Ask HN: Do you measure and/or mitigate CO2 in your living space?
If so - how?
Also - has anyone moved away from gas stove since recent articles about the issues with fumes they emit into spaces?
Also - has anyone moved away from gas stove since recent articles about the issues with fumes they emit into spaces?
I have learned a lot while using it for a couple weeks. First, making a fire in your fireplace is great for ambiance but drags air quality down substantially. It eats up oxygen a lot and make the CO2 increase sharply. It also causes very high spikes in particulate matter (both 1.0 and 2.5 micron) from putting the burned byproducts into the air.
I also started improving the energy efficiency of our heating system by fixing spots in the house where cold air comes in. While this results in less energy used to heat the home, it causes CO2 to increase because there isn’t anymore large holes to bring fresh air in. This device helped me learn that CO2 is and energy efficiency are circular problems. The tighter my house is, the more I need to focus on ventilation - exhaust out and fresh air in. It sounds complicated but for me it just means opening windows throughout the house for about 15-30 minutes per day. That alone makes a major difference on everything - Radon, PM 2.5, PM 1.0, CO2, etc.
Lastly just want to mention that it’s amazing to me how fast CO2 levels can rise with just my husband and I in our living room watching a movie. Good ventilation is something I definitely recommend everyone start measuring and working on.
In practice what our mothers and grandmothers did, without having ever sampled air.
Some old reference:
(Although, who knows, that might just be a weird localism, just like “Guten Nacht, schlaf gut, träum süß von sauren Gurken.” which I was taught in Köln and nobody else I’ve talked to anywhere in Germany recognises, though when I say I learned it in Köln they all go “Oh, Köln, yeah, they’re all crazy like that”.)
But the general term, as a verb, is "Lüften" or specifically "Stoßlüften" for the shorter form that is often mandatory for apartments with modern insulation but lacking a proper vent system to prevent mold.
On a sidenote: an interesting folk etymology exists for the Rhineland word "Fisimatenten", meaning something like "shenanigans", deriving it from French "visite ma tente", literally "visit my tent": the claim is that mothers would advise their daughters to avoid "Fisimatenten" because French soldiers during the Napolean occupation might invite them (in French) into their tents for, well, shenanigans.
Exactly that.
To add, problems with mold are often due to insufficient insulation in some patches of the wall (like near windows), combined with humid air and insufficient ventilation. A properly insulated house should not form mold. But it is necessary to get humidity out, that's correct.
Wait, people don't ventilate their home anymore?
https://news.ycombinator.com/item?id=25332981
there are quite a few replies of people that reported how they were not familiar with the concept.
And I have to underline how the evolution of building practices (again that depends greatly on different countries/local uses) generally speaking tends to make houses more airtight than before, so that ventilating should be more needed nowadays (with the exception of mechanically ventilated houses).
* ERV: energy† recover ventilator (temp+humidity)
† Actually "enthalpy", but few understand that concept, so for marketing reasons "energy" is used.
This is an oddly named but somewhat useful concept for air conditioning because water that condenses onto an A/C coil delivers its enthalpy of vaporization to the air conditioning system. So you can add “latent heat” to “sensible heat” and get a sensible answer.
But this is all a bit silly in the winter. In the winter, the primary consideration is not the energy cost of vaporizing the water in the air. It’s the amount of water in the air, how to get it there, how to keep it there, and how much humidity is safe for the building envelope. I doubt anyone measures humidity in units of BTU/cubic foot.
Not very useful when it is -10C (or colder) outside.
Current building science best practice can be summed up in the saying "Build tight and ventilate right.".
* https://www.energy.gov/indianenergy/articles/build-tight-ven...
* https://www.nrel.gov/docs/fy03osti/26458.pdf
Building tight prevents conditioned (heated in winter, cooled in summer) inside air from escaping, causing you to lose/waste money. It also prevents bad outside air (bugs, pollen, dust, car pollution, too humid/dry/cold/hot) from coming in.
Ventilating right means taking stale air from bathrooms (humidity) and kitchens (cooking VOCs) and exhausting it, and at the same time bringing in fresh air from outside on your terms: through filters and tempered to match inside conditions. This is usually done with HRV/ERVs.
