may use a pulse oximeter. The pulse oximeter, or Pulse Ox, is an electronic device that measures the saturation of oxygen carried in your red blood cells. Pulse oximeters can be attached to your fingers, forehead, nose, foot, ears or toes. The device may then be reused or disposed of...

The pulse oximeter, for example, a finger probe, uses a cold light source that shines a light through the fingertip, making the tip appear to be red. By analyzing the light from the light source that passes through the finger, the device is able to determine the percentage of oxygen in the red blood cell."

What does hypoxia actually look like?

The video claims the oxygen under the mask was so low as to be occuptionally dangerous. It turns out we know what hypoxia looks like and this effect has been thoroughly studied by the military.

Check out the middle of this video where we see a pilot wear a pulse oximeter while trying to put shapes into corresponding holes while naming them. eventually his brain function is so compromised he is unable to put on his own oxygen mask, already partially strapped to his face, knowing he could suddenly die should he drop just one more percentage point in O2 saturation.

Also note this instrument has a 1% margin of error. Do not try this at home!