April 05, 2021

Is Outside Air COVID Safe? Are Masks Needed Outdoors?

When I visit parks in Seattle and the region, bike along the Burke Gilman Trail, cross-country ski at WA snowparks, or go hiking in the Cascades, I note that many people are wearing masks outdoors to avoid COVID-19.  A lot of people.

Some folks are clearly afraid and fearful of COVID exposure outdoors.  For example, I often see individuals making a point to avoid unmasked bikers or joggers on the Burke-Gilman trail...moving 5-10 feet off the trail and sometimes turning away. Occasionally it gets tense, as when one local scientist (not me) was angrily called a "Republican" when he was walking in a park without a mask.  

The fear of outdoor spread even hit the management of Seattle Parks last year, when several parks and their parking lots were closed because of COVID fears.

Photo by Nate Loper Through a Creative Commons License

It is time to bring science to this issue and to relieve the worries of many who wish to enjoy outdoor recreation.

In this blog, I will tell you about measurements of carbon dioxide (CO2) I took around Seattle this weekend, measurements that suggest little threat of COVID transmission outdoors. I will also review some of the latest scientific literature, which again does not indicate a significant threat of COVID transmission in the outside air.

The message of this information is obvious: wearing masks outdoors does not appear to be necessary.

My Field Experiment Around Seattle

    In my experiment, I used a sensitive CO2 sensor that makes use of proven measurement technology (see below).  Human breathing puts out a lot of CO2, roughly 4 percent by volume or roughly 40,000 parts per million (ppm).  The background level of CO2 in the free atmosphere is currently approximately 415 ppm.... a concentration much, much less than coming out of our mouths.

Thus, CO2 can act as a tracer of the air coming out of our respiratory systems, something mosquitoes know all about since they use the plume of CO2 we exhale to find us.  By measuring CO2 levels, it is possible to determine the relative concentration of air coming from humans and the degree of dilution by the surrounding air.

There have been a number of peer-reviewed scientific papers that have shown that CO2 concentrations are a potent tool for evaluating the potential for disease spread by viruses and other agents, with higher concentrations of CO2 associated with more transmission of disease (some examples of relevant scientific papers found here and here).  

Most of these papers use CO2 to measure the potential for transmission in indoor spaces, so why not take it one step further and evaluate potential disease transmission in the outside environment? That is what I did around Seattle on Saturday, a very nice day (high around 63F) with lots of people in the parks and outdoor locations.

My CO2 unit reported about 400-405 ppm away from roads and people, and this value represents the background level of carbon dioxide.

The Burke-Gilman Trail

My first stop was the crowded Burke Gilman trail, with folks walking, running, and whizzing by continuously.  There was no increase in CO2 concentrations compared to the background at any time (around 400).  Clearly, the diffusion/dispersion/dilution of CO2 by outside environmental air was very large.  And the same would be true of any COVID virus breathed out by anyone on the trail.

Magnuson Park

I then traveled to Magnuson Park, one of the most popular parks in Seattle.  First, I walked about a half-mile, back and forth, on a crowded path.  No increase in CO2 values above background (still around 400 ppm).  

Then I decided to really push things and walked around crowded picnic shelters, some with as many as 15-20 peoples without masks. (I suspect they thought I was being a bit odd as I circled around the groups, but this was for science!)   I could find no enhancement of CO2 above the background levels....natural movement of air diffused their CO2 emissions completely.    I did find a weak signal downstream of a raging barbecue fire...but even that was muted (about a 10 ppm increase 40 feet downwind).

So the bottom line so far:  natural ventilation and mixing in the outside air was effective in diffusing the CO2 emitted by people in an outside park environment, even when there was a high density of people.  And if CO2 enhancement by all the people was undetectable, the same would be true of COVID-19 virus emission by any infected individuals.  Parks appear to be entirely safe locations and masks are not necessary.

University Village Shopping Center:  Outside and Inside

Next, I went to the University Village shopping center.  There is a nice little urban park adjacent to the Apple Store.  It was packed with people enjoying the nice weather.  If there was going to be a place where human CO2 would be evident, this would be it, particularly with nearby structures lessening the wind flow.


I walked all around the park, even close to groups of people.  Only background levels of CO2 were observed.  No hint of people's CO2.  Atmospheric mixing was still large, and thus there was little threat of catching COVID-19 from the general environment.  And I found similar results near lines of individuals waiting to enter some U. Village stores.

Supermarkets and Indoor Restaurants

As a little side test, I then went into a busy local supermarket.  The CO2 concentration zoomed up to 830 ppm.  A warning, perhaps, about food stores.  

Then I went into a restaurant, one that was well ventilated (I could feel the breeze) and with reasonable spacing between tables.   The CO2 level was a very modest 520.  Turns out the restaurant had a CO2 meter, which read 530.   Good confirmation of my calibration and a positive note about the restaurant providing a safe environment for its patrons.

A Visit to A Gym

Then I stopped in a local gym, a major one located in northeast Seattle.  Lots of ventilation and the CO2 level was a very modest 465.   A safe place for one's workout and less than the value in my home (which is about 530).   People are required to wear masks in the gym, but quite honestly they probably aren't needed.

Reality Check

I shared my results with some local air quality experts and a well-known epidemiologist.  They thought my results were reasonable and not surprising.   They acknowledged that COVID transmission is far less problematic outdoors.  

One suggested that the risk outside was not zero:  imagine if you had a conversation with a highly infectious individual for an extended time at close proximity (within a foot or two), with little wind and the person was upstream of you.  Perhaps.  But you can imagine how unlikely this situation would be.  And easily avoided.


The epidemiologist, although generally agreeing about the safety of outdoor air, suggested the potential for a very short (transient) exposure to the long-distance breath of a COVID-infected person.

He noted the example of smelling cigar or pot smoke at a distance--might one get exposed to COVID the same way?  I suspect this is highly unlikely. First, large virus-containing droplets tend to fall out close to the infected (that is why there is a six-foot "rule" for separation).  And smaller particles tend to get diluted with distance. But just as important is that current best science suggests that extended or prolonged exposure to a COVID-infected individual is necessary, with the Centers for Disease Control indicating 30 minutes or longer (see here).  That is simply not going to happen outside if you and the source are moving around.


