I have posted about this on HN in the past, suggesting everyone truly interested in understanding the general reality of CO2 concentration needsto buy a CO2 meter and understand the world around them first.
There's lots of good videos on the subject of proper ventilation on the "Home Performance" channel on YouTube. See https://youtube.com/@HomePerformance
I have a similar monitor and if I never open a window for days it can get up to 2000 but I feel like I can keep it at ~600 just by always leaving a window slightly cracked open (not enough to noticeably cool the apartment).
Using the stove or oven will definitely spike it though to scary levels! I've made a habit of keeping the windows fully open when I cook now.
I bought Aranet4 and it taught me a lot about how CO2 accumulates in my apartment, how and frequently to change air and so on.
The worst thing you can do is to close yourself in your room for the night. Always have either door or window open. If it is cold outside, just buy a goose down duvet. You will sleep much better in a cold room than in a warm with stuffy air.
I am looking into putting heat exchanger in my apartment so that I can change air with less energy waste.
I also changed some of my habits. I try to use less of the gas stove and more of electric grill, Instant Pot, etc. If I need to use gas then I always change air afterwards.
Hey so - closed doors are important. They stop smoke and fire from filling the bedroom giving you time to either escape or prepare to die. Sleep with your door closed and with smoke / CO (I know this is an article abt CO2) detectors.
Say what you want, I would prefer to get woken up by smoke earlier to have time to attend to my family.
My doctor is constantly asking me to do a surgery on my temporomandibular joint to prevent my teeth going out of whack constantly and my face to look better. And I am constantly telling him I would prefer to keep fixing my teeth every so often than go through an extremely invasive operation and risk possible problems.
Your smoke detectors are what should alert you of fire, not smoke getting so thick and dense that it chokes you awake... at that point you have seconds to react and live.
Yeah. I have no clue what that prior reply was about. Detectors save lives. That’s the long and short of it. One in every bedroom, hallway/basement/attic, and kitchen/living spaces doesn’t hurt.
I was co-chief of the Oral Surgery Anesthesia Division at the UCLA School of Medicine Department of Anesthesiology 1980-83.
I attended MANY (≥100) complex mandibular/maxillary/TMJ procedures intended to improve function and appearance.
Often the intended procedure — which always started at 7:30 am — had to be cut short because of time constraints.
For example: where a bone graft had been planned — using bone from the patient's hip obtained while under anesthesia — to unite intentionally fractured/repositioned bone segments, lack of time resulted in a titanium plate + screws being used instead, a less than ideal solution.
Iron Rule: Patient MUST be out of OR/in recovery room by 3 pm or dental surgeon's allotted operating time will be curtailed. NO EXCEPTIONS.
Lol I wish I could keep a window open. My apartment complex is so loud I'll get woken up. Loud music and speaker phone calls early in the morning. Actually music all hours and loose kids screaming. It's horrible.
I wonder if his apartment has gas heat and when opening the window to air it out he was causing the furnace to kick on and pump out loads more CO2? That would also explain the spikes during the cold overnight hours.
Maybe this is something to have the landlord check? In practice I don't think most gas furnaces are as well sealed as advertised. Many years ago when I lived in a house with gas heat with a dodgy pilot light I got a pretty good feel for how the thing was put together and it was absolutely not hermetically sealed.
> It's not supposed to be sealed, it's just supposed to have draft.
It depends on the model. High (>90%) efficiency, condensing furnaces are completely sealed off from the house: they take in air from the outside (via PVC pipe), combust, extract the heat, and exhaust the results (via PVC pipes).
Older lower efficiency (<85-90%) furnaces suck in air from the house, exhaust into metal pipes (PVC would melt because not as much heat is extracted from the fumes), can be back-drafted and you have to worry about CO.
Basically: if the furnace has vents in which you can see a pilot light, it's the older style.
AFAIK with gas furnaces the air touching the flame never touches the air that goes into the house, they run them past each other on top of a thin filter to exchange heat. So the CO2 produced from the flame should not affect CO2 in the house, provided the system is not malfunctioning.
I have an Airthings Wave. It does CO2 along with a couple of other things.
I really like mine. It helped me discover that I was sensitive to volatile organic compounds: every time I felt the air was stuffy inside my apartment, it corresponded to a VOC peak that was happening right then.
The one downside to the Airthings Wave is that it looks like hospital equipment. Grey, lifeless plastic pill design that was probably outdated even in the 1970s.
I'd second the Airthings device, they have pretty high quality sensors and include VOCs, CO2, pm2.5, radon, and a few others. A little bit pricey is the only downside for me.
Love mine. I think it looks fine, has a simple display to display a few values, white, and nicely rounded. Basically invisible. I use it to collect the info so I can look at the graphs as needed.
Seems like a really nice design. I was impressed that bluetooth LE was enough to connect reliably across 3 floors (with the gateway on the middle floor) of my house. The view plus automatically acts as a hub if you plug in USB for power, but falls back to batteries as needed.
All in all just about perfect, it works, easy to setup, and collects tons of data (Radon, PM2.5, CO2, Humidity, Temp, VOC, and pressure). I do wish it collected carbon monoxide though.
I have the Qingping Lite[1] which is a well-made device (and can run on batteries if you want to take it somewhere to check things out). After updating the firmware and calibrating it outside it seems pretty consistent - though I was mostly interested in it for CO2, I have a Flow 2 which doesn't agree on PM2.5 or PM10 with the Qingping, I suspect that the particulate sensor in the QP is not the best, it always seems to read low.
It works well enough and home assistant integrates with it. I cannot comment on it's accuracy since I've never owned another CO2 monitor as a reference. However, it is very responsive to the various things I've tried to manage CO2 in my bedroom - such as opening the windows to differet degrees, position of my curtains etc.
You will not be able to get something of higher value than that, because technically it's a demonstration device and likely doesn't make them much if any profit.
Maybe, but the calibration aspect to this device makes it a bit impractical.
The thing needs to be powered on and taken outside every so often for calibration, who does this for residential use I'm not sure but for most with busy lives I don't think it's a great idea.
If it is powered off at any time it needs to be done again if I'm not mistaken.
They will apparently include calibration options in the next firmware update.
And it's not as much as of a hassle as first appears. After a week you can expect readings to drift downward by 50-200 ppm depending on whether or not you aired out the room at all - and it's a one time thing, won't happen continuously every week. Then you just take it outside and it will be fixed in under 10 minutes (<400 ppm reading trigger auto calibration immediately).
I'm not confident that the other co2 meter options are in any way better. They most likely also do auto calibration but don't tell you. Counting on the fact that most people won't notice the drift.
I have an Aranet 4, mostly able to keep things around 600 with a little bit of ventilation.
It goes up when we're together in a small room with no door open, I'm planning on eventually retrofitting MVHR which should help improve indoor air quality and allow me to insulate.
In the meantime the Aranet is good for getting a handle on general air quality and how you can improve it.
If you want to DIY it, Aranet4 uses a Senseair Sunrise which can be had for 1/4 of the price on Digikey [0]. Senseair has Arduino samples on GitHub [1].
I personally have an SCD30 monitor which claims the same accuracy and like it. The important thing is to calibrate them in outside air to 400ppm.
you can do so, and properly calibrate it, and cross check it with some "known good" sensor you lend yourself from a friend and make sure you get the heat sensitivity of sensor and stuff like that right etc.
most people can't, or more precise they probably can put something together but can't make sure it works correctly under any situation (in operation range)
what you pay for is that someone makes sure it works properly
else you can get sensors with similar or same hardware on amazon too, it's just that their correct reliability is not guaranteed at all and just checking if the values outside seem right is by far not enough to verify that (because it e.g. might behave right on low but not high CO2 levels or not on high/low humidity, etc.)
You generally don't have to go to all that effort unless you want extreme accuracy. For "Good enough", you buy the sensor, follow the application notes and instructions from the manufacturer, calibrate it in fresh outdoor air and you're good to go.