Harder to do with older homes that need to be renovated, but now part of the building code for new builds in many areas (ASHRAE 62 defines ventilation volume/rate requirements).
Yes, I'm aware of mean radiant temperature:
* https://en.wikipedia.org/wiki/Mean_radiant_temperature
That doesn't deal with humidity (and other things like pollen in the warmer months).
Obviously you need the double-entry exchanger: Air comes in at 5°C and is gradually heated at 18°C by the air exiting, which starts at 20° and is cooled down to 7°C. No external energy required, it’s a classic of neutral-passive buildings.
I think they're way under-appreciated, by my calculation they're almost at gas boiler prices in terms of £/kWh of effective heat (currently paying 6p/KWh of gas) - and perhaps particularly as someone living alone, 'spot heating' is great - so cosy by the fire in the evening, way hotter than I'd want to heat the whole house (room even) with gas. I just wish I had one in my bedroom (& perhaps bathroom) too, I wouldn't even need central heating (well, maybe I shouldn't be so confident before Jan...).
At AirGradient we measure a lot of classrooms and it is not uncommon to see CO2 levels rising to above 4500ppm just within 2 or 3 hours. We wrote a blog post some time ago highlighting this [1].
[1] https://www.airgradient.com/open-airgradient/blog/we-measure...
I learned a lot about the ventilation situation at my place by tracking CO2 buildup. I now know that the time I should leave a window open to get CO2 levels indoors to approximate equalize to outdoor levels is 10x longer than what my intuition suggested.
I also discovered that every time I felt the air was “stuffy” and I needed some fresh air, it actually corresponded to a spike in VOx levels. When mom was visiting over summer, we discovered she is also sensitive to VOx levels.
This is my first winter with airthings wave. I’m curious to see how humidity levels are impacted by trying to keep my house warm.
Commercial buildings have all sorts of rules under Ashrae in the US. Generally in commercial there is a minimum air exchange rate for occupied space. Pre covid it was being constricted for "green" energy initiatives in the name of energy and $$ savings. That restriction was allowed to be really clamped down on (more savings) if certain conditions were met like CO2 monitoring or people counters, both more tightly targeting how much fresh air people actually need and minimizing waste in conditioning outside air that isn't necessary. Post covid a lot of that got thrown out, commercial buildings are now generally over shooting OA exchange in the name of not turning these spaces into germ breeding grounds.
None of this really exists in the residential sector, but maybe it should. Homes in even the recent past are "leaky" enough to get enough outside air exchange for the low occupancy rates without actively conditioning and bringing in outside air. Some modern energy efficient homes that are wrapped and sealed extremely well might pose an issue to this.
By all means get a decent sensor that reads CO2, CO, PM1, PM2.5, and VOC. Radon if you are in a risk area. Your regular thermostat probably already gets you temp and humidity. It needs to have some way to do long term data logging, five or ten minute sample rate for a year for example. You really want to see how things are different across seasons.
With that data in hand there are plenty of things you can do if you need to introduce more OA to occupied spaces. Generally there are heat exchangers that can be dedicated to that sort of thing. Or a simple motorized damper opening up a small filtered OA duct on the intake side of the air handling unit. Ideally those devices would only be activated on unacceptably high bad air quality readings.
If I install a meter and find CO2 is high, do the Ashrae guidelines give me any leverage against the building management?
Already it's often too hot because I'm on the top floor and I think they run the heat for the people on the bottom floor who are cold and the HVAC system doesn't seem to be able to deal with this.
Zoned systems are supposed to be able to handle individual zone heating/cooling issues, floor to floor without question should be able to be controlled. Entirely depends on what is installed and how it is controlled. This is an area where cost cutting happens. Generally there's a ashrae spec saying there is a minimum of five degrees °F between heating and cooling.
So sure get a couple data loggers and report any findings to your manager.
The requirements exist in the IRC [1] but are frequently not enforced in many jurisdictions.
[1]: https://www.energyvanguard.com/blog/2018-building-code-makes...
Green Building Advisor (https://www.greenbuildingadvisor.com) is a great community for such things, with a 99% residential focus.
I have an ERV in my house, running continuously. There are some great pieces of equipment out there, but they require conscious consumers and/or progressive code enforcement to end up in use.