This never made any sense and prevent people from enjoying a healthful environment

Finally, what does the current scientific literature indicate about outdoor transmission?  The scientific literature is very thin on this topic, but here are some examples:

  • Qian et al., 2020:   Examined 1245 confirmed cases in 120 cities in China and identified only a single outbreak in an outdoor environment, which involved two cases. 
  • Nishiura et al., 2020:  Transmission of COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment (95% confidence interval). (they could not exclude the possibility that the few "outdoor" transmission might have occurred by undocumented indoor transmission)
  • Bulfone et al., 2021:  A review of all the literature on outdoor transmission.  They found only five studies, two of which are above.  They noted the poor quality and inconsistent approaches of most of the studies so far.

Quite honestly, one can only be disappointed in the quality of the "studies"  on outdoor transmission, which is surprising at this point in time.  Importantly, there is no compelling published research that demonstrates significant outdoor transmission.  

The Key Message

My observations of CO2 concentrations suggest that the diffusion, dilution, and dispersion of human exhalations are very large outdoors, making the threat of outdoor COVID-19 transmission very, very low.  This is consistent with the (limited) scientific literature on the topic.

Outside air is very safe, and it gets even safer during the summer since ultraviolet radiation rapidly kills airborne virus.  The logical conclusion from these results is that wearing a mask outdoors is probably unnecessary. Closing outdoor parks makes no sense at all.

If any of you see some weaknesses in the above logic, let me know.  That is how science works.
____________________________________________________________________
Public Radio Station KNKX and Cancel Culture
:  What Happens When a Public Radio Station Rejects Viewpoint Diversity and Goes Political.

107 comments:

  1. Those of us trained in atmospheric transport and diffusion have thought this way all along. Nevertheless I mask outdoors, a little 'political meteorology'.

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    1. Mayhaps you should abandon your 'political meteorology'... to show strength & not kowtow to political bullying & fear mongering Jimijr !

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    2. The virus itself has no political affiliation and does not care about shows of strength. I don't wear a mask outdoors unless I come into close proximity (say around 50')with people, because they on the other hand DO have political ideologies that include such dumb ideas as "showing strength" and have demonstrated that they will go to great lengths to prove it by purposefully disregarding distancing and even purposefully coughing in other people's faces to prove that how strong they are (the very definition of bullying.)

      My political meteorology is basically that a mask is a visual cue to folks that believe like you to bugger off.

      While Cliff can account for science he can't account for human nature. And while he mentions that "transient" air, I don't think he accounted for a full on sneezes and coughs or large crowds like full stadiums.

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    3. If someone intentionally coughs on you, that is called assault. I have never heard of this ever happening, let alone it being a somewhat common occurrence as you've implied.

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  2. Thank you for the sanity check.

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  3. Well written article supporting what I've believed for that past year. Thank you!

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    1. YESSS !! - Cliff is ... once again ... SPOT ON !! πŸ‘

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  4. The science makes sense, but mostly what the Covid mandates and protocols are about are liability/culpability along with not having to require complicated rules for EVERY situation. Even in rugged individualist libertarian Texas, stores are still requiring patrons to mask up. Mainly because there are no protections in place to absolve businesses in the event of a lawsuit filed by a patron who got sick or infected others.
    Really, all of this has been individual choice. There are plenty of examples where masks are not needed and yet have been worn while there are many more examples of where they should have been but individuals refused along with no enforcement. Which is understandable.

    Using Texas as an example again, they rely on a workforce of mostly younger, minimum wage retail employees to enforce masks in their work place, which really sucks for them. It is after all...Texas... and by nature many Texans are going to have a chip on their shoulder about it, and are ready to back their beliefs up with force in many cases. The 18 year old barista probably doesn't want a scene that could escalate into deadly violence for $7.25 an hour.

    End of the day though, it is still just a mask that unfortunately our country...since we are basically bat crap crazy by global standards, make a huge political stink about a simple piece of cloth. At least wear the thing in crowds, but many don't even do that. Maybe when we get past the basic common sense of where we should still mask up we can argue about the minutiae of where we really shouldn't.

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    1. I Live in Texas and no, they aren't. Store employee's are but Texas is 100% open and no mask mandate. It's personal preference of the org to choose to require it and most ppl don't.

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  5. Good argument, nice use of the meter.
    There is some discussion of reasonable CO2 limits indoors is here.... should it be 700 or 1,000 ppm : https://www.nature.com/articles/d41586-021-00810-9
    Of course, CO2 might not be a reliable analog of exhaled moisture. https://www.nature.com/articles/s41579-021-00535-6

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  6. While not entering crowded spaces, indoor or out, this was my conclusion for the whole past year. I do wear masks even outdoors if I can't stay several feet away from people, mostly as a matter of curtesy. Fortunately my favorite grocery store is large and would have only a few people present before 7am and I would do my shopping at that time about every 8 days. No restaurants indoors or out until we had our vaccines, and even now not often.

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    1. Exactly true for me as well

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    2. Ditto. It is more a courtesy thing than anything else. It is also symbolic. To some that means BS, but is there much difference between symbolism and BS?

      Indoors is a different matter. You are saving lives when you wear a mask (maybe your own).

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  7. Although logical, I am not sure how this observation ("the threat of outdoor COVID-19 transmission very, very low") squares with known outdoor spreader events such as FL spring break and WH Rose Garden ceremonies. And doesn't CO2 settle to the ground, as it is heavier than the air around it?
    But on a basic level, wearing masks everywhere in public is easier than having a whole collection of complicated wearing rules (going from outside to inside, etc) and is a small price to pay. So let's keep with the masks in public for a bit longer, until we know that we have a majority of the herd vaccinated, shall we? Science or not, there is politics and common respect for others involved.

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    1. For spring break and the Rose Garden there are indoor "events", so you really can't classify them as outside only. And in the Rose Garden events people were not moving. Because of winds, the CO2 generally does not settle to the ground in the lower atmosphere. People are welcome to wear masks outside if they want...my point is that they don't need to and a lot of folks are needlessly stressed and worried when a biker or jogger passes by...they should not be. And closing parks is unwarranted and counterproductive.

