Doctor demonstrates for dummies that even six masks don't lower oxygen intake

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So he’s a demonstrator?


Well, he’s not a dummy.


No, a pro-tester


we are witnessing a severe outbreak of chronic dickishness in this country


There are very obviously a huge number of people who are being complete morons about refusing to wear masks and giving absurd reasons for doing so. I haven’t been indoors anywhere but my or a family members’ home or car since the beginning of March, and am confident this is the right policy to continue following. But, making random videos that pretend to be strong counterarguments isn’t actually useful in changing what those people think. Nor is the constant storm of virtue signalling and weird shaming. Yes, we can sit still in a mask indefinitely without lowering out blood oxygen levels. This does not imply that the same holds true when exercising, or in hot or humid weather, or after multiple hours.

It also doesn’t address any of the purely mental effects of mask wearing. Feeling like your breathing is constrained, even if you’re getting enough oxygen, can cause anxiety and panic attacks, especially for people with relevant traumas in their past, of which I know several; for them wearing a mask for more than a few minutes can trigger PTSD symptoms, and the constant stream of “patriots wear masks” signs and getting yelled at by strangers when outside on a trail, in places where masks aren’t required and the risk of coronavirus transmission is essentially zero, doesn’t make things any better. I just wish people would try to understand what the mask-wearing rules are in different places and why they exist a little more precisely, and apply them with a little more compassion.


two things

  1. this is an absolute lie and incredibly stupid demo, masks most certainly lower oxygen intake


the trade off is trivial

but you don’t have to lie to people, sheesh

here, have an actual scientific study, they most certainly lower oxygen

you lose 5% with surgical mask and 10% with N95

but you also lose 100% if you are dead from Covld19

or have lifelong lung or heart damage or incurable chronic fatigue


I admire your impulse to compassion.

I would be interested to hear your estimate of the ratio between these people

and the people for whom

is true?


One of my masks is quite good, with 3 layers of tight-weave stiff cotton plus a pocket into which I put an additional filter layer.

When I go to the hospital (for other medical reasons) they automatically ask you to put a disposable paper medical mask over whatever you’re wearing. I have learned that this 5th layer is a layer too far for me. So now I know to wear any of my other masks when I go there, so that the additional layer can be tolerated.

At the hospital, by definition there is a higher percentage of people walking around with medical issues. I see a number of different types of the clear face shield that some people use when they can’t wear a mask. But, everyone is wearing something. Turns out, when you know you’re going to be around possibly infectious people, your ability to figure out how to ‘mask up’ increases greatly.


It’s a very good question. I honestly have no idea, both because my own social circle is not a random sampling and because most people in the latter group aren’t nearly as likely to be talking about it publicly.

The more frequent claim that I’ve been hearing from anti-maskers is that masks cause excessive recirculation of CO2, leading to hypercapnia. This is mostly, but not completely false. Depending on the type of mask and the duration of use, some amount of additional CO2 buildup above the baseline is to be expected. Most people have no issues tolerating it and the benefits far outweigh the risks, but I’m not sure that telling paranoid people that there’s absolutely zero effect on breathing at all is the best strategy to earn their trust because there are pre-existing studies that suggest otherwise.

If only there was some credible group of medical experts who had firsthand experience wearing face masks for multiple hours so they could let us know it was safe.


Intuitively, I do not understand how CO2 “builds up” inside a porous mask. There’s hardly any volume between your face and the mask, only a fraction of a human breath. So air is being transferred to and from that space to the air around you constantly, mixing with fresh air and diluting the CO2 you exhale. Sure, if you put a sensor between your face and the mask and measure CO2 buildup while exhaling shallowly (a tactic I’ve seen used to “demonstrate” how bad masks are) you’ll see increased CO2 levels. Then you continue breathing normally, and it dissipates. At least, I don’t see how it could be otherwise, just using basic fluid dynamics.


Yes, the volume between your face and the mask isn’t huge but it is something. And it’s that amount of volume that (at least partially) gets re-inhaled when you’re taking your next breath, so that portion of the incoming air would presumably have a little more CO2 than the surrounding air.

Look, I’m definitely not trying to defend anti-maskers or provide them with extra ammunition, but published studies conducted years ago did carefully measure this stuff and found a non-zero effect, at least with n95 masks. So we might as well recognize that reality as we make the argument that the benefits of mask wearing for everyone’s health far outweigh any risks.

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I understand there is an effect; I don’t think anyone advocating mask usage is saying that they have zero effect on the breathing of those who wear them. But not only is that effect negligible for the vast majority of people, but anti-maskers are using a temporary decrease in oxygen directly in front of their faces to justify not wearing them at all. That’s the problem. Not masks.


You all are missing something. This doctor looks relatively fit and in shape. The obesity rate in America is 40%. I’m guessing most of those people don’t exercise that much and can’t jog a mile without getting winded. I certainly include myself in that category. I’ve noticed as I have fallen out of shape my breathing is shallower and faster. As @spetrovits was asking, with a reduced lung fill and increased breathing rate the amount of CO2 you push through the mask becomes less. Essentially you are breathing more of your own air back in due to the faster shorter breaths.

I’m not saying any of this is a valid reason not to wear a mask. But I know if I put on my N95 and work in the yard there are times where I need to stop for a few mins and take some deep breaths. Typically I’m expending more energy doing actual work, but I understand where some of these people are coming from.

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True, you’re right about that. I have no medical experience whatsoever, but I’ve worn masks for extended periods myself in a lab/cleanroom setting and am aware that this is a perfectly reasonable thing to do. I was thinking about the “after multiple hours” thing as a kind of modifier to the previous items I listed, but didn’t actually write that.

Ok, then it sounds like we’re pretty much on the same page! But some people really do seem to be saying that the effect on breathing is literally zero, and the pedant in me just couldn’t let that go for some reason.

Here’s a thing I have discovered. I routinely double mask at the office. There is little more dead space, and a slight increase in work of breathing, but neither is terribly significant. 8-10 hours a day, no biggie. When I have to Dr a face shield (for aerosol-generating procedures) the additional dead space traps a boatload of extra CO2 and limits the amount of time I can spend “fully armored” to 10-15 min at a stretch. We do not have PAPR units, which would obviate that problem, so I just structure my timing carefully.