I am living in an area with periodic very high air pollution. So opening the windows to bring CO2 down will bring in fine dust pollution.
I retrofitted my house with a demand controlled fresh air ventilation system that takes outside air runs it through a set of high performance filters and pushes it into the house.
I can consistently keep PM2.5 levels at zero and CO2 below 600ppm.
I wrote an article about it [1] including detailed charts about CO2 build up.
I have such system running 24/7 for 5 years now in my apartment. It costs $20/month in the winter because it needs to heat the freezing air coming in. There is also noticable noise if I am doing physical activity and it needs to blow the CO2 out more quickly.
$20/month is quite good for 7x24 heating of winter air. Could you share some details about the heating mechanism for incoming air, e.g. wattage, airflow, physical size? e.g. this combo fan+heater has a 1300W heating element, which would add up quickly in power consumption, https://www.deltabreez.com/RAD80.php
How often do you need to change the inbound air filters?
max wattage = 1400wt, av airflow = 40 m3/hr, size 20 x 20 x 7 inch, there are 3 filters, I just wash the coarse filter every 2 months, and replace the hepa filter once a year. I don't replace the coal filter as I don't have odors problem.
"There is also noticable noise if I am doing physical activity and it needs to blow the CO2 out more quickly"
significantly increases my sense of the strength of the evidence base that a device like this is actually doing its intended job. The idea of a repeatable (and repeated) experiment based on principles that we know a priori must be correct (that our lungs exhale more CO2 than they inhale, and at a greater scale during vigorous exercise)
Somehow it's more convincing than if poster had even said, 'I set a CO2 generator up and looked at the ventilation device's activity indicator and saw it increase whenever the CO2 generator's output setting was increased".
Rather, one hears the device working harder, when doing an activity that's familiar to all of us, in a repeatable way.
Also, the poster didn't have to tell us that lungs exhale more CO2 than they inhale, rather leaving that to our internal models of how that works. If they described that overtly, it would somehow already make me slightly more skeptical of the overall assertion of the device's efficacy.
I think the statement is made more powerfully convincing precisely because it leaves it to us to infer the implications of the obvious bits. When it's our own subconscious reminding us of the priors (1. lungs expel more CO2 during vigorous exercise than normal, and 2. many machines are noisier when they have to work harder to accomplish the task they are designed for), we intuitively trust that our own model of the situation is accurately informing us more than if someone else had to tell us that those underlying assumptions were correct.
I wonder how other demonstrations of innovations of less-apparent efficacy can be directed towards presenting their evidence in this more intuitively convincing framework. (Note I'm not saying I have particular reason to accept the poster's description without further diligence, merely that it 'feels' more convincing in a powerfully intuitive way, which is what I'm after here).
Like 'dependent variable X should be something familiar to everyone, drawing on principles that most people would have already ascertained a priori, and, 'dependent variable Y should manifest as an un-instrumented artifact of the device in question, one that can be intuitively perceived with as few opportunities for technical obfuscation (which could otherwise give rise to either intentional misinterpretation or simply misapprehension) as possible.'
(in the example, this is the device making more noise).
Anyway, I found it very satisfying to read that sentence from the poster.
Lower than in a typical office conference room during a meeting.
I still can't understand why the allied trades didn't press for building refits while everyone else was home and the "do something" sentiment among CEOs anxious to bring people "back to work"* was high.
* Please don't say "back to work"; it's propaganda that presumes remote or home can't work. Try "back to office" for something neutral, or consider "butts in seats" to throw shade on contentless managerialists who can't evaluate if someone's productive.
the trades were dealing with bigger problems, generally
construction was an essential industry, they didn't stop working during the pandemic. that being said, a lot of construction involves people in close quarters with each other, which was a major risk factor for COVID, and so there was a bit of work trying to figure out how best to get construction going and also not get all the workers sick. And there has been a worker shortfall in the trades for a while now, so it's not like refits could've significantly ramped up with nobody to work on them.
I did the calculation, at that rate that investment will never pay off. Besides, I find it hard to believe compact heat exchangers can exchange meaningful amount of heat at 40 m3/hr flow rate.
They can't, but you don't run them constantly at a low rate. They cycle on and off to hit your targeted air exchange rate. That would be about a 50% duty cycle on low, so like 15 minutes on, 15 minutes off, constantly.
They're definitely not "free", but they do return a lot of the heat you're using. 90% or so is pretty standard.