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    2. Is anyone closing parks now though? I agree, it was stupid to do that in the past, but that is ancient history now.

      I get your point about freaking out. But as pointed out above, it can be a courtesy. Chivalrous men get on the elevator first -- do they really think its going to fall? Moving to the other side of the street (or putting on your mask for a few seconds) is just a nice gesture, to tell the other person (who might be very worried about the situation) that you care about them.

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  8. I’d be interested in the readings on a commercial airliner.

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    1. Readings of CO2 in an airliner would me misleading. Most airplanes recycle the air at a very high rate, and renew it at a much lower rate (but still high compared with an office building or a shopping mall). The recycled air is filtered using HEPA filters that are very efficient at filtering out viruses, The air coming out of the filters back to the cabin is very very safe and free of virus. However, the filter doesn't filter disolved gases like CO2. So higher than normal readings of CO2 doesn't mean high levels of virus. Practically the only way to get infected in a plane is from the bigger droplets from a person seating very close to you (like next seat) or from touching a contaminated surface and then taking your hands to the mouth and nose without washing or disinfecting them first. Airborne transmisiΓ³n in a plane is very unlikely (but not unheard of).

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    2. CO2 measurements in airliners would be highly misleading because the air is recycled at a very high rate and using HEPA filters that are extremely effective at filtering the virus out, but not the CO2. If you are getting COVID in a plane it will be from the bigger droplets of a person very close to you (like next-seat close) or touching a contaminated surface and then your mouth, nose or eyes without sanitizing or washing your hands first. Not airborne transmission.

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    3. I took some measurements. <500ppm while flying, 1500-3000ppm while on the ground. I confirmed the lower air exchange rates with some Boeing and airport facilities engineers.

      This indicates that the typical risk analysis of infection on planes is incorrect because it assumes the <500ppm airflow the entire trip, but the 30-60 minutes on the ground has an airflow rate 1/10th-1/20th of that in the air.

      It was a bummer to take these readings, but it highlights how reportedly good situations can actually be very risky.

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    4. Those who doubt the potential for transmission during air travel should read this paper:

      https://wwwnc.cdc.gov/eid/article/26/11/20-3299_article

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    5. Good points Remnant and Allenr!

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    6. I'm pretty sure I have gotten the common cold at least twice from taking an airliner. No way to prove it, of course, but it did partially spoil my trip to Oahu.

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    7. Yep, I agree. What I said applied for an airplane in flights (or with the engines on and the PACs on). Boarding, deplaning and staying in the airplane on the ground in general has to be by large the most risky part of the flight COVID-wise. And don't take me wrong, I am not saying that you cannot get COVID in a plane (even in flight). If a guy with COVID in the contagious stage gets in the plane, the persons seated immediately next to that person are in a significant risk of getting it. But it is not like that person will contaminate the air and you will land with a plane full of infected people or something. In other words, air-quality wise, you are better off in an airplane than in a Walmart. But in a Walmart you don't rub shoulders with 2 strangers during 10 hours.

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  9. Cliff I am curious about the relative effect of elevation on CO2 and /or droplet transmission. Will fewer air molecules allow the droplets to drop faster? Or will the lower relative pressure allow them to travel further? Assuming wind is negated, should I be acting differently at Longmire Ranger station or perhaps the top of Rainier?

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  10. What is the rise time of your sensor and does it record a max value? Just curious if it is fast and sensible enough to catch one unmixed breaths passing by versus itself averaging the air moving around (which would be the case if its 95% rise time is bigger than say 250ms)

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  11. Thanks Cliff,
    This has been my thought as well all year. I have been entirely comfortable being around others outside (with separation) without a mask, but wear one when others do for their peace of mind. While reading, I was wondering about cigarette smoke since you can smell that from a long ways away, glad you covered that as well. It’s nice to see some experimentation into what many have believed all along.

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  12. Great article! My question is this, by wearing a mask does this reduce the amount of CO2 we exhale or inhale from the air around us? Most of the mask we are wearing, don't filter down to a gas level; if you can smell through your mask, you can contract a virus! CDC states on their website that 85% of the people infected with COVID, wore a mask.

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    1. No it will not affect the CO2. Though I notice that a mask will often change the smell of things, which means that it is selectively filtering out some particles or adsorbing volatile components.

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    2. Also keep in mind that the primary purpose of wearing a mask is to protect others from your potential viral transmissions, not to protect you from theirs.

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  14. I do agree that outdoor air is mostly covid safe, but complicated rules, as many people have mentioned, simply can't be enforced, so we enforce mask wearing outside in certain places (UW as an example). I just wanna stay safe. Complicated rules are annoying and hard to enforce, so let's just wear masks until covid transmission indoors is low enough we don't need masks period.

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    1. My biggest objection to wearing masks is that if you wear glasses, you are at a disadvantage. It fogs them up, especially in cold air, but indoors too. Another advantage of 20/20 vision (not me).

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  15. Cliff, I think you are not mentioning one important aspect of the equation: Protecting others. Yes, of course airborne transmission of any disease is very unlikely in outdoors and very well ventilated areas. But airborne transmission is not the only way to get COVID. Say that a person sneezes and contaminates a surface like a bench (with droplets or by covering their mouth with the hand and then resting the hand on the bench). Then you come, touch the bench, and scratch your eye. You can get COVID that way. Of course, you wearing a mask will not save you from that. But the first person wearing a mask might. That is not an important factor in the middle of a trail, but it can be in a picnic area and VERY important in the gym where people breath heavily and sweats and all types of potentially contaminated fluids go out of your moth and nose.

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  16. Broadly I agree that outdoors is much, much safer than indoors.

    But given that I don't know when an errant cough might happen from someone else, or how responsible they've been in their behavior, I think it's prudent to put on a mask outdoors if you're going to be in relatively close proximity to someone else (within six feet or so), even if it's only briefly. If you can give people a wider berth, as I can when walking around my neighborhood, I generally don't worry about masking up, but that's not the case on a trail with other folks.