Aside from the smell of beer, it was like stepping out into the Swiss Alps. I've never understood why rich people will spend $40K on audiophile equipment yet put up with crappy phones; I did a BBC interview remote in their NY studio using a $10K mic and the difference was staggering. Here, I swore if I ever got rich I'd want good indoor air.
It turns out I can afford to redo my house in California with a heat exchanger. I'm certain the hardest part will be finding a contractor who will exceed standards. Standards are why I have 1/2" pipes under my house. I want the bleeding edge of what's possible in my lifetime.
I can only recommend you do the homework and tell them exactly what you want installed. ie; be your own specification engineer. Anyone that's actually good at this sort of work goes commercial exclusively, that's where the money is.
You're saying, same drill here.
I think it has become clear that germ loads can be reduced significantly with filtering and ventilation.
The weird thing is it seems to mostly spike at night time and even more so on the weekends.
I have a few hypothesis, such as: - furniture offgassing - us being in the bedroom - gas cooking in the apartment building somehow settling into our ground floor apartment at night? - it seems to be worse if we have the aircon on - it really only seems to properly dissapate when the windows are open and theres good breeze and there seems to be a correlation between that and the sun coming up?
Like bisecting code, you can bisect airflow with plastic (e.g. 6 mil polyethylene) sheeting. Move the VOC sensor between isolated zones, or use multiple VOC sensor logs to track dispersal time/direction, narrowing down potential sources.
> it seems to be worse if we have the aircon on
Central or window aircon? You could place a VOC sensor near the HVAC duct input.
There's good evidence predating the pandemic that sufficient air exchange can nearly eliminate respiratory disease transmission. Just as they learned long ago in London that one could eliminate cholera by not drinking sewage water, we understand that the air quality and rate of exchange of indoor air should approximate that of outdoor air. We're however too cheap to do anything about this; it will take more deadly pandemics to drive the needed infrastructure changes.
Do you wince at the idea of people in London drinking sewage water? Those ignorant savages? Yeah, that's how people in the future will look back at us, getting colds and worse all the time in indoor air cesspools.
As we breath out CO2, it makes a great way to measure whether we're changing the air in a room fast enough to keep up with occupant breathing. Wilderness air passed 400ppm as part of global warming. My Manhattan apartment is above the Henry Hudson Parkway, and I can tell the time of day and day of week from the effect of traffic on my CO2 meter. I'm lucky to ever get below 450ppm.
The Aranet works far better than a $30 meter at the measurements a $30 meter will make, such as humidity. By appearance and build quality it's in a different league. CO2 is a bonus.
Considering Mauna Loa surpassed 420ppm in June 2022, I think 450 for New York City is indeed exceptional.
I'm now at 728ppm after cooking lunch, windows closed. There's a good kitchen exhaust to a roof fan, so I can get that number down a fair ways by cracking a window.
And I've been absolutely gobsmacked to discover just how much my mental clarity and energy are linked to CO2 levels. Above 1200 I'm just kind of out of it -- I function but my thinking is like half-speed, 700-1200 is much better but still not optimal, whereas basically 600 and below I've got the energy to do anything. And I'm still "shocked" at how this is a recent discovery, and not common knowledge at all.
So now, I keep a single window open a crack all year round to keep levels below 600, and actually change how far it's open as needed depending on what the sensor says. On a room-temperature still day I might actually need it wide open because the air barely enters, while on a freezing windy winter day it only needs to be a couple millimeters open. Interestingly, my electric bill hasn't gone up by any obviously noticeable amount -- I think because so much of heating/cooling is "stored" in the walls/floor/furniture/etc., not just the air.
I haven't moved away from a gas stove because I rent instead of own, but it's shocking how quickly CO2 and PM2.5 rise, so I keep my vent hood blowing full blast while cooking, and also open multiple windows. I don't close the windows until both levels have returned to normal.
(Although you could have just gotten a defective unit too.)
I observed it was useless and returned it.
Fixing or documenting their failures is effort for someone else.
[0]: https://na.panasonic.com/us/home-and-building-solutions/vent...
I worried about CO2 and general air quality in the office, particularly at those moments when coming back for lunch and noticing a “loaded environment” for lack or a better word. Not a problem anymore thanks to remote work :D
I feel like I'm very aware of bad air quality, especially in the office, where many people don't seem to care at all.
