Ask HN: Do you measure and/or mitigate CO2 in your living space?

[_njuy]

If so - how?

Also - has anyone moved away from gas stove since recent articles about the issues with fumes they emit into spaces?

[kylerush]

I recently started measuring CO2, Radon, PM (particulate matter) 1.0, PM 2.5, VOC, humidity, temperature, and air pressure with the Airthings Wave connected device.

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.

[throw0101c]

> It sounds complicated but for me it just means opening windows throughout the house for about 15-30 minutes per day.

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).

[ambicapter]

There's a ventilation technique that uses heat exchangers to warm the air coming into your house and vice versa (can't think of the correct name for it right now). Something to look into to have the best of both worlds.

[jaclaz]

>It sounds complicated but for me it just means opening windows throughout the house for about 15-30 minutes per day.

In practice what our mothers and grandmothers did, without having ever sampled air.

Some old reference:

https://news.ycombinator.com/item?id=25332981

[eastbound]

> it causes CO2 to increase because there isn’t anymore large holes to bring fresh air in

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.

[ahaucnx]

Yes, it is indeed amazing how fast CO2 levels can increase. This is especially a problem in low-ventilated classrooms.

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...

[bokohut]

Irony in the timing of your post as I too bought an air monitor filtering device a few weeks ago given my interest in measuring things I cannot see that may impact my families health. After several weeks of use and no ‘major’ concerns this past Saturday evening the air quality was hovering just below severe for many hours and the house felt 'stuffy' to me. I checked the devices readings and then asked each child and my SO independently how they felt after taking a deep breath and for generalization purposes they all stated 'stuffy' in a greatly shortened term. With a significant delta in temperature outside and in I too opened all the external doors and we had a slight wind that was then blowing through for about 5 minutes. Within seconds the air quality began to improve and after closing the house back up the air quality for the remainder of the weekend, and even now, has been optimal and everyone has felt much better. It is very interesting to measure something one can otherwise not see, such as one's air quality, and then take action to improve upon that thing which we never before quantified against how we felt which clearly has impacted our health in ways we may never know. Yet again, what you cannot see matters most!

[dilippkumar]

+1 for Airthings wave.

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.

[germinalphrase]

Open fireplace rather than a wood stove, yes?

[Maxburn]

HVAC Controls tech here;

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.

[insaneirish]

> None of this really exists in the residential sector, but maybe it should.

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...

[Syzygies]

I was blown away years ago, visiting the Anchor brewery in San Francisco. They approximated traditional steam beer in an enormous shallow pool. To improve consistency the whole room was at positive pressure, using state-of-the-art hospital air filtering.

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.

[samuraixp]

I have been getting pretty high VOC readings in my bedroom on a uHoo, Airthings and now even the Dyson HP09 shows some lower levels. So now I am confident there is something being detected. Any advice on how to debug what is causing it and what VOCs it might actually be?

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?

[criddell]

I was thinking about installing an air quality meter of some kind in my office because I suspect CO2 is high. Some of those other things (CO, PM1, etc...) may also be off.

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.

[jnxx]

> 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.

I think it has become clear that germ loads can be reduced significantly with filtering and ventilation.

[Syzygies]

Returning to college teaching mid-pandemic, I bought an SAF Aranet4 Home CO2 meter for measuring my classrooms. It mostly lives in my apartment, waiting to alert me in case I didn't realized I was using my gas range.

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.

[danuker]

> I'm lucky to ever get below 450ppm.

Considering Mauna Loa surpassed 420ppm in June 2022, I think 450 for New York City is indeed exceptional.

https://www.co2.earth/

[crazygringo]

Yes, absolutely. Probably not popular with the HN crowd, but I use the "consumer-friendly" (cloud-connected) Awair for both CO2 and PM2.5.

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.

[1letterunixname]

I took the Awair back because it was inaccurate.

[hotpotamus]

Yeah, it's another reason why I'm not super thrilled about our tendency to dump gigatons of carbon into our atmosphere.

[physicalscience]

I have several Airthings Wave connected devices, and I also purchased and installed a Panasonic ERV[0], which I have hooked into my HVAC system. Opening windows several times throughout the day was how I used to control the Co2, but in the winter and summer it became a huge hassle with the temp/humidity changes in the house, but with the ERV running 24/7 I will see an empty room drop to 400 ppm fairly quickly after people leave it (Airthings has an app). Generally rooms with people in them hover around 600-800 ppm with the ERV running. The ventilator will keep the humidity/temp levels pretty consistent because it has this cross capillary core that it runs the air through, but I do need a good few humidifiers running in the winter. The ERV also has the benefit of allowing you to control the air pressure in the house, which is useful for radon, as I was unable to get a good radon pump installed without destroying my downstairs (I live in a raised ranch where the "basement" is the first floor). With the positive pressure in my house + constant ventilation I never see the radon levels generally go above .5.