I have seen tests with sensing devices which seemingly where good outside but then e.g. scaled wrongly being way of at higher CO2 levels (either way higher or way lower).
Can you provide a citation? I live in a city center Warsaw, and co2 outside is similar to anywhere else - around 420-450 max at all times. Perhaps it's due to a good city design with multiple open spaces though.
... tldr a higher planetary boundary layer over cities can form under various weather conditions. That reduces mixing, and cities are large sources of CO2.
Thanks for this! I very much do want to DIY it, but lacking the time and my 9-year-old looking for a circuit python project, this might just fit the bill.
We maintain a popular open hardware air quality monitor that also uses a Senseair CO2 Sensor [1]. This gives you a lot of flexibility on how to use the data.
The pre-soldered version is easy to build and also includes a PM sensor.
Pricing out the parts buying third party and there's very little savings in doing so due to the cost of enclosure and the pbc especially the additional 24 to $30 shipping.
I'm wanting a Co2 monitor that works without cloud and looked at some of the sensors available.
Does the sensor in your project need to be taken outside to calibrate?
I stopped when I realised many sensors (like scd30/40) need this making it very impractical.. Has to be done once while powered on the whole time in a 7 day period.
I think pretty much all indoor air quality monitors with NDIR sensors have by default an automatic baseline calibration. Our kicks in every 7 days. So you should somehow reach ambient CO2 levels once a week to have it properly calibrated.
I don’t enable automatic calibration on my SCD30 because the algorithm basically assumes that the lowest ppm in the last 7 days is 400ppm and baselines to that. I just took mine outside once, set that to 400ppm and haven’t recalibrated it since. The drift on the sensor is supposed to be very low.
The SCD41 is a very different sensor. The Senseair Sunrise requires through-hole assembly, uses a low-power version of NDIR and is relatively bulky. The SCD41 requires surface mount assembly, uses a higher-power proprietary technology based on MEMS and is very compact for a CO2 sensor.
Personally I've been very happy with Sensirion's sensors and I've played with the SCD41 quite a bit. The trouble with it for hobbyists is the assembly. It has what seems to me to be pretty picky requirements for soldering. I've attempted to do it myself but I keep managing to pop off the metal covering.
Haven't tried the Senseair Sunrise but such low power requirements are very very appealing because they mean the sensor can be battery-powered. The SCD41 isn't bad but powering it for a year means a lot more batteries. With a 1 min sampling period, the SCD41 uses 1.5mA while the Sunrise uses 21µA.
I think they're around 60 bucks (e.g. the T6793) so they aren't the cheapest around, but they're good quality.
They have a normal header you can solder a few wires into. Probably the best approach for the Sensirion sensor is to oversize the pads a bit and use paste to re-flow underneath.
I have quite a few of the older T6613/T6615 sensors that I got when Newark was selling them for like $10 a piece.
The way I soldered the SCD41 is with a pre-made PCB footprint, some solder paste and a mini PCB heater. I think the problem was too high heat. I need to try it again with low-temperature solder paste.
But for my application the Senseair Sunrise looks a lot better.
How accurate is it in term of linearity of calibration, and how much does it drift over time?
As a diver I use oxygen sensors, and those should be calibrated once every third day, and linearity can go bad from everything between 6 months to a few years.
If I went with a DIY solution i would definitively go with 3 sensors so one can at least use voting to determine which sensors to trust, and to measure relative drift.
Out of curiosity what voting mechanism would you use? Obviously consensus would be solid for something binary but for a ~continuous value like CO2 level I'm not sure what would make the most sense.
One method used in one of my diving equipment is to take one sensor and compare the value to the average to the other sensors, and if it's too far out, mark it as potentially broken. Cycle to next one and repeat.
This can still situation where either a bad sensor is marked as good, or a good sensor marked as bad, so a human operator is still required to monitor the decisions made.
In 2020 I bought a Netatmo CO2 sensor, since it was cheaper than the alternatives. Not sure how accurate it was, but it seemed accurate enough (450-500 outside).
Live in the PNW with only electric heating/stove/oven. Cracking the window very slightly was enough to keep CO2 relatively low (600-800). Had to crack the window more when the temp is around 70 outside, less when the temp delta is higher (cold or warm).
Eventually ditched the device once I understood how to keep CO2 low. The cloud integration was creepy. I could tell when my wife or I went to bed based on CO2 spiking near the sensor.
A potential alternative for haters of the cloud: I got an Airthings Wave+ unit. Home Assistant can immediately connect to it via Bluetooth LE and get readings. It'll be auto detected if it's within range when you put the batteries in, assuming your HA install has Bluetooth support (mine worked out of the box with a Pi 3B.)
(Specifically the Wave+ though; the hub apparently will want to connect over wifi instead, so I think it's better to just go for the Wave.)
i have massive conflict with co2 monitoring, just like this article. I have monitored my air for years, mostly for PM levels from fires but co2 came with it. I became obsessed with lowering the co2 at the expense of cold temperatures, but I have never noticed a "cognitive" difference between 2k ppm and outside. instead I just feel physical unrest with seeing the high number, like I am suffocating on this "clearly bad air". Yet I am certain if I was completely unaware of it I would have no issues. Any time friends come over and it's winter, ppm in an apartment would be 2500+ and nobody cares
I can tell. I’m thinking there is a lot of individual variance for co2 tolerance. I can feel 800+ ppm and after i have had the sensor a while can tell what the concentration is within 25% or so without looking. I also feel the cognitive effects, and moreso the positive effects of opening a window.
Different places I’ve loved have had significantly different characteristics for what co2 concentration defaults to.
I’m guessing a not so small proportion of mental health issues and things like chronic fatigue are actually breathing issues and sensitivity to higher co2 concentrations.
For me a big factor is I broke my nose long ago and don’t breathe as well as I should.
If you can, you should try a "blind" test outside your home sometime. i.e. Bring the monitor to a hotel room for your next stay, try to guess it, and then see what the actual number is.
right, CO₂ has become a (inter-)national psychosomatic obsession of the privileged class, but no one should be worrying about CO₂ at all, unless you work in some very specific industries. you'd need a ppm of 50,000-100,000 to feel any real effect from CO₂, or to see noticeable greenhouse effects from it. it's today's equivalent of fearing power lines or MMR vaccines. it's fretting on something that feels tangible and controllable, without delving deeper and examining the (social and mass) media-driven presumptions underlying those fears.
pollution, on the other hand, is a real concern. that's stuff like radon, VOCs, methane, dioxins, and SOₓ emissions. as such, one thing we should be doing with vigor and relentless focus is phasing out coal plants (if we were actually putting our priorities in the right place) rather than worrying about the sideshow that is carbon emissions.
nope, that's exactly right. at 5-10% you feel real effects, not at 1200ppm or 3000 or any other psychosomatic level.
"poisoning" is a needlessly loaded word in this context. CO₂ is literally critical for life. just about any molecule/compound at those concentration levels (outside of those we co-evolved with, like nitrogen) will have noticeable effects as well.
There was a video I watched years ago where someone was on an airplane and basically tested how they'd react with a lack of oxygen. It was pretty crazy. He knew he needed oxygen, but didn't feel like he needed to do anything about it.
I wonder if it's something you're more likely to notice in hindsight (and not at all if it's subtle). I was recently hypoxic (~78% SpO2) due to COVID-19, and felt absolutely fine at the time, but looking back, I was making some questionable decisions (waiting three hours after reaching 80% on a pulse oximeter before seeking any help) and my memory until I was placed on oxygen is pretty fragmented.
I had an attack of viral epiglottitis approximately 18 months ago and called 999 as I could feel my throat closing up. When the ambulance crew arrived they put a pulse oximeter on me, and my heart rate was above 130 and remained so even after sitting on the sofa for 10 minutes trying to breathe normally. SpO2 kept declining no matter how hard I tried to breathe, and they took me down to the ambulance and intubated me just as my fingertips started to turn blue.