Definitely one of the biggest benefits from working at home for me, in the office I always felt exhausted after 1pm just because the air quality was so bad and airing was usually discouraged by angry looking coworkers ;)
There is no good solution for substantially mitigating CO2 in a living space other than ventilation. I also have an AlgenAir, and I love the business, but it can't on its own consume enough CO2 to compete with human production in a closed area. 100 devices- 2000+ plants equivalent- is what the CO2 absorption math says would be needed.
Since I couldn't find an affordable consumer device, I build one myself. Levels in my living room never really exceed acceptable levels. My house is not airtight and constantly mechanically ventilated.
They have to pry my gas stove from my cold, dead hands. I refuse to accept indoor air quality deteriorates that much when using a proper hood (that means turning it on before igniting your stove).
> I refuse to accept indoor air quality deteriorates that much when using a proper hood
That doesn't say much about air quality WITH hoods in general, let alone my situation in particular. Incidentally I was already planning to build a little sensor array, specifically for the kitchen, that would would measure some of the nasty stuff.
But even if I would measure that stove is slowly killing me, I wont give it up. Just like I won't give up my coal fired barbecue.
The burners go from 1-10 by halves and on 10 the big burner will boil a big-ass stockpot of water in what feels like a minute or two, and that's all I can use it for. 10 is literally too hot to sear meat, it will char it (and set off the smoke detector, apropos of the thread - it's a townhouse so of course the kitchen is right at the fucking center of mass of the house so the other rooms can have better light). It's also super-responsive and lets me get great heat control, if I go from 5.5 to 4 I can see what's happening in the pan change almost instantly. I never had a really fancy gas stove, but the ones I had were certainly not this responsive (although they sure beat the many crappy electric stoves I had).
It adjusts with buttons instead of a knob, which I kind of hate (a lot harder to work while cooking) but obviously that's not a comment on the heating technology.
/rant
The SCD30 generally seems to report higher CO2 levels than the MZ-14A. I believe it is probably more accurate because of it's calibration technique.
Both are NDIR based sensors.
Next I’ll try with a Arduino ESP32 thing. The sensor was expensive, it has to work. :-D
I live in a duplex, which means there's _a lot_ of air volume and mostly just me, so CO2 levels don't skyrocket and won't even reach 1000ppm after the whole day. I usually blast the windows open for a few minutes first thing in the morning and that does the trick, bringing levels down to ~500ppm.
What's worth mentioning is the massive temperature difference in between the top and the bottom floor, which is from 3 to 5 degrees Celsius higher upstairs. CO2 is also higher upstairs, about 150ppm, and P2.5 is usually higher downstairs (do they fall to the ground?)
I'm taking one of the sensors to my parent's this week, since they use a closed log burner to heat the house and I'm curious what the levels are going to be.
Last anecdotal point, I was fitting a Bosch Athlete upright vacuum cleaner with new VTC6 batteries for extended battery life and increased suction power this weekend, which requires a lot of soldering iron and tin, and I was amazed at how the PM2.5 would go crypto-style _to the Moon_
[0] https://www.airgradient.com/open-airgradient/instructions/di...
I recently got a semi-credible-looking non-IoT air quality monitor (CO2, TVOC, PM1, PM2.5, temp, humidity). I can't say how good the self-calibration is, but when the readings vary up/down usually seems to make a lot of sense.
For CO2 (and other air quality concerns in this problematic old student apartment, in a crazy university neighborhood housing market), I almost always have a couple windows cracked open.
And, if I haven't had a central window open wide for awhile, I'll try a large air exchange with outside, by opening many windows wide for a few minutes.
Interesting. My wife and I both realized over the pandemic that we are histamine sensitive (her much moreso than me). We have had the symptoms most of our lives but I do wonder is gas stoves make it worse. We stay in places with gas stoves sometimes, often with poor ventilation in the kitchen. I will have to see if there is any correlation of the severity of our symptoms.
I've hypothesized it is caused by overheating cooking oil.
Before induction cooking, gas stoves generally used to be able to provide more heat than electric ones. So its easier to cook hotter and burn more oil with those stoves.
Might be something else entirely in your case.
No.
> mitigate CO2 in your living space?
I open the window occasionally and when they are not open the are pretty draughty windows.
