[HN Gopher] Training my sense of CO2 ppm
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Training my sense of CO2 ppm
Author : truxs
Score : 42 points
Date : 2022-07-16 21:17 UTC (1 hours ago)
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(TXT) w3m dump (interconnected.org)
| kadoban wrote:
| Is there any kind of CO2 scrubbing that's at all practical for
| home? I'm curious what the effects would be of going below
| ambient/outdoor levels, especially since those are rising (if
| slowly).
| CoastalCoder wrote:
| From some (personal) research I did several years ago, I think
| good ventilation is by far the biggest concern.
|
| A well-sealed, occupied room can build up significant CO2
| levels pretty quickly. In my particular case, one person, not
| exercising, could bring CO2 above 800ppm (reported) in just a
| few hours.
|
| So I think lack of ventilation causes way, way more excess CO2
| than is caused by recent increases in atmospheric CO2. At least
| in my suburban neighborhood; maybe it's a lot worse in a dense
| city.
| kadoban wrote:
| My issue with that is that in the summer, ventilation is
| ~impossible. It's 110 degrees out there, reasonable
| ventilation would mean either burning out my A/C or living
| with temps that are far too high.
| CoastalCoder wrote:
| Interesting problem. Mind sharing roughly where that is?
| kadoban wrote:
| Ah, yeah, Phoenix summers. I believe parts of Texas and
| some other places are somewhat similar.
|
| In the winter the situation is _much_ better, but
| probably 4 months out of the year, the outdoors are
| unlivable.
| jasonpeacock wrote:
| Due to climate change, that's could be pretty much
| anywhere it's summer. E.g. check out the UK:
|
| https://www.metoffice.gov.uk/about-us/press-
| office/news/weat...
| [deleted]
| Retric wrote:
| Simplest solution is a high efficiency air to air heat
| exchanger to let you circulate a lot of outside air. They
| are less efficient when dealing with high humidity, but you
| can have this as part of your HVAC system and never really
| think about it.
|
| https://en.wikipedia.org/wiki/Heat_recovery_ventilation
| kadoban wrote:
| Interesting, I don't think I knew that was an option.
| I'll look into it, thanks.
|
| I rent right now, which means I doubt I can, but hoping
| to buy soonish.
| danans wrote:
| If you do this (install an HRV), expect it to cost many
| thousands, and make sure all your duct-work is running
| through very well insulated spaces, or you will obviate
| the heat recovery part, and you will just have a very
| expensive ventilator.
| [deleted]
| [deleted]
| [deleted]
| danans wrote:
| > Is there any kind of CO2 scrubbing that's at all practical
| for home?
|
| Not scrubbing in the way that a power plant does, but you can
| improve ventilation, but you probably need to do more than
| crack a window.
|
| Options from cheapest to most expensive (in upfront cost):
|
| 1. Run your stove extractor fan (assuming it is externally
| vented), and open the window that is furthest from it in the
| house.
|
| 2. Open 2 windows and put a fan in 1 facing out, and if it's
| winter, wear a sweater.
|
| 3. Install a whole house ventilation fan (i.e. Panasonic
| Whisper Green fan) and keep the furthest away window slightly
| cracked.
|
| All of the above will cost less upfront but will result in a
| significant increase in your heating/cooling energy use during
| hot/cold seasons. If you want to minimize the increase to your
| heating/cooling energy use, then you need to spend more upfront
| and:
|
| 4. Install a whole house <heat|energy>-recovery-ventilation
| system. This system brings in fresh air 24/7 while transferring
| much of the heat/"cold" from the conditioned space to the fresh
| air from outdoors.
|
| What all of these solutions share is that they don't rely on
| wind/convection to ventilate the house, they are all
| mechanical.
| timothyb89 wrote:
| By far the simplest solution is to just crack a window. Even a
| modest amount of fresh air exchange is enough to offset most of
| the CO2 generated by the people inside.
|
| I use a relatively small 10x11ft spare bedroom as my home
| office. If I close the door and window, it'll quickly climb
| above 1200ppm after 15-30 minutes (and set off an alarm on my
| sensor). It'll cross 1500ppm easily if left unchecked. HVAC
| helps but gets outpaced quickly if my apartment windows are all
| closed.
|
| That said, keeping doors open, running HVAC normally, and
| cracking a small window open, even 1-2 inches and on the
| opposite side of my apartment, is enough to keep CO2 levels
| around 550ppm while sleeping and 700ppm (in occupied rooms)
| while awake.
| Aulig wrote:
| I have a qingping air monitor lite, which was around $70.