    I do find it a little disappointing that, knowing how close we are to reaching vaccine availability to everyone and hopefully reaching a critical mass of vaccinated population, that you'd write an article effectively downplaying mask usage. Even if people do over-mask when outdoors (and even if you're right that they probably do!), that seems like a much more minor problem than people being too lax about mask usage.

    Put another way: this article seems like it's intended to educate people how to correctly use masks as little as necessary. Even if it's completely accurate, that feels like a questionable goal, given how close to the finish line we are.

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    1. Chris,

      The essence of science is about gathering data and drawing conclusions, not driving toward specific social goals. Facts are independent of intent.

      In that sense, this is perfectly reasonable and useful article to publish.

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    2. Chris... why have you NOT noticed / realized that "THEY" keep moving the "finish line" ... ''Oh ! a neo variant / varients 😱 !! " ... Hmmmmmmmmm ?!?

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    3. Johnamar, science is not some inhuman, unbiased force. Cliff chose to gather data on this specific topic and submit it to his audience.

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  17. I don't wear a mask outdoors since it's only for walks in mostly empty neighborhoods. Nevertheless, in order to pacify the sheeple here who wear masks 24/7 (even in their freaking cars!), I keep a safe distance and often cross the street when I encounter the masked. I often hear others say that "we're never going back to normal" while wearing their masks, and I wonder just whom they're referring to.

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    1. Other sheeple & Inslee. πŸ˜‰

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    2. Yes, I just absolutely "see red" when I hear people say that we "will never" go back to what we used to have. I'm hoping to return to the day went you could go to a dance and kiss your new-found sweetheart.

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    3. I discovered masks help me a lot with my severe pollen allergies. Maybe some people are wearing them for that reason, you never know.

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  18. I took readings on an Airbus A320 and 737 in the last couple of weeks.

    In the air, both planes kept below 700, with the bulk of the measurements less than 500 ppm. I bet the 700 ppm measurements were due to exhaled air flowing to it, and the 450ppm was the concentration in the bulk of the cabin.

    On the ground the CO2 concentrations were MUCH higher. Both airplanes went up to 1500-3000ppm, showing 1/20th - 1/40th the ventilation on the ground. I confirmed this lower air exchange rate with some Boeing and airport facilities engineers. This indicates to me that the risk calculations assuming the rapid exchange of air in airplanes are missing the ~30-60 minutes on the ground with lower air exchange rates.

    I’ll probably still fly some, but I’ll be VERY careful about masking while the plane is not moving. I’ll get on the plane at the last moment, sit at the front so I can deplane first, and keep my mask on with no exceptions until the CO2 goes down.

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  19. Thank you for confirming what I have understood to be the case for nearly a year. I found the paranoia displayed outdoors disturbing. I'm very cautious indoors.

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    1. I'm with you Linda. I also find the masks disturbing, and creepy.

      But I think a lot of people like wearing the masks, even if they say they don't. It's something akin to carrying around a security blanket.

      It's going to take a long time for the population to unwind from this.

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  20. Interesting experiments, thanks Cliff. Supports public health messaging to gather and recreate outside whenever possible. But "outdoors" can mean many things. Biking along the Burke Gilman trail is different from (say) sitting for a few hours in a baseball stadium, or attending a crowded political rally. Sustained close proximity, even if outdoors, probably calls for mask use. And absence of evidence for outdoor transmission isn't the same as evidence of absence. It is very difficult to determine where and when transmission occurs, except in certain situations (eg, cruise ships, nursing homes, household contacts). Contact tracing is next to impossible for transient outdoor exposure, so even if it does happen we are not likely to detect it.

    I don't view mask use outdoors as "paranoia". Like many other readers, I view it as a courtesy to others. I put on a mask when I think I will be passing close to another person, even if just momentarily. Even if the risk is small, it's just so easy to do.

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  21. Thank you Cliff for the reminder that a simple understanding of outdoor transmission possibilities, without bringing in the emotional state of 'what might happen', is what everyone needs to comprehend. Think a bit like Spock - logically. Wearing a mask outdoors can be viewed as theatre, a performance for the benefit of others. Conversely, not wearing a mask, with basic distancing (and a friendly smile!) can begin to turn the SS Paranoia/Fear around.

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    1. YESSSSSSSSSSS !! You are SPOT ON Dennis ! πŸ‘πŸ˜‰

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  22. I would think, erring on the side of caution that CO2 levels in the range of 450-550 should be avoided if possible, or approached wearing masks. Referring to the data in the gym and ventilated restaurant.

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  23. THANK YOU for shining some light on how stupid it is to wear a mask outside!!! Sheeple in Seattle are so afraid!!! It’s amazing how paranoid they are. Take off your masks and enjoy life. If you’re afraid stay home and let others LIVE and breathe free. And I am not a Republican

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    1. Well stated Steve ... tis' too bad you have to be p.c. and feel a need to i.d. yourself politically isn't it ?

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  24. That is plausible for the wild type, but for example the UK variant (B 1.1.7) is up to 75% more transmissible and 60% more lethal. See - https://science.sciencemag.org/content/early/2021/03/03/science.abg3055

    I highly doubt that CO2 meter is getting instantaneous max. reading. If it's some consumer product, it averages out over 2-5 minutes.

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    1. My thought too. The CO2 reading is likely reliable in places where it's fairly stable, but it would need readings in miliseconds, and record a max value to evaluate the risk of breathing in droplets from people you cross on a trail. Of course outdoor is much safer than inside, but I don't think the experiment can prove near 0 risk.

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    2. You beat me to it. If this disease spread like measles, the nation (and the world) would have shut down almost immediately. This variant changes the nature of the disease, although it is still a lot more dangerous to be inside than out.

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  25. Older man here--74...with a couple of co-morbidity factors...and no shot yet!...I am holding out for the one-shot J and J thing...so, I live like an ambulatory mummy!...have my sons do the shopping, only go out for my two coffees--and mask up for that!...for many of us elders, we simply have to play it very conservatively, and mask up as a habit...Even after getting the vaccine, I plan on masking for awhile--likely through this entire year...and yes, it does feel like some sort of security blanket!