We got a new air exchanger installed, connected to our existing forced air hvac system. It runs at a low speed 24x7, which keeps things at a reasonable level.
It has a few settings like: continuous, 20 minutes/hour, 40 minutes/hour, and "humidity control". Nothing for CO2 control though. I have aspirations to hack the control module and make it care about CO2, but I've also got two kids and a startup so who knows how long that will spend in the backlog.
It's a big problem for me, as living in Florida basically means the AC runs almost year round. In the colder months we open the windows as much as we can to let the levels drop, but from spring through autumn it's just too hot to keep them open, as it just pushes the AC harder to cool more and more, while also increasing the humidity.
We definitely started getting better nights sleep once we had either the windows open, or the door to the bedroom open. I also rarely shut the door to my office as I was getting so sleepy at my desk during the afternoons.
I have no real solution for the hot months anymore, as Awair has basically abandoned the units I was using. I've just had some Zigbee air quality monitors arrive that I ordered on Aliexpress, but I'm skeptical at how accurate they'll be. Infact I'm skeptical at how accurate any of them are after I did some research into building my own and adding some sensors to an ESP32.
Going to have to try and come up with some HomeAssistant automation task with the Zigbee sensors and Ecobee to push fresh air through the house.
And that build-up of the stuff is a big difference to where we were living before (Edinburgh) where that kind of ventilation was basically unnecessary because no window closed that hermetical (well we lived in one of those wonderful 140 year-old houses in New Town).
In the end, with good insulation, it becomes increasingly important to have some active ventilation - it is also more economical, because it saves on heating. And that is in fact becoming more widespread with new family houses.
(Chiming in to diminish sample bias.)
I took it to the office one day and it measured 2000 ppm. It turned out one of the motors that brings in fresh air in the ventilation system had failed, I wonder if it would have been noticed without the meter. It's a great little device.
This system works well, the sensor is on my desk, the CO2 drops quickly below 600 ppm when the window is open, but then immediately returns to above 800 ppm shortly after the window is closed. For example, I currently have 982 ppm.
At night, with 2 people sleeping in the room, the level often rises to 2500 ppm. So even though I ventilate the house much more often than I did before I bought the sensor, it's still not enough to maintain healthy CO2 levels, and with the current energy prices and cold weather, I don't know what else I can do, I have no space to install heat recovery ventilation.
I had never monitored CO2 at home, and now I see that it routinely goes beyond 1500 in the living room. I can open windows and in 5 minutes it goes down to 700-800... together with all the warm air that was costly to produce now that's winter and it's so cold outside. And in 1 hour it goes back to 1000+.
So I've ended up getting used to see and ignore its metrics, because the alternative is to open windows every 60 minutes and lose a lot of money on heating.
(Or, those homes correctly have a "make up air" duct installed, which resolves this scenario)
We recently rebuilt the wall that houses our hood for our propane kitchen range. It's 4 inches, and I asked how difficult it would be to move to a 6 inch duct, since it's far more volume of air to be moved. Of course, the answer was a logistical difficulty and out of budget.
On particularly damp days in the winter here in New Hampshire, if someone accidentally leaves a bathroom fan running, and perhaps the kitchen hood, it can be nearly impossible to get a wood stove fire going. So although these electrical systems are not drawing what seems like a lot of air, they have practical effects on unrelated systems.
On CO2, we observe mostly three different use cases:
CO2 as an approximator of Covid infection risks: With the possibility to use CO2 levels as an aproximator of aersols with potential virus load, CO2 became quite popular as a measure about how effective the ventilation works.
CO2 as an indicator of cognitive performance: There are a number of studies, e.g. [2] showing a clear link between high CO2 levels and impaired cognitive performance. I am seeing more and more people that especially want to measure CO2 levels in order to keep them low and have a better working environment.
CO2 as an indicator of ventilation rates: Without ventilation, indoor pollutants e.g. harmful gases from furniture, colors, building materials etc. will increase. Some of them can be measured as TVOCs but not all of them. Low CO2 values indicate a high rate of air exchanges and these typically flush out these indoor pollutants. Ideally the HVAC system uses HEPA and carbon filter for the fresh air intake to ensure that the air coming in is clean. In climate zones with a high differential between indoor and outdoor temperature, heat exchangers should then be used.