[0]: https://na.panasonic.com/us/home-and-building-solutions/vent...

[kace91]

In my country it is common to start your day by opening all windows for 5-10 minutes. It’s done several times a day sometimes.

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

[dewey]

> 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 ;)

[jonahbenton]

Running an Awair in the kitchen while cooking is enlightening. I run the stove vent fan to mitigate.

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.

[henearkr]

The radical step I took was to switch to all-electric cooking, instead of gas.

[emrvb]

Yes I measure.

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).

[dotancohen]

  > I refuse to accept indoor air quality deteriorates that much when using a proper hood

You might want to measure this. I actually think that you are correct, but what we think is often wrong.

[michaelbuckbee]

With respect to a gas stove I've felt very similarly (and still have one), but after seeing a few induction cooktops and how nice they are I'll be looking at one for our next house.

[anfractuosity]

I use a raspberry pi with both a SCD30 and MZ-14A, logging to influxdb and visualised with Grafana.

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.

* https://sensirion.com/products/catalog/SCD30/

* https://www.winsen-sensor.com/d/files/MH-Z14A.pdf

[ahaucnx]

We use the MZ, SCD as well as Senseair S8 and in my opinion all of them give a good enough accuracy. The build quality of the S8 and SCD is a lot better though. The most important thing is to stay away from eCO2 (estimated CO2) that some TVOC sensors offer which is very inaccurate.

[fuzzy2]

Wanted to do that, too, but had problems with the SCD30’s I2C peculiarities. And now the RP Zero is somewhat broken, bummer.

Next I’ll try with a Arduino ESP32 thing. The sensor was expensive, it has to work. :-D

[nsbk]

I do. I just got started because it looked like a fun project to build, I went with the Airgradient DIY solution[0]. At first I used a combination of Prometheus and Grafana, then I integrated the solution with an MQTT server and Home Assistant[1] instead.

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...

[1] https://github.com/nsbk/airgradient_mqtt

[neilv]

I stopped using my gas stove about 3 years ago, after it seemed to be causing histamine problems. It was only later that read that this was a known problem, rather than only a bizarre correlation I noticed. I now use an electric air fryer toaster oven, which causes only small particle increases.

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.

[shlant]

> after it seemed to be causing histamine problems

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.

[shapefrog]

> Do you measure

No.

> mitigate CO2 in your living space?

I open the window occasionally and when they are not open the are pretty draughty windows.

[preinheimer]

We picked up the Aranet 4. Things were fine until we replaced our windows with fancy new ones. Our air quality plummeted, CO2 > 2200.

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.

[lloydpick]

I used to monitor CO2 in the house with Awair units, specifically those because it allegedly interacted with my Ecobee AC control. So I could say if the levels were rising, force the fan on to push fresh air around, although I'm not sure I ever got it working correctly.

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.

[jnxx]

I did that in the last weeks. I live in Germany and we have a flat that is not very modern but has reasonable insulation. What I learned that under these conditions, with two people in a 30 square meters room, CO2 rises so quickly that one has to do intermittent, full ventilation (about 3 to 5 minutes, in Germany it's called "Stosslüften") for about every hour, to keep CO2 levels below 1500 ppm. During the night in a smaller room, one can get easily levels of 3000 ppm. That's not dangerous, but it is not recommended for places where people have to work in a concentrated manner, like offices, or schools, for example. The recommended limit by the federal office for environment is 1000 ppm.

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.

[qubex]

No.

(Chiming in to diminish sample bias.)

[r1ch]

I use an Aranet4 in the living room. Mechanical ventilation in most homes in NL allows configuring a precise flow rate in cubic meters so I've found the breakpoint to keep it < 1000 ppm.

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.

[arnejenssen]

I have a Nentatmo CO2 monitor in my apartment. I discovered that during training on a stationary bike, the CO2-levels exceed 1000ppm. Probably due to increased breathing. Therefore I increase the ventilation when I do a workout

[graycrow]

I'm using a relatively cheap (68EUR) TFA Dostmann AirControl Mini CO2 Meter (also available from different brands as well) based on ZyAura platform. I soldered a connector to connect it to an ESP8266 board flashed with ESPHome software [1] and then send measurements to the Home Assistant instance.

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.

1: https://esphome.io/components/sensor/zyaura.html

[j1elo]

That's the same brand I bought, after the last similar thread on HN which led me to get interested in this topic.

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.

[digitalsushi]

Modern homes are so well insulated that it sometimes happens that a family will host a big holiday party, use their fireplace for the first time, and then get dinner started shortly thereafter; the first time their nearly commercial grade overhead hood fires up, hot embers will be blown across the floor of the room with the fireplace.

(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.

[giraffe_lady]

Interesting this tracks in homes too but makes sense I guess. In restaurants the hood exhaust/ventilation system is one of if not the largest one-time cost. It's why restaurants almost always move into spaces previously occupied by restaurants, the cost to add it is usually just too much except as part of new development.