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    1. Hey Unknown !
      An EVEN older guy here ...80 years young - with a couple of co-morbidity factors too. I've been ''out & about'' since last March. When I go to a store to shop I have a clear plastic "shield" I've worn since this Sheeple fear-mongering campaign began - and - in spite of it continue to receive looks & body-language of fear - disbelief & disdain.
      My wife ( who is 81 years young - with a couple of co-morbidity factors ) - and I do NOT plan on getting a shot/s of any of the "experimental" vaccines.
      Tis' horrible that Inslee & like-minded politicos along with the media have instilled such a terror-ridden fear in the populace don't you think ?
      Somehow the thought that we as AMERICANS have the RIGHT & FREEDOM to choose & make our own decisions has been trampled by tyrannical & UN-Constitutional edicts.... sans a whimper by the Sheeple... kind of scary huh ? 😲😱

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  26. In better words, safety first. Wear a mask and eliminate risks.

    For example, 99.9% of the time workers are standing on the edge of a 6' drop they don't fall. Yet they are required to tie off with a harness that can support over 10 times their weight. Countless lives have been saved due to policies like this that "cut the tail" rather than bend to the "regression of means." Also look up "lock out, tag out" procedures for electrical work.

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    1. Check out Mike Rowe's "Safety First" explanation
      https://mikerowe.com/2020/03/walk-me-through-this-safety-third-thing/

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    2. Have you read the case study on Alcoa lead with safety first and it lead to increased performance and profitability? Also check out Oxford's Bent Flyvbjerg who's latest publications discuss the mindset of "cutting the tail" vs. regression to the mean. He's no Mike Rowe but he's widely considered one of the top experts on megaprojects and complexity.

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  27. As it should be, Safety First is a good mantra to live by.. Cliff is only trying to point out some of the factual data... not sound bites on the internet or other media by so called "experts/scientists".. it should not be a political statement whether you wear a mask or not.. which it seems to be.. Use common sense and be aware of others. normal stuff.. When I worked for a large natural resource company and was told I had to wear a hard hat 100% of the time I was out of my pickup.. and was "ticketed" for not wearing one under a roof while fueling my pick up I couldn't help but complain... safety rules are good and necessary.. but please allow for common sense and more importantly science and statistical analysis to be part of the solution.

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  28. "One suggested that the risk outside was not zero: imagine if you had a conversation with a highly infectious individual for an extended time at close proximity (within a foot or two), with little wind and the person was upstream of you..."


    I hug people who have the flu and do so with complete confidence that the other person can't infect me try as they might. (It's actually true that physical touching raises immunity for both parties, but let's pretend that isn't a factor.)

    All viruses have negatively charged needles. Our cell membranes have a negative field that would repel any virus that I might inhale.

    The membranes' negative fields do a bang up job already because they also repel the 380 trillion viruses inside us. The idea that a few extra viruses would make a difference requires ignoring the fact that negative charges always repel negative charges.

    We only get sick if our membrane potential is down due to such things as a poor diet or exposure to WiFi and 5G. What happens outside of us has no bearing - not dirty keyboards and counters or even if someone were to sneeze on us.

    IOW, there is zero need for incessant disinfecting, masks, shunning or lockdowns.

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  29. I refuse to wear a mask when I am outside and can maintain 6 foot distance. This isn't just a matter of convenience, there is alot of science that says the risk of getting the virus outdoors 6+ feet apart is near 0 and when I am climbing a steep high altitude trail or running I need all the oxygen I can get. When I go hiking in the national park I can count on someone saying why are you wearing a mask and another person saying why arn't you wearing a mask. A few weeks ago I was snowshoeing near Paradise and I met a vaccinated older couple who were wearing masks and afraid to get within 10 feet of me. My question to this older couple is are you going to live the rest of you're life in fear? If a vaccine doesn't make you safe then what does make you safe? Snoshoeing is hard work, if I had COVID I would not have the energy to snowshoe/work out. I hope more people can get past their fear and see things logically.

    ReplyDelete
    Replies
    1. Legions of athletes are working out with masks. You can simply wear one around your neck and slip it on when you pass by elderly, mask wearing people whom you might otherwise scare.

      Delete
  30. Cliff, back in June of 2020 when blogging on this very same topic, you wrote the following, "The other day I was biking down the Burke Gilman trail and an older women saw me coming and fled off the trail, pushing her mask tight around her mouth as she turned to face away from me. There was profound fear in her eyes". This, Cliff, is exactly why I wear a mask outside when I'm on a trail like the Burke Gilman. Any reasonable person must certainly admit that Covid is scary and confusing for many people (people, not "sheeple", despite what your CO2 meters might indicate. I imagine it is especially scary the elderly who are the most like to perish from the virus.. I decided that, in this confusing and sometimes scary time, I will wear a mask so that I don't scare old ladies off the Burke Gilman Trail. It's a simple and kind thing to do.

    ReplyDelete
  31. Unknown....It is fine to wear a mask if you want outside....you just don't need to. But I think it is important to start providing people with the information that will reduce their fears, which are not based on science but poor information. Helping them to reduce their unfounded fears is, perhaps, the greatest kindness.

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    Replies
    1. Based upon my observations over this past year, there is no convincing anyone of anything. I will choose, rather, not to scare old ladies off the Burke Gilman trail.

      Delete
  32. I hike a lot. Many trails are very narrow just a couple of feet wide requiring hikers to pass in close proximity in those situations it makes sense to pull up a mask. Double that if the up hill hiker is puffing like a steam train with the exertion. You may not be able to measure much of a CO2 rise but getting a face full of exhaled air does not sound like a zero risk activity. Watching my kid play soccer on a cold morning was a good way to see the extent of the exhalation field of each player when interacting and chasing down the same ball at close quarters.

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  33. This is consistent with what I have seen from my own attempts to dig up information on the matter.

    I carry a mask with me when I'm outdoors in a public area. I put it on if I expect to pass within maybe 10' of other people, mainly for the sake of their comfort.

