[HN Gopher] Training my sense of CO2 ppm ___________________________________________________________________ Training my sense of CO2 ppm Author : truxs Score : 42 points Date : 2022-07-16 21:17 UTC (1 hours ago) (HTM) web link (interconnected.org) (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. ___________________________________________________________________ (page generated 2022-07-16 23:00 UTC)