I was lucky enough to avoid intubation, but I suspect I wasn't too far away from it. CPAP with pure O2/a high-flow nasal canula at 90L/min pure O2 (I initially couldn't tolerate the CPAP mask for extended periods due to an anxiety disorder, though I felt myself becoming more fatigued over time on the HFNC) was keeping me at 88-90% (arterial blood gas measurement) initially, and that slowly started to climb a few days into treatment.
The idea that indoors air can be hazardous is an old idea, and predates CO2 monitors and gas stoves. Following the 1918 Influenza Pandemic (aka Spanish Flu), apartments in NYC were built with absurdly large heaters so that residents could be comfortable while all the windows were open [0]. There's also the German practice of lüften [1], or ventilating a home at least once per day; and the Scandinavian idea of having babies nap outside [2].
I have a Hydrofarm Autopilot CO2 monitor and it pretty much stays at 600-800 all day, but I leave a window cracked open and live in a naturally windy area.
Especially “Stoßlüften” (opening a window for a short period) or “Querlüften” (opening windows in opposite rooms to create a draft).
First thing in the morning we lüft, after cooking, we lüft, before going to bed…
It’s especially important in newer or well renovated houses/apartments, to get rid of excess humidity in order to prevent mold. Really new apartments are so well insulated that they have literal holes in the wall (Zwangsbelüftung) in order have some airflow.
Edit: I was so enthusiastic to write a comment about lüften, that I didn’t read your link which actually covers what I said.
Does it not depend on the windows, though? My contract in a new place does not require me to open windows several times a day anymore. The windows seem to have a built in mechanism, that allows for air exchange. I can even feel a cool breeze sometimes, so something is definitly going on, though very subtle.
I see your landlord is worried about your health too. Mine is very thoughtful. In addition to poorly jointed windows so the air stay fresh, they are single panned so it doesn’t get too hot at night and we can get optimal sleep.
No, more like the guy who designs how the airflow in your home should work, without opening any windows. Making sure you get a balance of enough clean air coming in, plus making sure you have the right amount of humidity control, and the right amount of exhaust of air containing too many contaminants, plus the right amount of heating and cooling, and everything else.
I wonder if plants are similar (negligible effect on air) in room scale. I have about 10 small plants in my apt. I would like to think they're scrubbing the air.
Indoor plants give virtually nothing in terms of scrubbing co2. An average human breathes out around 1kg co2 per day. The plants would need to take up 1-2kg in mass to have a measurable effect. That would require a small rainforest at home.
If I remember correctly, there were some studies that calculated you'd need to convert half of your room into a dense jungle to offset your own co2.
Also, plants release co2 at night, so even if they had any effect, it would be a bad idea to have them in bedroom to scrub air.
> There's also the German practice of lüften [1], or ventilating a home at least once per day
Meanwhile, in Latvia there's a belief that "caurvējš" (drafts) are bad for you and that you'll catch a cold if you're in it for too long.
I've read some arguments for and against that online (mentions of cold stress, muscles posssibly tensing up to remain warm leading to a stiff neck, possibly nose being a bit more dry and susceptible to things in the air), but people over here typically just accept it as "fact". I can kind of understand caution when it's -10 C outside, but less so when you're in a stuffy room and it's 20 C outside.
Curiously, people in some other countries don't have such strongly held beliefs.
My mother used to complain about neck pain from drafts (the vent in the car primarily), now I get it too. It's like a milder form of the pain that follows a cramp. Maybe it's genetic?
I've lived in six countries, and old people everywhere want to keep their joints warm.
I have the issue where we love a cold house but my hands don't, at least when I work, so the house is very cold, 14ºC/57º at night or even less, I get up wearing very little and make coffee in a chilly kitchen with pleasure, but then go to work in my shorts right beside a heater.
There's not necessarily a conflict in these views though - short drafts are good to ensure ventilation, but long, continuous drafts are just plainly uncomfortable.
My old college dorm was like this, where the radiators would make it so hot you absolutely had to open the windows and even run a fan in the Massachusetts winter. Never occurred to me that maybe it was on purpose.
Sure; modern gas stoves are nothing compared to the coal- or wood-fueled stoves of the old, with their often ineffective and obviously unpowered exhaust mechanisms. Merely a hundred years ago, even in my wealthy Western country, many people lived in huts with only an opening in the ceiling for a chimney.
And of course billions of people live like this right now, domestic coal or kerosene burners being one of the most pressing air quality issues in the world!
I think so too. Use to work with a lot of CO2 sensors in a previous job and it's very difficult to keep an elevated CO2 level going if there's any exchange of air with the outside.
But in a larger apartment or house it could mean that if you occupy one room, like the bedroom, you get air with less CO2 from other rooms. If you have no ventilation on and no airflow, it must be worse.
Doesn't seem to matter: running just the fans alone is enough to lower CO2 readings in my house. I suspect the main reason is just diffusion of concentrations of CO2.
potentially, the air volume of a room hugely affects how often you have to air the room (but can also making the airing take longer depending on window size, arrangement, wind, etc.)
one of the reasons some people swear on living in houses build around 1900 where I live, the larger ceiling height adds air volume (there are other reasons like large windows, wooden floors, etc.).
Seems like we're forgetting that the objective is not to reduce CO2, it's to reduce the pathogens in the air.
Since it's difficult to measure pathogens directly, we use CO2 concentrations as a proxy, since high CO2 means poor ventilation which means potentially high pathogens.
It does matter for sure. At least in a modern/energy-efficient "tight" (as in, airtight) build.
You can be right that turning on circulation makes the number go down. But that doesnt matter. Over time the concentration can go up and up and up, even with h"v"ac running.
Few residential HVAC systems actually ventilate. The focus on energy-efficiency has been a bit blind to the need to get rid of od co2 & take in oxygen. You can get fancy energy-recovery ventilation (ERV) devices that actually do air-exchange with thermal coupling, to cool or heat the incoming air. But this sort of system is alas exceptionally rare.
I installed a broan nutone ERV this past summer and it's made a tremendous difference with the CO2 levels in my house. We retrofit spray foamed the house (don't, dumb idea, definitely not the attic if you're reading this) and CO2 would build up in the nursery over night well past 1400ppm according to an AirThings Wave+. Now at night it averages like 800ppm in there.
With an ERV, the best thing that I found to do is wire it to my furnace such that when the furnace kicks on, it will trigger the ERV to start. Otherwise you'll get furnace blower cycles separate from ERV cycles and it won't be as effective.
Seconding the large impact of an ERV, the air inside feels much fresher when it's on vs when it's unplugged.
I've taken to just running the HVAC fan at all times, regardless of whether heating/cooling is happening. This tends to even out the temperature throughout the house, as well as CO2 concentration, it keeps the air filtering through the HVAC HEPA filter, and the ERV can run continuously, so rooms rarely get above 600 ppm CO2. Unsure about the energy use impact, but the air quality difference is palpable.
> We retrofit spray foamed the house (don't, dumb idea, definitely not the attic if you're reading this)
Can you elaborate? We are considering moving into an older house and renovating. Adding insulation being part of the idea. Our current home has full foam insulation with erv so I am curious what difference you experienced.
First the off-gassing. It emits a lot of harmful compounds as it cures and I understand the emissions to go on for a long time. So if you mind about air quality it wouldn't be my choice.
Second is the potential for damp to build up in the building fabric. The foam is airtight so make sure the ventilation is right on both sides of it.
A bonus third is the pain of removing it when you need to do building repairs. With board or batts you can lift them out; with spray foam you have to cut then scrape off.
Which is, by the way, insane. Aside from freshness reasons, I live in a mild climate and it's not an infrequent occurrence for outside air to be closer to my target temperature than inside air.