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  34. Hi Cliff. How can I forward you the results of public records requests I have submitted to the WA DOH? I think you will find their responses interesting. Among some of the information: They only know the symptom onset date for 50% of all cases (yet somehow they include 100% with dates on their scary graphs showing dangerous trends), The PCR Tests they conduct are at 37 cycles and 39 (which can lead to many false positives), and they do not know anything on how non WA DOH labs are conducting tests or what the cycle thresholds for those labs actually are (yet they include them in their totals). Further, their entire data set for the entire pandemic is corrupted due to them aggregating non-like data elements into "cases". Essentially they are adding apples + oranges + bananas and calling them all apples. I have at least 5 other outstanding questions for them to respond to, but they said they will not be able to provide answers until September 2021!

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    Replies
    1. TSS, I would be interested in what you found. Send me an email or call my office....cliff

      Delete
    2. Truth Seeking Skeptic

      Based on what you are saying, it sounds like

      - They have Fuji, pink lady, and honeycrisp apples, but they're all apples
      - The dates the apples become ripe enough to pick is not always known, so sometimes they only list the date they are picked (PCR test date)
      - Sometimes the workers exaggerate how much they picked (false positive), but in terms of tracking the general trend of how much fruit the orchards produce, that's not a big deal since the workers tend to exaggerate by the same amount each time.
      - A few oranges (flu) and bananas (other respiratory diseases) are finding their way into the bushels, but the usual monitoring for those catches some of them, so there is at least a rough idea how frequently that is occurring.

      Delete
    3. iamlucky13 - no it's more like they have apples, oranges, and bananas and call them all apples. And then say record amount of apples were picked and that this is horrible and the trend of picking apples needs to be bent or flattened.

      Delete
    4. I'd be interested in seeing those public records as well.

      Delete
    5. Truth Seeking Skeptic, I was willing to play along at first, but you've taken your analogy to absurdity. A COVID case is a COVID case, regardless of whether it is associated with non-like data such as people getting tested due to respiratory symptoms or people getting tested due to presumed exposure. Those elements do not turn diagnosed COVID cases into presumed flu case or presumed hypochondria or presumed bananas.

      Lots of apples are a good thing and correlates with lots of apple pie. No sane person wants to flatten the curve of apple pie baking. Lots of COVID cases are a bad thing and has correlated with lots of people dying from severe respiratory illness. Any sane person wants to flatten the curve of people dying from painful illnesses.

      I can grant you the reasonableness of looking into how much uncertainty there is, such as due to high Cycle thresholds. I absolutely am suspicious that orchard managers like Governor Inslee would want to exaggerate how many apples they have in order to gain more authority, but it reaches the level of hysterical conspiracy theory when it becomes necessary to presume that thousands of medical researchers working in both public and private settings with a good understanding of topics like PCR testing are joining in the conspiracy, along with hundreds of thousands of healthcare workers caring for the extremely high numbers of people requiring hospital care for respiratory illnesses.

      Last note: none of this is intended as critical of Dr. Mass's point that many people have an exaggerated level of concern in low risk environments, like outdoors.

      Delete
    6. They combine symptom onset date (apples) + lab test dates (oranges) + date reported to county (pears) + date reported to state (bananas) + no idea when the case occurred so use the date they type into the database even if the case occurred months ago (plums) and then they call the total dates Symptom Onset Date (apples) and say there are scary trends and records being set for cases so we must lockdown, etc. Plus they have no idea how many of these fruit are the same fruit being counted over and over (same person being tested multiple times), or how many were presumed to be a fruit (presumed covid case) but later were found to be a pizza (ended up testing negative) and when it is found out they were counting pizzas instead of fruit - they do not remove them from the totals but keep calling them apples. Clear enough now how much of a fruit salad they've created? The graphs they showed are not graphs of total cases but when cases happened so they can demonstrate scary trends are happening to justify all these mandates. Except, It is impossible to show trends with the above fruit salad of data the DOH has created. Their graphs are false misrepresentative graphs using corrupted data sets.

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  35. The wind component should be discussed. Outdoors or in, convective diffusion is what it's all about. I don't think I'd be comfortable sitting in a fairly crowded outdoor stadium on a still day. Indoors the hazard is proportional to the number of people and inversely proportional to the level of ventilation, the ultimate being an airplane.

    In general, I just wear a mask outside to make others more comfortable. It's pretty easy to do, I'm used to it. Wallet, keys, phone, and for 2020/1; mask.

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  36. Thanks Cliff for this scientific study. Now I finally have something in my hand that I can show to other people. At parks, I often see people having potluck parties where everybody wears masks and briefly removes or lifts them only to eat. Isn't it better to just avoid touching things and washing hands frequently rather than obsessing with masks? And by removing or lifting your mask to eat or drink, you are actually touching your face and the mask increasing the risk of infection to yourself.

    It's too bad that in Seattle it has become such a social norm. Why do I have to wear a mask when I am out of breath walking up a set of stairs at a park? The result would be that I would be exercising less, which would be far worse. It's not just "a piece of cloth". It's a restrictive piece of cloth.

    I find it alarming and disturbing that people would walk out onto the street just to avoid being within 6 feet from another person on the side walk. I find it sad that a few days ago a woman was hit and killed by a driver in Lake City Way while she was walking on the street outside of pedestrian markings. While it is not known whether she was just trying to avoid being close to other pedestrians on the side walk, I observe all the time while driving and walking how people jump onto the street to keep distance from others, even when all parties are indeed wearing masks! Now, that's dangerous!

    If you are sensitive enough to wear a mask as a courtesy to others, then please be sensitive to drivers who get anxious about hitting you or other passersby who do not want to see how you get struck by a vehicle.

    Like the majority of drivers in Seattle, I am attentive to pedestrians, but why is it a driver's responsibility to step on the brakes because somebody decided to walk or run on the street just to make the point that they are being sensitive? In my opinion, this it the result of the fear mongering and wrong information about how the virus spreads that the mass media and some politicians have been propagating. Bring on the science!