|
| It also measures PM10 and PM2,5 which helped me show that my wood
| furnace is indeed leaking something sometimes when I noticed it
| smelling weird.
| CoastalCoder wrote:
| I think the elephant in the room is calibration of the CO2
| detector.
|
| When I looked into this a few years ago, I couldn't find any
| accuracy guaranties for CO2 meters marketed for households /
| greenhouses.
|
| The closest thing I could find were laboratories that could test
| CO2 meters in chambers with known CO2 concentrations. But IIRC
| the pricing for those labs was prohibitively expensive.
|
| - There were literally _no_ guaranteed accuracy bounds for the
| meters I looked at. So they could be off by 3x reality for all I
| know.
|
| - Their calibration systems relied on an assumed CO2
| concentration for outside air. But even if the calibration system
| ensured that the meter would report the right number for _that_
| CO2 concentration, there was no information about how accurate
| the calibrated meter would be at _other_ CO2 concentrations. Nor
| information about how the meter 's numbers would be off when the
| CO2 levels observed during calibration differed from the level
| assumed by the calibration logic.
|
| These limitations might not be a problem for some applications.
| But they could be an issue when people want to relate _their_
| meters ' readings to the numbers used in various research
| publications.
| greggsy wrote:
| If I understand correctly, they're calibrated at the factory,
| which is probably in China, which might have vastly differing
| CO2 levels depending on whether the winds blowing up or
| downstream of any heavy industry or metropolitan centre?
| ericd wrote:
| Not an expert, but I looked into this a bit a while back to
| see if one could reasonably tell emissions via differences in
| atmospheric CO2 concentration, iirc the conclusion was that
| CO2 concentrations don't vary much outside, air mixes pretty
| well, pretty quickly.
|
| Even seasonal fluctuation is just a few percent.
| ericd wrote:
| Well, if you take it outside, and it says a bit over 400ppm,
| it's at least roughly right at that point on its sensor's
| curve.
| GuB-42 wrote:
| If you don't care about errors of a few percent you should be
| able to make your own calibration chamber.
|
| You just need an airtight container of a known volume, a source
| of CO2 and a maybe a fan. Put your CO2 detector inside the box,
| with fresh air, your CO2 source and the fan, and see if the
| result matches. You may need to do some calculations.
|
| For your source of CO2, you have a few options: combustion of a
| known quantity of fuel, soda bottle, dry ice, acid + sodium
| bicarbonate,... If you want to remove CO2, you can use calcium
| oxyde (quicklime).
| saurik wrote:
| I own an Awair unit, and as far as I can tell it attempts to
| calibrate itself based on outside atmosphere having 400 ppm...
| but that value is constantly going up and is now like 415, so I
| figure my unit must be at least a few percent off.
| bbarnett wrote:
| I may be misunderstanding, but if you claim outside is 415
| and that's that, it's wildly inaccurate.
|
| Where you live, time of day, lay of land, all matters.
|
| Winter (no trees or vegetation with photosynthesis), and
| there is naturally more local CO2.
|
| Live deep in the country, in a forest, in the summer, when
| trees have loads of water and are at max output? Less CO2.
|
| At night, more CO2, for all those trees, that greenery, is
| breathing and exhaling CO2, with no sun for photosynthesis.
|
| It's variable, not static.
| bumbledraven wrote:
| Just how "wildly" inaccurate are we talking about? What
| should the outside CO2 readings actually look like under
| those conditions?
| abirkill wrote:
| The auto-calibration systems on cheaper consumer sensors also
| cause issues if they rarely see air that has low CO2 levels.
| Because these sensors can't measure absolute CO2 levels, only
| relative CO2 levels, they provide an absolute figure by looking
| for the lowest CO2 concentration they've seen over a period of
| time, usually around a 72 hour rolling window.
|
| This works acceptably if the sensor is frequently exposed to
| outdoor air, but in a residential environment that's not always
| guaranteed, particularly in winter when it's not uncommon to
| keep windows closed to retain heat. In these situations the
| sensor will consider the lowest level to be around ~400ppm,
| even if it's actually much higher. This, of course, scales all
| other readings, so a sensor might read between 400-800ppm,
| leading you to believe everything is fine, when the actual
| indoor range is 800-1600ppm.
|
| Because the auto-calibration happens over a period of time, it
| can be quite difficult to determine that your sensor is
| misreading, and the only way to fix it is to expose it to fresh
| air to reset the baseline.
|
| The best solution I found to this is a dual-NDIR sensor which
| measures two different light frequencies, one which is absorbed
| by CO2 and one that isn't. This allows the sensor to know the
| absolute CO2 concentration, rather than the relative CO2
| concentration, and avoids the need for auto-calibration. (I
| believe for absolute accuracy it still needs calibration for
| altitude, but for consumer use this makes such a small
| difference to be irrelevant).