Even if you're referring to a HVAC with an entirely internal airflow, this isn't necessarily correct. For a long time I used the fan mode of my ducted AC to distribute air around my house, which dramatically reduced the level of bedroom CO2 concentration while asleep from well above 1500 ppm to below 800 ppm.
Am I reading this wrong, or does the author really keep mentioning "attempts" at things that will do absolutely nothing to CO2 levels? Non-venting range hood? Box fan with filter? These will do nothing for CO2.
The only way you're going to bring down CO2 levels in your dwelling is to bring in outside air. The best way would be installing a heat recovery vent that will save some energy. The simple way would be to open two windows and stick the fan in one for a short time (blowing in for turbulence to clear out the corners of the room).
Leaving your windows open with passive circulation for a longer time is going to cool down all the stuff inside, wasting much more heat.
The article is a little mixed up, but the author does seem to understand this. I don't think the author knows she needs to try and set up distinct air intakes and outputs with her windows and fans.
I've had a few CO2 meters, and learned not to trust any <$100 as they don't really work. I look for meters that use non-dispersive infrared diffusion sensors (NDIRs), like the Aranet4. I've found the TIM10 desktop model from co2meter.com to be accurate (AFAICT), uses NDIRs, and only US$139.
I also have other air quality meters. (I collect measuring devices.) I wish there was a do-it-all air meter.
Do you know if the Aranet4 can be used over bluetooth/wifi without internet access? I've been looking at a bunch of devices and haven't seen aranet yet.
Also, have you ever put all of your devices near each other to compare the variance between them all?
I got my Aranet4 because it had very good reviews and allowed local read out of sensor data without any "cloud" involvement. I've been very happy with it, the readings are integrated into my Home Assistant setup so automations can respond to high CO2 (e.g. turn on a fan directed at a window, when temperatures are high enough to have a window open).
I have a TIM10 that was once reporting negative CO2 levels one spring with the windows open. I'm not sure what I think about it. It's not a scam product by any means, it can definitely tell when someone is in the room or a window is opened or closed. I needed the space and unplugged it awhile ago and just don't worry about CO2 levels currently.
My understanding is that some co2 sensors assume the minimum value seen over the last 30 days is 400ppm as a calibration. This could possibly explain a negative value if the sensor has been in higher co2 environment for some time, and is suddenly exposed to the outside.
"In a study at Naresuan University, Phitsanulok, Thailand, the snake plant can absorb CO2 at 0.49 ppm/m3 in the closed system."
That would require an enormous number of snake plants to do anything. A tiny apartment is 50m^2 * 3m = 150 cubic meters, so it requires 300 snake plants just to bring down by 1ppm (though not sure over what timescale or other assumptions in the work cited)
Because you need to take time into account and it's more coherent with the result of other studies (an optimist case with good sunlight but 0.4ppm/m3/m is ok I guess for young plant).
yeah I'm not sure what the timebase is but I wondered that myself. I assumed it was per hour or day, but not an expert in plant biology and my assumption sounds like it was wrong.
'The approximate amount of carbon exhaled by a single human in 1 d is 300 g, whereas the carbon content of 1 L of gasoline is 640 g. In comparison, a single Spathiphyllum in a 15-cm pot grown at a PPF of 20 mmolm–2s–1 fixed 0.8 g C per day, so it would take 400 plants to offset a single human or 845 plants to offset a gasoline use of 1 Ld–1.'
What person does a back of the envelope calculation and manages to equate 75kg of metabolic tissue consuming around about 0.8kg of oxygen a day is going to be cancelled out by a couple plants draped around the place?
What's wrong with having hundreds of plants then? Filtration doesn't get rid of CO2, opening the windows just brings your CO2 levels to whatever it is outside (at best).
Planting more plants is at least a step in the right direction. Everything else is more or less simply turning it into someone else's problem.
Just the practical component.
If you’re in a closed environment, and you want to reverse your CO2 production, you need to create new biomass roughly equivalent to the quantity of food you consumed that day. The practical consideration that is totally skipped on the question renders the inquiry useless for any practical purposes for most humans
Not the whole biomass. Just the mass of CO2 that falls into the category of "collects in your house when the windows are all closed". I'm not going to argue that it's a small number nor that it's easy to take care of a large array of plants. It's just that everything else short of using plants seems like a simple offloading of CO2 elsewhere (e.g. opening windows). I'm not satisfied with such selfish solutions.
You're right that the practical consideration is important. It needs to be addressed and engineered to be made practical.
On top of that maybe we eat too much, but that's a off topic.
It's a bit weird to me that people get a sensor and then worry about the air. What are the symptoms of elevated CO2 levels? Why can't you feel them and need a monitor to tell you you are unwell?
The most convincing evidence is from the ISS: at 5000ppm CO2, the crew experienced "headaches, lethargy, mental slowness, emotional irritation, and sleep disruption." - so you can feel too high a CO2 level and open a window (if you know to consider that as a problem which causes these symptoms).
The studies suggesting 1000ppm may be harmful are called out in the wiki article and it seems the jury is still out as to if the effects are real/are the result of CO2 and not confounding issues.
Sorry, I should have been clearer. I understand that there are harmful effects you can feel at very high concentrations, but it's weird to me that some people (like the author) are freaking out over concentrations they can't feel.
Well... People aren't rational. Or particularly good self-observers. For any given concern, there's going to be a group worried too little and a group worried too much.
Some people are more sensitive than the others. Also, if you haven't experienced living in a well ventilated home, you may not realise you feel it - you may think that going outside is good because sun and movement, and not because you finally get fresh air.
Sometimes I have no trouble concentrating and getting great work done, while other times I feel stupid and my brain doesn't work. I would like to spend more time in the first category and less in the second. Noticing that I feel unwell is very easy, but is only useful if I know _why_. CO2 levels are one of many things which could cause this, so I bought a CO2 monitor to find out if they're correlated, and if so I had the idea that I could get alerts to remind me to open a window before it became a problem.
Were they correlated? Did you regularly think "I'm feeling stupid" and glanced at the meter and it was elevated? Conversely, did you look at a low reading and notice that you had no trouble concentrating?
Even on healthy apartments it's common that you have to air them 3 (maybe 4) times a day for around 30min each to have low CO2 levels (assuming you spend the whole day indoors in a single room apartment with not too much air volume, no kitchen usage or separate kitchen you have the door closed to, etc.).
Most people I know don't air out their room/apartment long enough and/or often enough.
And I have been thinking about getting some form of huge fan to speed up the airing exchange process in winter.
> Even on healthy apartments it's common that you have to air them 3 (maybe 4) times a day for around 30min each to have low CO2 levels.
Would it work to just open small openings on opposite sides of the apartment and put a small fan on one and run it continuously? With the right fan speed that should be equivalent to the big 30 minute airing ever few hours, but I'd expect it would be less disruptive when it comes to comfort because it should result in much less temperature variation.
In the end it's all a matter of how much air is exchanged if air from everywhere inside is at least somewhat affected and how high/low the outside CO2 levels are.
E.g. if you have a apartment in the 5th floor where always have a bit of wind and can open windows so that the wind flows through just opening it for 5min might have as much effect as other people get with 40min.
Or e.g. if you have the right kind of wind putting windows into tilting mode can work well and in other cases (like my apartment) you will leak heat with very little air exchange.
I have been thinking about using some sort of fan but haven't tried it out. Part of the reason is that in summer I just can keep the window open all the time and currently we have winter temperatures around 4-7C during the day and my room temperature is most times around 16C in winter anyway, so ... it's not too much of a heating problem (compared to people heating their room to 20+C).
I had the opposite experience. Bought an AirThings and it made it clear that co2 gets high with windows closed and the heat on.
We live in a nice suburb near the water so outside air is clean. I now crack the windows open and co2 stays reasonable. I feel much better.