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  37. I generally agree with your conclusion about the outdoors. But some questions:

    - Do you have evidence that covid and CO2 travel in similar ways? On the bright side, covid might disperse faster by falling to the ground. But maybe not.

    - What is the relevance of your comparison with indoor home air? We know it's dangerous if someone in your home is sick.

    - How can you say that masks “probably aren’t needed” at the gym? Yes, the gym seems to have 1/7th the elevated CO2 (compared with baseline) of a crowded supermarket. But you spend more time in a gym, and much more time near specific people, and you inhale much more deeply.

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  38. Once again Prof Mass presents a rational - logical - scientific - fact-driven article to "correct" / refute the many faux articles & news surrounding a "hot" issue. In this case ... the scientific facts he presented are what anyone with common sense would have thought ... and Cliff just effectively nailed it down.
    The "damage" that the fear-mongers in the state houses & the media have caused is HUGE & horrible ! The losses of jobs - entire businesses ( large & small - many / most that will NEVER return ) - the suicides - domestic violence - increased alcohol & drug abuse - losses of over 1 year of education for kids ages Pre-school thru high school - as well as college / trade schools has wrought disaster. An article in yesterday's local paper told of how many people are DREADING IN FEAR a "return to normalcy" = psychologists & psychiatrists call it "re-entry fear" - and "cave syndrome". They indicate that the increase in patients & referrals are for: anxiety - depression - fear of people because they could make them sick or kill them.
    I have noticed this myself when I ( who is TOTALLY maskless ) am on a walk on the street or the highway where we live - as well as on a hike ... MOST people are wearing masks - and when I approach or pass them - many of them look at me like "deer in the headlights of a car" = fear-ridden ... or - they swerve waaaaaaaaay out of my way to avoid any exchange of words - eye-contact - or sharing of fresh air.
    What will happen ... IF or WHEN this ends ... and EVERYONE will have to "re-enter" the world ? Given the effects it has wrought so far ... with others emerging ... it is a tad scary !

    As Professor Mass plainly stated ..." Importantly, there is no compelling published research that demonstrates significant outdoor transmission. Outside air is very safe, and it gets even safer during the summer since ultraviolet radiation rapidly kills airborne virus. The logical conclusion from these results is that wearing a mask outdoors is probably unnecessary."

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    1. Very well described! I wear a mask only inside a business (e.g., restaurant or store) or an entity that explicitly requires it (e.g., school or university). I understand why they require it. They don't want to be sued and I don't want them to be sued.

      Delete
  39. You are not an epidemiologist, nor should continue to portray one on line.

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  40. The saddest example of people falling prey to the rampant fear mongering being pushed by certain groups is wearing a mask while driving their car by themselves with the windows rolled up.

    Sadly, there are folks that simply do as they're told without educating themselves about the threat they are responding to.

    Fortunately, Dr. Mass has once again offered up a science and fact based response to the fear mongering. Thank you!

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    1. I used to think that, but then realized that some of them are driving between places and don't want to keep pulling their mask off/on. They may just get used to keeping it on.

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    2. Also, if you wear glasses, when you get the mask just right and it's not fogging up your glasses, you don't want to mess with it if you're just driving to another place where you have to wear a mask. Also, there may be kids in the back seat that you can't see.

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  41. I find it striking that most commenters have no problem understanding that virus transmission is unlikely outdoors, but they almost all seem to think that using a mask will make a difference in virus transmission. But there is strong evidence that wearing a mask in public makes no difference in whether or not you will be infected with the SARS-CoV-2 virus. To quote an article on the subject by Dr. Sebastian Rushworth:

    "Wearing face masks when out in public does not meaningfully decrease the probability that the mask wearer will get covid-19. It’s possible that there is a small reduction in risk, but if there is, it is so small that it was undetectable in a study where almost 5,000 people were followed for a month."

    Here is a link to the full article: https://sebastianrushworth.com/2020/11/19/covid-19-new-evidence-on-face-masks/

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    1. Please, not Sebastian Rushworth. Just... no. Spend more time analyzing the flaws in his anecdotal thinking, as opposed to science based testing.

      Delete
    2. The primary reason to wear a mask is to protect others in case you are asymptomatically infected rather than protecting you, the mask wearer - https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html

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    3. The study that Sebastian Rushworth, MD refers to is indeed a randomized control trial. He point out himself:

      "The main thing lacking with this study is that it only looked at risk to the person wearing the face mask. It says nothing about the risk that the person wearing the mask will infect another person. That is an equally important parameter, and at present there are no high quality studies looking in to it, so before we can truly say that masks fill no function, we need another large randomized controlled trial that looks at the ability of face masks to prevent the mask wearer infecting other people."

      Even the link by the CDC provided by a commenter above does not offer any references to any scientific study whether mask wearing protects others from infection, only observational studies. You don't know whether communities that practice mask wearing may engage in other protective measures like hand washing or reduced social interaction. It is plausible though that in environments like airplanes where many people sit close to each other for longer periods of time the masks could have an effect. But even there, there are no randomized control trials. In my opinion, the benefit of wearing a mask outdoor does not outweigh the risk of me not getting enough fresh air, sunshine and exercise. Some people can stand it to jog 1/2 hour with a mask on, others can't. Let it be a user's choice.

      Delete
  42. Amazing how many say the mask up just to make others feel COMFORTABLE.
    You want to make me feel comfortable? Stop reaching into my wallet and taking 40% in tax dollars.

    ReplyDelete
  43. Studies have found that wearing a mask suppresses the immune system because of lack of oxygen as discussed in this article https://www.technocracy.news/masks-are-neither-effective-nor-safe-a-summary-of-the-science/. This indicates that both the protection from Covid-19 by wearing a mask and the potential for increasing the risk of Covid-19 because of the immune system being suppressed by wearing a mask must be considered.