If you measure more than CO2, but also PM and Temperature and you have the ability to control your ventilation rates (either by manually opening windows or by a demand controlled HVAC system) you can see and optimize potential tradeoffs, e.g. cooling or heating energy is wasted by increasing fresh air ventilation rates or opening windows will bring down CO2 but increase PM if you live in a polluted area.
Regarding the OPs question on moving away from gas stores. Here the new TVOC sensor from Sensirion SGP41 [3], that can be uses in our open-source open-hardware air quality monitor [1], is able to measure NOx and can be a good indicator if your stove emits fumes into the living area.
[1] https://www.airgradient.com/open-airgradient/kits/
I use its API to connect to it once a day and download the last 24hrs of logs (it stores 14 days worth on the device).
It's expensive - but it's really the best there is IMO.
I try to open a window on either side of the house when the co2 gets over about 750~
Winter is the real concern. Not much opportunity to air out the house when the temp is consistently below 20 degrees Fahrenheit.
I supposed I should look into a heat exchanger.
this is the right order of concern. pollution (particulate matter) is much more damaging to our tissues than CO₂, which is basically inert in comparison (e.g., people die of smoking, not working in a stuffy office). life evolved alongside CO₂, but not so much alongside NOₓ, SOₓ, CFC/HFCs, dioxins, and the like. but in every thread about air quality, the majority of the discussion is on CO₂. the mediopolitical narrative is driving hard in this direction, to our detriment, as plainly evident here.
The conclusion is that we need to ventilate more. Especially in the bedroom. Sometimes it’s hard to find a good balance between ventilation and heating.
I keep wondering if CO2 is the reason that so many cars try to force recirculation off. I am super sensitive to exhaust fumes so I am constantly turning it back on.
I've used a cheap car though, and it shuts off recirculation using a timer. Maybe it's different in more advanced models.
The sensor may be inaccurate, although it's one of the better ones if you're not willing to pay hundreds of dollars. After living for many years at similar levels of CO₂, I don't really feel them at all, so it's hard to (dis-)confirm these findings.
Determined my kids rooms are big culprit with doors closed. (Up to 1400 at night) now keeping door open.
I doubt this will fly when they are older so looking into installing an ERV/HRV system if anyone has any recommendations.
I really don't have the information to weigh this either way but I've considered closed doors a safety measure for years so this throws me off in an unsettling way.
it's just missing the airgradient https://www.airgradient.com/open-airgradient/kits/
I've found that I need to keep my bedroom door open at night, to keep Co2 levels below 1000 PPM. Also, I need to increase my apartment's ventilation by one or two levels for board game nights (or whenever there are 4+ people present).
https://www.amazon.de/-/en/Dostmann-31-5009-AIRCO2NTROL-Moni...
Since then, I don't monitor any more and I don't miss it as I'm always airing the room multiple times per day anyway and I didn't really get something out of it except some pretty graphs.
There's not much else you can do. Even in the winter, I open it long enough to change the air and hopefully without letting the heat escape too much.
I used the old generation Awair, they are no longer supported. Now it reads false readings about air quality, so I'll be switching to one of the competitors. Good things is that Awair seem to have opened the door, there was not a lot of devices a few years ago and now there are a more options.
(At sane levels, the effect is negligible.)
Cf. recent discussion on amount of daily rosemary growth it would take - https://news.ycombinator.com/item?id=33577929
It's CO that's an issue, and related to incomplete combustion.
I use an BlueAir 680i, so indoor air is cleaner than outdoor.
During winter nights we routinely hit 3k-4k in the bedroom by the morning. During summer it never went over 900 due to open window.
Solution, get up in the middle of night to open balcony for a few minutes, drops to under 1k very quickly.
When we run the gas stove, I try to run the exhaust fan.
Mitigation - one of my bedroom windows is rather leaky & I've decided to leave it as is due to co2 concerns.
And even if it is on, the CO2 at least initially won't be super hot and instantly go up; as flame hits the cookware it will cool down to the temperature of it
That was enough to lower CO2 levels to the bottom of the sensor's sensing range.
And from studies I read the issue with gas stoves are pretty much exclusive to developing countries with bad stove standards and poorly ventilated kitchens.
We use electric stoves, but would prefer gas.