Before this, I was anal about insulation and making sure windows were closed when the heat was on. Now I know that's not the right calculus.
I could have figured out that I feel worse in the winter at home and feel good the moment I step outside. But having the numbers shown to me really drove a change in behavior
I had a somewhat similar experience. However, before living in an area with clean air in a house, I previously lived in apartments and was well aware that the CO2 (and PM2.5) levels were unideally high. I feel like the author should maybe ask a medical professional about anxiety, unless they're just being a bit melodramatic.
With perfect insulation theoretically you need to put in a lot of additional care to make sure the air in an apartment stays right (and fungi doesn't start growing, etc.).
This include some system for automatic air exchange (which also keeps the heat in and isn't prone to fungi and isn't loud/distracting and doesn't draw a lot of energy; not easy to get right at all).
Guess what basically is non existing in close to all modern apartments I have seen...
Instead they tell you you have to "appropriately" air you apartment and skipping over the fact that this might mean 3 times a day 30min no matter what temperature is outside (on dais you stay home all day).
30min is excessive and counterproductive because it will cool down your home too much.
around 5 minutes with windows fully open and heating closed will do the trick. You want to maximize air exchange while minimizing heat loss.
This is common wisdom in Germany but the rest of the world seems to either prefer to heat the outside air instead of insulating their houses or must live in very sticky rooms. I just can't imagine not ventilating a room regularly.
> around 5 minutes with windows fully open and heating closed will do the trick.
no it won't not at all it's a common misconception especially in Germany
EDIT: jut to be clear it does work if you do the 5m airing often enough, but this is where the problem comes in it is fundamentally unpractical. I mean I can measure it tomorrow (through after long airing after sleep).
most ideas about insulation circulating in Germany are only half thought thru and sometimes do more environmental harm then good (depending on the building).
I just checked it this morning and I would need to do it around ~15 times a day, additionally a longer 20-40min airing in the morning.
So 55m no airing then 5min airing.
That's not at all something viable with home office, too disruptive.
Now if I would be fine with having it constantly roughly between 1000ppm and 1400ppm then I could air it out much less often (because the higher the difference outside/inside is the less volume of fresh air you need to let in to make it drop the same absolute amount).
> I just checked it this morning and I would need to do it around ~15 times a day, additionally a longer 20-40min airing in the morning.
I can't really follow how you checked and were able to come up with these number from apparently one single measurement?
I still think the main issue is that you are not airing properly. The best way is is to create a draft situation by opening windows that are across from each other. If you can open the front door, even better. Again, you need to FULLY open windows, no in between state. Like fully open. If you don't have to remove the plants from the window still, you are doing it wrong. Having windows half-open will do barely anything for air circulation.
If you are not able to sharply drop the CO2 in a few minutes, there might be something else going one that you haven't mentioned. Maybe a HVAC system like another commenter suggested.
> Now if I would be fine with having it constantly roughly between 1000ppm and 1400ppm then I could air it out much less often (because the higher the difference outside/inside is the less volume of fresh air you need to let in to make it drop the same absolute amount).
I mostly use 1.2-1.5k ppm as a signal that it is time to air again. Obviously it is not realistic to never go above 1k ppm and that is fine. Long term exposure might make you slightly sleepy but a few hours of it are probably fine.
So I guess the 15 times would kind of check out if you wanted to keep the CO2 constantly low but that would be indeed excessive.
I think you fail to realize air flow situations of various apartments can _massively_ differ due to factors fully outside of the control of the people living there.
I had done measurements in the past and just doubled checked if I remembered correctly and how a 55m wait 5m airing cycle would work by doing it for the first 6 or so hours of my day.
> I mostly use 1.2-1.5k ppm as a signal that it is time to air again.
The think is if I as much as reasonable possible air out my apartment for 5min when it hit 1200ppm it e.g. just now went down to around 1000ppm...
And yes the airing situation in my apartment is not optimal, but that is with what I meant a lot of German "common knowledge" and (worse) regulations are often not fully thought through. It's based on the "how it should be" situation and blindly applied instead of how it actually is. And a lot of apartments in Germany have sub-par airing conditions in Germany, including worse then mine.
>This is common wisdom in Germany but the rest of the world ...
In Italy, the tradition has always been that when you wake up in the morning you open windows and let the air change, but the "new generations" are forgetting this, just when houses are built (or refitted) in a much more airtight way.
The only way out, mechanical ventilation systems, possibly with a heat exchanger[0]), are still rare, even in new constructions, I have seen a lot of issues in the houses built with (badly designed) energy saving goals (original A and B classes) built or renovated in the last 15 years or so.
[0] which bring their own issues, needed maintenance, periodical cleaning of filters, sometimes noise, etc.
No longer living in an apartment but - cracking the windows a bit seems fine. Your heating system might work harder to keep up so costs more and it's up to you to determine where your price/temperature/air quality sweet spot is.
It's not the most efficient but I second keeping the windows cracked open, in some buildings heating can't be turned off and gets the room too hot anyway so you get fresh air and regulate the heat too.
I recently bought an CO2 monitor and it was a very good decision.
I was shocked to see how fast CO2 will build up in just a few hours. Specifically online meetings when I do a lot of talking seem to drive it up.
That said, opening windows will drive the CO2 down to 500ppm in a few minutes. I think the OP does not know how to properly ventilate a room. You need to completely open the window or even multiple windows. They probably just had it half-open which will waste energy.
Also, if you look at the actual limits, no 1.2k ppm is not horrible. It will regularly reach 1.5k or more for me. Prolonged exposure of that can make you a bit sleepy but there is not reason to panic.
So, ventilate a few times a day properly. Don't just have the windows open all the day or the heating bill will kill you.
// They probably just had it half-open which will waste energy.
Can you explain that? I recently started to leave the window open 1-5 inches and it's done a good job, I am curious why half opening a window is problematic.
The ideal situation is that you exchange all your inside air in as small timespan as possible. Air doesn't hold that much heat, so your walls, furniture and other mass retains their heat. The new fresh air gets heated up relatively fast.
So you want maximum airflow for a short time. Best way is to fully open windows on different sides of the house and hope that creates the flow.
Very common method in Germany, they call it Stoßlüftung.
I don’t worry about heating in the winter, but I do worry about cooling in the summer. When it’s 102F/38C outside, my AC can barely hold 76F/24C inside. If I open a window for 5 minutes, I get a blast of hot air that will result in my AC running for hours. On a hot day, the indoor temperature probably won’t drop until overnight.
Well sounds like you're from a warmer climate, so makes sense if the European methods do not apply.
I have exactly the opposite problem from you. I don't even have AC, plus I'm comfortable at 82F/28C inside so I can keep the windows open all summer. In winter on the other hand, "keeping the window cracked open" like people have commented is definitely not an option. All modern buildings have mechanized ventilation systems for managing this but I live in an old apartment without ventilation, so a large airflow for short periods seems to be the best approach to get fresh air without losing the precious heat.
Because thermal energy doesn't necessarily move the way air does. Very much like a closed loop water cooler for a PC: the water in the loop is the same, but the heat is gathered up and dispersed once it gets to a place it can be emitted/removed.
I am using a WYND Halo air quality monitor, which was a Kickstarter. It monitors CO2 and other pollutants like VOC, even shows the particle size. Temperature, humidity and light intensity are also tracked. The app shows charts, but I haven't figured out how to download the data.
The Halo can also control an air purifier, which has been really handy. It's pretty cool to see the air quality improve while the purifier does its thing. This was especially important when we had horrible air quality due to forest fires.
Edit: The app actually let's me export all data as CSV.
383 comments
[ 2.8 ms ] story [ 314 ms ] threadUsing the stove or oven will definitely spike it though to scary levels! I've made a habit of keeping the windows fully open when I cook now.