I have one-direction air flow in the apartment, where inbound clean air enters at one side of apartment, and exhaust exists the other side. The scheme that you mentioned would take clean air and throw it back outside, doesn't make sense for me.
When they say a lot of them, they mean, a LOT: "Realistically, you would need hundreds of plants in any one room in your home to compensate the CO2 emissions from just one person."
Because that would require a lot of plants.
A human exhales about 2.3kg CO2 per day. So that's 12/(12+216)2.3kg or 630g of carbon. A plant maybe absorbs 1g a day? Lets say a bit more... You probably need somewhere in the range of 500 indoor plants.
I don't think those numbers are applicable to house plants. Crops grown in a greenhouse are specifically grown to increase their mass in as short a time period as possible. Regular house plants usually don't increase their mass that much (you don't really want them to), they don't get nearly as much energy and nutrient input as greenhouse crops.
Algeae. Bubble your exhaust through some water, gain back some of your heat too. Maybe produce Hydrogen on the side. You could feed animals with the excess algaea.
Can you elaborate on "Standalone air purifiers work but they quickly lead to high CO2 concentrations inside rooms t"? How do air purifiers increase co2...?
My guess would be that in order for a standalone air purifier to work one has to limit the ventilation, which quickly leads to high CO2 concentrations in small urban flats.
Yes correct. The CO2 increases by humans and air purifiers do not remove CO2 or bring in fresh air. To have the air purifier work effectively you need to keep your windows and doors closed.
> To have the air purifier work effectively you need to keep your windows and doors closed.
Isn’t it the case that you can open windows to the extent that the air purifier CADR can cope with the influx? Then they are still “effective”. The relative air quality inside and outside is also highly relevant. I say this as someone with AGs, since I frequently do this dance when CO2 rises.
If your outside air is clean enough that you can afford to open a window with a purifier running, you probably don't need the purifier. I have two Xiaomi ones running 24/7, with CADR 300-350 on both. In colder months (which are 7-8 per year) they're running at maximum speed for most of the time (~2300-2400 RPM). Every window and door is shut, all gaps are plugged with expanding foam. Even with all that, the indoor PM2.5 almost never goes below 2-5 µg/m³, with jumps up to 30-40 µg/m³ when it's really bad outside.
Opening a window even for a few millimeters is enough for PM 2.5 to go to a significant portion of what's happening outside (which is almost always hundreds of micrograms, sometimes thousands), and no purifier can beat that. Maybe if I put ten of them in a row, but it's expensive and noise will be unbearable.
I have 2x 400m3 CADR purifiers and 4x AirGradients to monitor to Home Assistant. But I live in a fairly clean air city. It’s the pollen count that can be high. I suppose my point was I often trade going from 0 to 6 PM2.5 to reduce CO2 from 1200 to 600 for a while. Whether or not that is smart is one for the jury.
Sorry, probably not much help from me here. I've been using DIY stations thrown together from ESP32 development boards and low-cost Plantower sensors (PMS5003 and PMS7003). They're surprisingly accurate — my measurements over the past three years closely match the official government data (which is collected using calibrated "professional" air quality stations priced at $10k or more).
It's cheap, but you have to do everything yourself. A friend of mine did something similar, but using ESPHome and Home Assistant, and I think he didn't have to write any code at all, just a bit of YAML to tie it all together.
Most indoor air purifiers have low purifcation thoroughput compared to the space they are designed for (30 min to 5% PM2.5 concentration migh be a typical filtration rate). If you model that as an exponential decay it's about 10% per minute, so a leak of unfiltered air which would replace 1% of room air per minute would result in a steady state of ~9% unfiltered air, or twice the contamination the filter was rated for.
It really depends on the outside pollution levels. In our experience indoor purification reduction with air purifiers correlate with outdoor pollution levels. So if it's really bad outside opening the windows just a little bit will already let a lit of dirty air on with which the purifier might not be able to effectively cope with.
There was quite some work involved because the house was originally very leaky and for this system to work it needs a very good sealed home. So I spent quite some time and money to close the leaks. It probably cost me a few thousand USD to get it to this point but for us it was definitely worth it. Especially because we periodically have extremely high outdoor air pollution.
I use a FLIR One on Android. I've charted internal leaks (where cold air blows in through cracks) and external (where heat escapes through eg old windows).
Wait for a cold day (eg 0C), heat the house, investigate everything you can. My 1930s London house has SO many leaks, I've spent 3 years slowly fixing them.