    The CDC found that 70% of people who test positive for Covid-19 said that they always wore a mask outside their home in the two weeks before testing positive as shows in the table at the top of the fourth page of this report by the CDC: https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6936a5-H.pdf. In addition, polls such as the Gallup poll found that about 44% percent of all people always wear a mask outside their home as discussed in this article: https://news.gallup.com/poll/315590/americans-face-mask-usage-varies-greatly-demographics.aspx. Since the percentage of people who test positive is about 10%, in a sample of 1000 people there would be about 70 people who test positive who were also among about 440 who always wear a mask and about 30 people who test positive who were also among about 560 who either often or sometimes or never wear a mask. This indicates that people who always wears a mask have about a 70/440 = about 16% chance of testing positive which is about three times more likely than the people who often or sometimes or never wear a mask who have about a 30/560 = just over 5% chance of testing positive which clearly indicates that masks may be doing more harm than good. Since any less CO2 measured in the air corresponds to the CO2 which is trapped by the mask being breathed back in as less oxygen gets through the mask while the holes in a mask need to be much larger than the coronavirus so that it isn't be too difficult to breathe, this is not very surprising.

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    1. This is nonsense. Do you honestly think that workers in dusty or chemical vapor environments, who have been using masks and respirators for DECADES, are experiencing high CO2 or low oxygen levels? People would be fainting. The idea of a simple cloth mask retaining carbon dioxide or inhibiting oxygen transport defies fundamental chemical and physical principles. If it were true we would use that process to extract CO2 from the atmosphere.

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    2. I believe the point of wearing a mask is to protect those around you. Mask up!

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  44. According to all studies I have read, facial masks provide practically no protection from viri indoors, either. Lose excess flab, consume a healthful diet, and get some sunlight exposure, and you will be as safe from the covid flu as one can be.

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    Replies
    1. Facial masks are very effective in preventing transmission indoors- especially when worn by the infected person. This has been known for a long time before COVID. It has always been the case that if you go into the ER with a suspected respiratory disease, the first thing they do is put a mask on you. I do agree with everything you said about diet and exercise.

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    2. Tell it to the millions who died who were otherwise healthy. According to studies? Which ones? List them. And they need to be from peer reviewed literature and not YouTubers anecdotes.

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  45. I think you need to qualify this for certain activities, such as organized outdoor sports. Studies have shown that transmission is higher for these, probably due to increased CO2 presence from exertion? Here on SJI we have just had to go back to virtual learning due to a relatively large outbreak in the school baseball team, among other things. I have also read that school sports may be partly responsible for the mid-west surge.

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  46. from what I have read, there is little transmission for outdoor sports, it is the indoor sports (e.g., basketball, hockey) that are the problems.

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  47. Of all people Cliff. You should know better that pushing the idea of citizen scientist pushing public policy. You rail about climate warriors out of there depth and using incomplete data or bad science to make claims. While I don’t necessarily disagree with you on outside transportation, there are way more variables than you and your CO2 detecter conclusions should be pushing policy on.

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  48. Tom A, people do sometimes pass out because of wearing masks at work as mentioned in this excerpt from the first article that I referred to in my comments:

    My wife and I dined out last night in a very empty restaurant and the young waitress was required to wear a cloth mask. I asked her how she was doing with the mask and if there were any side effects. She related that she was consistently short of breath (when away from the table, she lowered the mask below her nose) and that she had actually passed out because of it a few days earlier, taking her straight to the floor.

    Before mask mandates began workers in places where there were dusty or chemical vapor environments usually didn't have to wear a mask all the time since they are generally not exposed to such conditions all day. In many workplaces it is only necessary to wear a mask or respirator in parts of the workplace where ventilation isn't enough to make it safe to be without a mask or respirator. Strict OSHA standards related to ventilation and air contaminants tend to limit the amount of time during each day when workers need to wear a mask or respirator. Surgeons also don't have to wear a mask all day since they aren't performing surgery all day. People who work for an extended period of time in locations where the air isn't safe enough to breathe in many cases can get enough oxygen as they protect themselves by using a supplied-air respirator which uses an air hose to supply air from outside the danger zone. I expect that many of the people who always wear a mask outside the home have more oxygen deprivation than most workers who worked in dusty or chemical vapor environments had before mask mandates began. Wearing a mask for extended periods of time in addition to suppressing the immune system can damage the brain, the heart, the lungs and the kidneys as discussed in this article:
    https://rense.com/general96/Mask_Risks_Part3.pdf

    Evidence that masks do more harm than good indicates the possibility that one of the motivations for mask mandates is that they allow for protesters as they cause damage to be more difficult to identify from surveillance camera footage or if someone takes a picture of them without it looking suspicious that they are wearing a mask . There is also reason to believe that China has some degree of control over those who order mask mandates and other Covid-19 safety measures and wants to harm the US economy in such ways as by making it difficult to identify protesters who damage businesses and by ordering restaurants to be closed.

    While at first glance oxymorons such as jumbo shrimp don't appear to make sense, it actually does make sense since some shrimp are much larger than others. However since it is likely that masks increase the chance of testing positive because they suppress the immune system while they likely also increase the risk of other medical conditions and the risk of being injured because of passing out, it is nonsense to say that people need to wear masks much of the time for safety reasons when they most likely do more harm than good. This makes a mask mandate a dangerous safety measure which doesn't make sense in any way. Whenever I see a sign that says wear a mask be safe it's hard for me to decide between wearing a mask and being safe.

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  49. Ellen, in addition to masks being ineffective in protecting those around you, masks can sometimes even increase the risk for those around you. This excerpt from the first article that I referred to in my comments explains one of the reasons why:

    Considering those positioned next to or behind a mask wearer, there have been farther transmission of virus-laden fluid particles from masked individuals than from unmasked individuals, by means of "several leakage jets, including intense backward and downwards jets that may present major hazards," and a "potentially dangerous leakage jet of up to several meters."

    In addition, since people who always wear a mask outside their home don't always wear a mask when they are inside their home while based on reliable data appear to have have a significantly higher risk of testing positive, this increases the risk for others in their home that they will get infected and then spread it to them. Because of this, rather than it being that it protects those around you to mask up outside your home, what quite likely actually protects those around you is to mask down.

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  50. Findings show that nearly 80% of COVID transmission occurs through direct contact with the viruses by touching them. In other words, airborne viruses are not large enough clusters to infect people, unless you have severe health issues. Or, at least that's my understanding.

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