The worst thing you can do is to close yourself in your room for the night. Always have either door or window open. If it is cold outside, just buy a goose down duvet. You will sleep much better in a cold room than in a warm with stuffy air.
I am looking into putting heat exchanger in my apartment so that I can change air with less energy waste.
I also changed some of my habits. I try to use less of the gas stove and more of electric grill, Instant Pot, etc. If I need to use gas then I always change air afterwards.
Source: am firefighter, sleeps in bedroom.
I'm not sure why it's such a problem to have a possible 15% cognitive decline while I'm sleeping. I'm already an idiot in my dreams.
My doctor is constantly asking me to do a surgery on my temporomandibular joint to prevent my teeth going out of whack constantly and my face to look better. And I am constantly telling him I would prefer to keep fixing my teeth every so often than go through an extremely invasive operation and risk possible problems.
Source: retired anesthesiologist (38 years).
I was co-chief of the Oral Surgery Anesthesia Division at the UCLA School of Medicine Department of Anesthesiology 1980-83.
I attended MANY (≥100) complex mandibular/maxillary/TMJ procedures intended to improve function and appearance.
Often the intended procedure — which always started at 7:30 am — had to be cut short because of time constraints.
For example: where a bone graft had been planned — using bone from the patient's hip obtained while under anesthesia — to unite intentionally fractured/repositioned bone segments, lack of time resulted in a titanium plate + screws being used instead, a less than ideal solution.
Iron Rule: Patient MUST be out of OR/in recovery room by 3 pm or dental surgeon's allotted operating time will be curtailed. NO EXCEPTIONS.
It depends on the model. High (>90%) efficiency, condensing furnaces are completely sealed off from the house: they take in air from the outside (via PVC pipe), combust, extract the heat, and exhaust the results (via PVC pipes).
* https://www.youtube.com/watch?v=lBVvnDfW2Xo
Older lower efficiency (<85-90%) furnaces suck in air from the house, exhaust into metal pipes (PVC would melt because not as much heat is extracted from the fumes), can be back-drafted and you have to worry about CO.
Basically: if the furnace has vents in which you can see a pilot light, it's the older style.
I really like mine. It helped me discover that I was sensitive to volatile organic compounds: every time I felt the air was stuffy inside my apartment, it corresponded to a VOC peak that was happening right then.
The one downside to the Airthings Wave is that it looks like hospital equipment. Grey, lifeless plastic pill design that was probably outdated even in the 1970s.
If you ignore how it looks, it works fantastic.
Seems like a really nice design. I was impressed that bluetooth LE was enough to connect reliably across 3 floors (with the gateway on the middle floor) of my house. The view plus automatically acts as a hub if you plug in USB for power, but falls back to batteries as needed.
All in all just about perfect, it works, easy to setup, and collects tons of data (Radon, PM2.5, CO2, Humidity, Temp, VOC, and pressure). I do wish it collected carbon monoxide though.
1: https://breathesafeair.com/qingping-air-monitor-lite-review/
It works well enough and home assistant integrates with it. I cannot comment on it's accuracy since I've never owned another CO2 monitor as a reference. However, it is very responsive to the various things I've tried to manage CO2 in my bedroom - such as opening the windows to differet degrees, position of my curtains etc.
You will not be able to get something of higher value than that, because technically it's a demonstration device and likely doesn't make them much if any profit.
The thing needs to be powered on and taken outside every so often for calibration, who does this for residential use I'm not sure but for most with busy lives I don't think it's a great idea.
If it is powered off at any time it needs to be done again if I'm not mistaken.
And it's not as much as of a hassle as first appears. After a week you can expect readings to drift downward by 50-200 ppm depending on whether or not you aired out the room at all - and it's a one time thing, won't happen continuously every week. Then you just take it outside and it will be fixed in under 10 minutes (<400 ppm reading trigger auto calibration immediately).
I'm not confident that the other co2 meter options are in any way better. They most likely also do auto calibration but don't tell you. Counting on the fact that most people won't notice the drift.
It goes up when we're together in a small room with no door open, I'm planning on eventually retrofitting MVHR which should help improve indoor air quality and allow me to insulate.
In the meantime the Aranet is good for getting a handle on general air quality and how you can improve it.
I personally have an SCD30 monitor which claims the same accuracy and like it. The important thing is to calibrate them in outside air to 400ppm.
[0] https://www.digikey.com/en/products/detail/senseair/006-0-00...
[1] https://github.com/Senseair-AB/Sunrise-Examples---Arduino
I could even send levels to my home IOT InfluxDB for historical charting.
most people can't, or more precise they probably can put something together but can't make sure it works correctly under any situation (in operation range)
what you pay for is that someone makes sure it works properly
else you can get sensors with similar or same hardware on amazon too, it's just that their correct reliability is not guaranteed at all and just checking if the values outside seem right is by far not enough to verify that (because it e.g. might behave right on low but not high CO2 levels or not on high/low humidity, etc.)
I have seen tests with sensing devices which seemingly where good outside but then e.g. scaled wrongly being way of at higher CO2 levels (either way higher or way lower).
Perhaps you've left the auto calibration on? That's usually a recipe for disaster (and one that can be avoided by reading the datasheet).
This includes all the sensors integrated in these off the shelf products like the author is using, which could explain the extremely high readings.
The outside ppm changes quite a bit in cities. CO2 dome effects can push it 2x higher.
https://www.researchgate.net/figure/The-maps-of-global-histo...
Older study https://www.sciencedirect.com/science/article/abs/pii/S13522...
... tldr a higher planetary boundary layer over cities can form under various weather conditions. That reduces mixing, and cities are large sources of CO2.
So I can say - I stand corrected, and TIL :)
Anywhere that traps smog should show similar correlations with CO2.
[1] https://www.airgradient.com/open-airgradient/kits/
So far people that were interested in the combination of enclosure and pcb or the whole kit.
Does the sensor in your project need to be taken outside to calibrate?
I stopped when I realised many sensors (like scd30/40) need this making it very impractical.. Has to be done once while powered on the whole time in a 7 day period.
https://sensirion.com/products/catalog/SCD41/
https://www.digikey.com/en/products/detail/sensirion-ag/SCD4...
Personally I've been very happy with Sensirion's sensors and I've played with the SCD41 quite a bit. The trouble with it for hobbyists is the assembly. It has what seems to me to be pretty picky requirements for soldering. I've attempted to do it myself but I keep managing to pop off the metal covering.
Haven't tried the Senseair Sunrise but such low power requirements are very very appealing because they mean the sensor can be battery-powered. The SCD41 isn't bad but powering it for a year means a lot more batteries. With a 1 min sampling period, the SCD41 uses 1.5mA while the Sunrise uses 21µA.
I think they're around 60 bucks (e.g. the T6793) so they aren't the cheapest around, but they're good quality.
They have a normal header you can solder a few wires into. Probably the best approach for the Sensirion sensor is to oversize the pads a bit and use paste to re-flow underneath.
The way I soldered the SCD41 is with a pre-made PCB footprint, some solder paste and a mini PCB heater. I think the problem was too high heat. I need to try it again with low-temperature solder paste.
But for my application the Senseair Sunrise looks a lot better.
As a diver I use oxygen sensors, and those should be calibrated once every third day, and linearity can go bad from everything between 6 months to a few years.
If I went with a DIY solution i would definitively go with 3 sensors so one can at least use voting to determine which sensors to trust, and to measure relative drift.
This can still situation where either a bad sensor is marked as good, or a good sensor marked as bad, so a human operator is still required to monitor the decisions made.
Live in the PNW with only electric heating/stove/oven. Cracking the window very slightly was enough to keep CO2 relatively low (600-800). Had to crack the window more when the temp is around 70 outside, less when the temp delta is higher (cold or warm).
Eventually ditched the device once I understood how to keep CO2 low. The cloud integration was creepy. I could tell when my wife or I went to bed based on CO2 spiking near the sensor.
