Whose breath are you breathing?

Covid aside, a reading of almost 6000 ppm in the bus is extremely high, at this level there is a clear impact on cognitive function.<p>See this study[1] in Nature that measured the effects of CO2 at 1000, 3000, and 5000 PPM. Quote: &quot;For the Psychomotor Vigilance Test, the probability of achieving an accuracy score of &gt;90% decreased in a dose–response like fashion from 79.5%, 74.7%, 73.4%, to 64.0% for 600, 1200, 2400, and 5000 ppm, respectively&quot;.<p>Another study[2] tried to establish the effect on response time, finding that &quot;For every 500ppm increase, we saw response times 1.4-1.8% slower, and 2.1-2.4% lower throughput.&quot;<p>For a more pop-sci take on this, see this Tom Scott video where a subject is placed inside of an airtight chamber where the CO2 gradually increases, with a major impact on their brain function: <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=1Nh_vxpycEA" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=1Nh_vxpycEA</a><p>[1] <a href="https:&#x2F;&#x2F;www.nature.com&#x2F;articles&#x2F;s41526-019-0071-6" rel="nofollow">https:&#x2F;&#x2F;www.nature.com&#x2F;articles&#x2F;s41526-019-0071-6</a><p>[2] <a href="https:&#x2F;&#x2F;iopscience.iop.org&#x2F;article&#x2F;10.1088&#x2F;1748-9326&#x2F;ac1bd8" rel="nofollow">https:&#x2F;&#x2F;iopscience.iop.org&#x2F;article&#x2F;10.1088&#x2F;1748-9326&#x2F;ac1bd8</a>

I hadn&#x27;t considered how bad public transport might be in terms of ventilation, but it makes sense. I wonder how bad the London tube might be on a busy day?<p>It&#x27;s unfortunate that research on the impact of Co2 concentration on cognitive function and general wellness is so inconclusive (ie: effect size of high concentration on most tasks seems small), when <i>subjectively</i> it feels really high.<p>Some years ago I did some datascience work with a housing association wherein they installed high-frequency sensors in various rooms of housing units across the country (with the explicit consent of the inhabitants, data anonymized) with the intent on understanding how building properties and use correlated with the sensor data. In general there was (and still is) a lack of understanding how to model the relationship between things like building material, climate, occupancy, tenant behaviour and negative outcomes like mold growth, fuel poverty&#x2F;health outcomes, and so on. I mean - I&#x27;m not saying there&#x27;s no understanding, but it&#x27;s definitely a field where more work is needed.<p>Anyways, one of the things I found most shocking is that in many of these flats, Co2 concentrations would get mind-bogglingly high in bedrooms during the months where tenants would likely have the windows closed (this is something you can infer by temperature gradients and heating usage). By mid-way through the night, some individuals were in rooms with 4k+ co2 ppm. A common side effect of breathing air with such a high concentration is waking up feeling groggy, disoriented, or with a headache. But what are these people supposed to do - many of these flats were low-income housing, so they&#x27;re badly insulated to begin with, and they probably can&#x27;t afford the heating bills of keeping windows open for ventilation.<p>Sorry for the long story - but the point is that there are many negative health externalities associated with poor ventilation in buildings and interior spaces, and at least we&#x27;re starting to get attention on the problem now with covid. Hopefully this leads to improvements across the board.

Interesting, but I see two big issues that render the data nearly meaningless:<p>1) does CO2 correlate well to spit droplets? they mention this (alleging that places with more talking have more spit droplets than ones without) but present no data. Also, does CO2 on public transport involve any exhaust from the vehicle? Are people in gyms breathing a lot with their mouth closed, producing more CO2 but not talking (or otherwise producing spit droplets) nearly as much. Lots of ways this could be not very correlated.<p>2) does quantity of spit droplets really correlate to likelihood of getting infected? Viruses are replicators. It is not at all obvious to me that 1&#x2F;2 the number of viruses means 1&#x2F;2 the risk of getting infected. It might not even result in a significant drop at all. Theoretically one droplet containing the virus is enough to infect you, and if infected it replicates. The operative factor is how well your immune system recognizes the threat and produces antibodies, not how many virus copies were there originally. One drop was enough to infect just over half of a young, healthy experimental subject group: <a href="https:&#x2F;&#x2F;www.science.org&#x2F;content&#x2F;article&#x2F;scientists-deliberately-infected-people-coronavirus-here-s-what-happened" rel="nofollow">https:&#x2F;&#x2F;www.science.org&#x2F;content&#x2F;article&#x2F;scientists-deliberat...</a>

Title reminds me of this:<p>&gt; Nowadays, at least in the population of the industrialized nations, about 40 percent of the nitrogen contained in the human body has already taken part in the Haber-Bosch synthesis.<p>(from the German <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Haber_process" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Haber_process</a> article)

Any recommendations for a good portable CO2 monitor?

In a related, but much more personal note: it turns out that we are breathing, on average, one molecule of Ceasar&#x27;s last breath [1]. And Jesus, Buddah, and a lot of other people.<p>[1] <a href="https:&#x2F;&#x2F;www.irishtimes.com&#x2F;news&#x2F;science-asserts-we-are-all-part-of-christ-s-body-1.255358" rel="nofollow">https:&#x2F;&#x2F;www.irishtimes.com&#x2F;news&#x2F;science-asserts-we-are-all-p...</a><p>(I know, it&#x27;s probably mostly BS -- I&#x27;d bet most of the <i>last</i> breath has been absorbed into the ocean, or plants, or whatever. But, over my lifespan, I&#x27;ve probably sucked down atoms of Jesuse&#x27;s breath during <i>his</i> lifespan. With that, who needs holy relics.)

Lately I hear about more COVID cases that presumably started on an airplane. Therefore I am now wondering how great these ventilation systems on airplanes really are, compared to, say, those in restaurants and theaters.

It sounds gross. But:<p>i) if we all drove cars, the result would also be bad<p>ii) I wonder if there are benefits from this (stronger herd immunity)

This reminded me of an undergraduate Physics professor who made us estimate the fraction of molecules in one breath that had been exhaled by Jesus. Fun times.

if high CO2 equals more risk of contamination then Japan should be getting large transmissions of COVID in over-saturated trains on a daily basis, but it does not. So this data seems more junk than anything else.

huh, all the places I would never go have terrible air.

all of it, I hope...<p>preferably mostly plants