|
| Unfortunately, when I last looked, I couldn't find any
| consumer-grade sensors which used dual-NDIR sensors, only more
| expensive and less aesthetic commercial sensors. In the end I
| built my own using a CDM7160 sensor connected via I2C to a
| ESP8266, which reports over MQTT.
| rootusrootus wrote:
| The Aranet 4 claims it can measure up to 5000 ppm with +-3%
| accuracy. But you'd have to take their word for it, I guess.
| For $250 I'm hoping it's not a crap sensor.
| MatteoFrigo wrote:
| The usual convention is that the accuracy refers to full-
| scale measurements. I.e., your device has an error of
| +-3%*5000ppm = +-150ppm. At ~400ppm you are about 37% off.
|
| Human exhaust breath contains about 5000ppm CO2, so this
| device is decent for measuring humans. It's less decent to
| measure atmospheric CO2.
| colechristensen wrote:
| I have a few CO2 meters from very different sources
| (professional exetech, consumer product, electronics component)
| and they have always reported levels within 10% of each other.
|
| For my purposes I don't really care about accuracy under 50ppm,
| higher precision for trends is useful but as long as the
| measures value is accurate to within 50ppm I'm just fine for
| effects on a human. If I was doing research to publish an
| actual calibrated meter for 10x the price would be warranted
| but having three separate measurements agree gives me the trust
| I need.
| binkHN wrote:
| > I'm looking forward to the day when I can walk into a room and
| say, huh, feels like 800 in here...
|
| I've been this way for well over a year now. Almost two years ago
| I picked up an air monitor from Awair (yes, this was a pandemic
| related purchase because I was working so much from home) and I
| frequently checked what the CO2 was. Nowadays, as it starts
| hitting ~750ppm, without looking at the monitor I can tell it
| feels "stuffy" and I open a window.
| whalesalad wrote:
| I feel terrible above like 900/1000ppm but I'm sure it's also a
| good proxy for whatever other garbage and voc's are in the air.
| When my monitor reaches 800 I'll throw my window exhaust fan on
| for a few hours to circulate the air in my home.
| dQw4w9WgXcQ wrote:
| We need a study on what will kill you sooner, the CO2 levels or
| the need to anxiously monitor whether CO2 levels are too high in
| every single enclosed space you enter.
| macNchz wrote:
| I've had an Awair monitor for a few years and enjoy keeping a
| fairly close eye on the numbers, but from what I've experienced
| so far I'm convinced sure I'd be able to train myself to discern
| CO2 levels. If anything it has mostly just encouraged me to open
| the windows, even just for a bit, whenever possible, and to
| _always_ use the kitchen exhaust fan with our gas stove (and
| motivated me to buy an induction range in the future).
| colechristensen wrote:
| Especially if you do things like stirfry or anything which puts
| char on your food, particulate from the cooking food will be
| way more than from the cooking gas so induction won't make a
| large difference.
|
| Ventilation and good hepa filtration will make a much bigger
| difference.
| moduspol wrote:
| Same here. I was truly surprised at how fast the CO2 goes up
| with our gas stove on. The only thing worse is when we use our
| unvented gas logs in the fireplace.
|
| We're switching houses next month and I'm seriously considering
| putting in an ERV. It's just a little tricky to explain to
| friends and family because it kind of makes you sound like a
| crazy person. But CO2 is measurable! And there is clear science
| about bad effects when it gets high!
| h2odragon wrote:
| people on supplemental oxygen sometimes get CO2 problems; the
| oxymeter shows good numbers but they're acting drunk or feeling
| poorly otherwise.
|
| Apparently its sneaky and cumulative; a few moments wont do much
| but as time goes on you get fizzier.
| EvanAnderson wrote:
| > ...but as time goes on you get fizzier.
|
| While I'm fairly certain you meant "fuzzier" I can't help but
| thinking about bubbly blood full of dissolved CO2.
| h2odragon wrote:
| I think thats pretty much the case.
| post-factum wrote:
| I've bought [1] and coupled it with Zabbix using [2].
|
| Now I have a pretty realtime graph and a strong reasoning to air
| my room more often.
|
| [1] https://www.tfa-dostmann.de/en/product/co2-monitor-
| airco2ntr...
|
| [2] https://codeberg.org/pf-monitoring/airco2ntrold
| ohm wrote:
| Not sure if they still make them with speakers that sound like
| life support monitors in the hospital, but if the beeping is
| too annoying you can just open the back and break off the
| speaker with pliers.
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