(Specifically the Wave+ though; the hub apparently will want to connect over wifi instead, so I think it's better to just go for the Wave.)
Different places I’ve loved have had significantly different characteristics for what co2 concentration defaults to.
I’m guessing a not so small proportion of mental health issues and things like chronic fatigue are actually breathing issues and sensitivity to higher co2 concentrations.
For me a big factor is I broke my nose long ago and don’t breathe as well as I should.
pollution, on the other hand, is a real concern. that's stuff like radon, VOCs, methane, dioxins, and SOₓ emissions. as such, one thing we should be doing with vigor and relentless focus is phasing out coal plants (if we were actually putting our priorities in the right place) rather than worrying about the sideshow that is carbon emissions.
It took me a sec to figure out you were talking about something totally different.
Have you used the wrong numbers here or are you advocating some novel and unorthodox ideas about CO2? Did you mean 5,000-10,000?
Because as far as I can tell, those (5-10%) are the levels where people start to do things like lose consciousness from CO2 poisoning.
"poisoning" is a needlessly loaded word in this context. CO₂ is literally critical for life. just about any molecule/compound at those concentration levels (outside of those we co-evolved with, like nitrogen) will have noticeable effects as well.
I think it was this one: https://www.youtube.com/watch?v=kUfF2MTnqAw
Sadly I remember it all.
I was lucky enough to avoid intubation, but I suspect I wasn't too far away from it. CPAP with pure O2/a high-flow nasal canula at 90L/min pure O2 (I initially couldn't tolerate the CPAP mask for extended periods due to an anxiety disorder, though I felt myself becoming more fatigued over time on the HFNC) was keeping me at 88-90% (arterial blood gas measurement) initially, and that slowly started to climb a few days into treatment.
My wife does not notice any difference in herself. I dunno if she's less sensitive or maybe less aware.
I have a Hydrofarm Autopilot CO2 monitor and it pretty much stays at 600-800 all day, but I leave a window cracked open and live in a naturally windy area.
[0] <https://www.snopes.com/fact-check/apartment-radiator-pandemi...>
[1] <https://blogs.transparent.com/german/luften-germanys-airing-...>
[2] <https://www.bbc.com/news/magazine-21537988>
Especially “Stoßlüften” (opening a window for a short period) or “Querlüften” (opening windows in opposite rooms to create a draft).
First thing in the morning we lüft, after cooking, we lüft, before going to bed…
It’s especially important in newer or well renovated houses/apartments, to get rid of excess humidity in order to prevent mold. Really new apartments are so well insulated that they have literal holes in the wall (Zwangsbelüftung) in order have some airflow.
Edit: I was so enthusiastic to write a comment about lüften, that I didn’t read your link which actually covers what I said.
We lüft the house in times of peace, and we lüft in times of war. We lüft the house before we lüft the house, and then we lüft some more!
We lüft the house as we wake up, we lüft the house at night.
We lüft it in the afternoon, it makes us feel alright.
We lüft the house in times of peace, we lüft in times of war.
We lüft it once, we lüft it twice, and then we lüft some more!
This is how a professional does it, and he teaches you how to do the same.
If I remember correctly, there were some studies that calculated you'd need to convert half of your room into a dense jungle to offset your own co2.
Also, plants release co2 at night, so even if they had any effect, it would be a bad idea to have them in bedroom to scrub air.
Meanwhile, in Latvia there's a belief that "caurvējš" (drafts) are bad for you and that you'll catch a cold if you're in it for too long.
I've read some arguments for and against that online (mentions of cold stress, muscles posssibly tensing up to remain warm leading to a stiff neck, possibly nose being a bit more dry and susceptible to things in the air), but people over here typically just accept it as "fact". I can kind of understand caution when it's -10 C outside, but less so when you're in a stuffy room and it's 20 C outside.
Curiously, people in some other countries don't have such strongly held beliefs.
https://www.rbth.com/lifestyle/328478-why-russians-afraid-dr...
I've lived in six countries, and old people everywhere want to keep their joints warm.
I have the issue where we love a cold house but my hands don't, at least when I work, so the house is very cold, 14ºC/57º at night or even less, I get up wearing very little and make coffee in a chilly kitchen with pleasure, but then go to work in my shorts right beside a heater.
And of course billions of people live like this right now, domestic coal or kerosene burners being one of the most pressing air quality issues in the world!
Living in a center of a city next to a 10-line highway opening a window drops a properly calibrated sensor into 400s inside a few minutes.
That isn't going to do a thing about CO2.
It should, because of the V in HVAC.
one of the reasons some people swear on living in houses build around 1900 where I live, the larger ceiling height adds air volume (there are other reasons like large windows, wooden floors, etc.).
Seems like we're forgetting that the objective is not to reduce CO2, it's to reduce the pathogens in the air.
Since it's difficult to measure pathogens directly, we use CO2 concentrations as a proxy, since high CO2 means poor ventilation which means potentially high pathogens.
You can be right that turning on circulation makes the number go down. But that doesnt matter. Over time the concentration can go up and up and up, even with h"v"ac running.
Few residential HVAC systems actually ventilate. The focus on energy-efficiency has been a bit blind to the need to get rid of od co2 & take in oxygen. You can get fancy energy-recovery ventilation (ERV) devices that actually do air-exchange with thermal coupling, to cool or heat the incoming air. But this sort of system is alas exceptionally rare.
With an ERV, the best thing that I found to do is wire it to my furnace such that when the furnace kicks on, it will trigger the ERV to start. Otherwise you'll get furnace blower cycles separate from ERV cycles and it won't be as effective.
I've taken to just running the HVAC fan at all times, regardless of whether heating/cooling is happening. This tends to even out the temperature throughout the house, as well as CO2 concentration, it keeps the air filtering through the HVAC HEPA filter, and the ERV can run continuously, so rooms rarely get above 600 ppm CO2. Unsure about the energy use impact, but the air quality difference is palpable.
Can you elaborate? We are considering moving into an older house and renovating. Adding insulation being part of the idea. Our current home has full foam insulation with erv so I am curious what difference you experienced.
First the off-gassing. It emits a lot of harmful compounds as it cures and I understand the emissions to go on for a long time. So if you mind about air quality it wouldn't be my choice.
Second is the potential for damp to build up in the building fabric. The foam is airtight so make sure the ventilation is right on both sides of it.
A bonus third is the pain of removing it when you need to do building repairs. With board or batts you can lift them out; with spray foam you have to cut then scrape off.
The only way you're going to bring down CO2 levels in your dwelling is to bring in outside air. The best way would be installing a heat recovery vent that will save some energy. The simple way would be to open two windows and stick the fan in one for a short time (blowing in for turbulence to clear out the corners of the room).
Leaving your windows open with passive circulation for a longer time is going to cool down all the stuff inside, wasting much more heat.
I also have other air quality meters. (I collect measuring devices.) I wish there was a do-it-all air meter.
Also, have you ever put all of your devices near each other to compare the variance between them all?
You can get wifi bridges as well, see https://devel.aranet.com/products/
I've seen Aranet4's on eBay for under $150 pretty regularly, so I'd look there.
https://github.com/ryansouza/aranet4-exporter-go
Their data sheet also advises calibration if used at “high elevation.”
Seems like a few snake plants would easily handle that level.
https://balconygardenweb.com/most-effective-co2-absorbing-ho...
"In a study at Naresuan University, Phitsanulok, Thailand, the snake plant can absorb CO2 at 0.49 ppm/m3 in the closed system."
That would require an enormous number of snake plants to do anything. A tiny apartment is 50m^2 * 3m = 150 cubic meters, so it requires 300 snake plants just to bring down by 1ppm (though not sure over what timescale or other assumptions in the work cited)
Because you need to take time into account and it's more coherent with the result of other studies (an optimist case with good sunlight but 0.4ppm/m3/m is ok I guess for young plant).
'The approximate amount of carbon exhaled by a single human in 1 d is 300 g, whereas the carbon content of 1 L of gasoline is 640 g. In comparison, a single Spathiphyllum in a 15-cm pot grown at a PPF of 20 mmolm–2s–1 fixed 0.8 g C per day, so it would take 400 plants to offset a single human or 845 plants to offset a gasoline use of 1 Ld–1.'
[1] https://www.realhomes.com/news/do-house-plants-remove-carbon...
Planting more plants is at least a step in the right direction. Everything else is more or less simply turning it into someone else's problem.
You're right that the practical consideration is important. It needs to be addressed and engineered to be made practical.
On top of that maybe we eat too much, but that's a off topic.
https://en.wikipedia.org/wiki/Carbon_dioxide#Below_1%
The most convincing evidence is from the ISS: at 5000ppm CO2, the crew experienced "headaches, lethargy, mental slowness, emotional irritation, and sleep disruption." - so you can feel too high a CO2 level and open a window (if you know to consider that as a problem which causes these symptoms).
The studies suggesting 1000ppm may be harmful are called out in the wiki article and it seems the jury is still out as to if the effects are real/are the result of CO2 and not confounding issues.
I guess I should look at some studies, hm.
Most people I know don't air out their room/apartment long enough and/or often enough.
And I have been thinking about getting some form of huge fan to speed up the airing exchange process in winter.
Would it work to just open small openings on opposite sides of the apartment and put a small fan on one and run it continuously? With the right fan speed that should be equivalent to the big 30 minute airing ever few hours, but I'd expect it would be less disruptive when it comes to comfort because it should result in much less temperature variation.
E.g. if you have a apartment in the 5th floor where always have a bit of wind and can open windows so that the wind flows through just opening it for 5min might have as much effect as other people get with 40min.
Or e.g. if you have the right kind of wind putting windows into tilting mode can work well and in other cases (like my apartment) you will leak heat with very little air exchange.
I have been thinking about using some sort of fan but haven't tried it out. Part of the reason is that in summer I just can keep the window open all the time and currently we have winter temperatures around 4-7C during the day and my room temperature is most times around 16C in winter anyway, so ... it's not too much of a heating problem (compared to people heating their room to 20+C).
We live in a nice suburb near the water so outside air is clean. I now crack the windows open and co2 stays reasonable. I feel much better.
Before this, I was anal about insulation and making sure windows were closed when the heat was on. Now I know that's not the right calculus.
I could have figured out that I feel worse in the winter at home and feel good the moment I step outside. But having the numbers shown to me really drove a change in behavior
This include some system for automatic air exchange (which also keeps the heat in and isn't prone to fungi and isn't loud/distracting and doesn't draw a lot of energy; not easy to get right at all).
Guess what basically is non existing in close to all modern apartments I have seen...
Instead they tell you you have to "appropriately" air you apartment and skipping over the fact that this might mean 3 times a day 30min no matter what temperature is outside (on dais you stay home all day).
around 5 minutes with windows fully open and heating closed will do the trick. You want to maximize air exchange while minimizing heat loss.
This is common wisdom in Germany but the rest of the world seems to either prefer to heat the outside air instead of insulating their houses or must live in very sticky rooms. I just can't imagine not ventilating a room regularly.
no it won't not at all it's a common misconception especially in Germany
EDIT: jut to be clear it does work if you do the 5m airing often enough, but this is where the problem comes in it is fundamentally unpractical. I mean I can measure it tomorrow (through after long airing after sleep).
most ideas about insulation circulating in Germany are only half thought thru and sometimes do more environmental harm then good (depending on the building).
Of course it would depend on the size of the room and windows but I would be very surprised if you got vastly different measurements.
And yes, you obviously need to do it multiple times a day but that is a given. That is a problem with how fast CO2 builds up again though.
So 55m no airing then 5min airing.
That's not at all something viable with home office, too disruptive.
Now if I would be fine with having it constantly roughly between 1000ppm and 1400ppm then I could air it out much less often (because the higher the difference outside/inside is the less volume of fresh air you need to let in to make it drop the same absolute amount).
I can't really follow how you checked and were able to come up with these number from apparently one single measurement?
I still think the main issue is that you are not airing properly. The best way is is to create a draft situation by opening windows that are across from each other. If you can open the front door, even better. Again, you need to FULLY open windows, no in between state. Like fully open. If you don't have to remove the plants from the window still, you are doing it wrong. Having windows half-open will do barely anything for air circulation.
If you are not able to sharply drop the CO2 in a few minutes, there might be something else going one that you haven't mentioned. Maybe a HVAC system like another commenter suggested.
> Now if I would be fine with having it constantly roughly between 1000ppm and 1400ppm then I could air it out much less often (because the higher the difference outside/inside is the less volume of fresh air you need to let in to make it drop the same absolute amount).
I mostly use 1.2-1.5k ppm as a signal that it is time to air again. Obviously it is not realistic to never go above 1k ppm and that is fine. Long term exposure might make you slightly sleepy but a few hours of it are probably fine.
So I guess the 15 times would kind of check out if you wanted to keep the CO2 constantly low but that would be indeed excessive.
I had done measurements in the past and just doubled checked if I remembered correctly and how a 55m wait 5m airing cycle would work by doing it for the first 6 or so hours of my day.
> I mostly use 1.2-1.5k ppm as a signal that it is time to air again.
The think is if I as much as reasonable possible air out my apartment for 5min when it hit 1200ppm it e.g. just now went down to around 1000ppm...
And yes the airing situation in my apartment is not optimal, but that is with what I meant a lot of German "common knowledge" and (worse) regulations are often not fully thought through. It's based on the "how it should be" situation and blindly applied instead of how it actually is. And a lot of apartments in Germany have sub-par airing conditions in Germany, including worse then mine.
In Italy, the tradition has always been that when you wake up in the morning you open windows and let the air change, but the "new generations" are forgetting this, just when houses are built (or refitted) in a much more airtight way.
The only way out, mechanical ventilation systems, possibly with a heat exchanger[0]), are still rare, even in new constructions, I have seen a lot of issues in the houses built with (badly designed) energy saving goals (original A and B classes) built or renovated in the last 15 years or so.
[0] which bring their own issues, needed maintenance, periodical cleaning of filters, sometimes noise, etc.
I was shocked to see how fast CO2 will build up in just a few hours. Specifically online meetings when I do a lot of talking seem to drive it up.
That said, opening windows will drive the CO2 down to 500ppm in a few minutes. I think the OP does not know how to properly ventilate a room. You need to completely open the window or even multiple windows. They probably just had it half-open which will waste energy.
Also, if you look at the actual limits, no 1.2k ppm is not horrible. It will regularly reach 1.5k or more for me. Prolonged exposure of that can make you a bit sleepy but there is not reason to panic.
So, ventilate a few times a day properly. Don't just have the windows open all the day or the heating bill will kill you.
Can you explain that? I recently started to leave the window open 1-5 inches and it's done a good job, I am curious why half opening a window is problematic.
So you want maximum airflow for a short time. Best way is to fully open windows on different sides of the house and hope that creates the flow.
Very common method in Germany, they call it Stoßlüftung.
I have exactly the opposite problem from you. I don't even have AC, plus I'm comfortable at 82F/28C inside so I can keep the windows open all summer. In winter on the other hand, "keeping the window cracked open" like people have commented is definitely not an option. All modern buildings have mechanized ventilation systems for managing this but I live in an old apartment without ventilation, so a large airflow for short periods seems to be the best approach to get fresh air without losing the precious heat.
The Halo can also control an air purifier, which has been really handy. It's pretty cool to see the air quality improve while the purifier does its thing. This was especially important when we had horrible air quality due to forest fires.
Edit: The app actually let's me export all data as CSV.