I have a talk I should give on using 12 Govee hygrometers to back-calculate moisture (absolute humidity) coherent per room, as I was charting moisture loss to trace air leaks.
How did you use the thermal camera exactly? Any tutorials on that?
I have a garage, and I had issues with using the thermal camera - if the building materials were not uniform they reflected/radiated IR unevenly. It could show a piece of uninsulated area as hot and very well insulated as cold.
Get some wash-off spray-on chalk (essentially spraypaint that won't survive the next rain, because it's made to disappear when hit with rain/a hose). That should give you sufficiently uniform surface emmissivity to deal with those problem spots.
Industry standard in HVAC is to use a door blower to provide positive static pressure and then use a fogger. It works quite well since you have a direct visual indication and are not deriving loss from a secondary observation (temp/humidity).
I built a well insulated 9'x12' shed in my backyard to use as a workshop and for growing sprouts and seedlings. I installed a Cyclone Dual Air Single Room High-Efficiency Energy Recovery Ventilator from Home Depot. That unit was about $1000. It works quite well and my shed is super comfortable to work in year round.
I installed a larger ERV (about $2000) that is tied into our house central air. It has been a huge improvement to the comfort in the house.
I don’t like it. That’s how you end up with kids that are allergic to everything and have weak immune systems overall. I understand the CO2 control but let the dust and pollen flow!
Not sure if you are sarcastic or not but the place I live has at times air quality classified as "Hazardous" and then hospitals are full of people having problems to breathe.
If you are concerned about the zero pm 2.5 environment, studies show negative health impacts from pm2.5 even on very low concentrations and the WHO just last year lowered their guideline levels to only 5 ug/m3 pm2.5.
I recall that allergies to some degree are caused by too little or too much immune system stimuli early in life. Remember that allergies are a malfunctioning of the immune system, treating non-hazardous things as hazardous and causing unnecessary inflamations.
It's obviously better to breathe clean air than dirty air, but there is a point to be had that being in a "too clean" or "too dirty" environment when your immune system is still calibrating itself could have long-term negative consequences.
It's not one spectrum from "too clean" to "too dirty". It's at the very least two. For example, let's say pollen and coal. What you're talking about, having allergy issues from too little exposure, applies to pollen. Let's call those "adaptive particles" (term I just made up).
What you're talking about does not apply to coal. The ideal amount of coal particles in your lungs is zero. There is no age where it helps to get exposed, no allergy to avoid getting. Let's call these "non-adaptive particles".
If you live in a city, it's very likely that the negative impact from these non-adaptive is way worse than the negative impact of missing out on the adaptive particles. Breathing the air, you're increasing your risk of asthma a lot to decrease your chance of allergies a bit.
I don’t know where you live but the OP talks about London which has the same issue than here in Paris and is probably better than most large city in South East Asia. You can drop your pastoral dream of dust and pollen. The pollution is mostly diesel exhaust, industrial fumes and tire residues. That’s extremely unhealthy.
Not really in my experience. My air purifier and separate air quality sensor both show near zero levels of PM2.5 in my house after running the purifier for hours but I can still see a lot of dust floating around with a flashlight.
I like the idea of having a vaulted space, where you can control your environment and be safe. You can venture out any time you want, but if you don't or your health does not allow it, you have a safe harbor for you to recover. And your kids. Most importantly, your kids.
You are going to die of heart failure, or in a road accident. Way way way behind that you're going to die of cancer, and about twice as far behind that are a bunch of other non-preventable diseases.
Others just keep downvoting this comment, I'll offer a counterpoint instead.
I live in a city with air pollution levels that are considered extreme by Western standards (which I've checked and compared multiple times). Frequent SO₂ spikes up to 10 milligrams/m³ (and sometimes even more); NO₂ at 150-200 µg/m³ or higher; yearly PM2.5 averages of 200+ µg/m³, and so on.
Respiratory illness rates are 4× compared to national average. Life expectancy is lower by about 5-8 years.
If you look at this page, in most the world CVD beats cancers by about 2:1. Over here the ratio is much closer to 1:1.
Well, let's hope so, because currently I am at full speed towards developing COPD (despite never having smoked) and personally know way more cancer victims than victims of traffic accidents.
Either way, I'm not sure what the relevance of motor vehicle deaths is, just because I might die in a car accident doesn't mean I don't exercise and eat heathy to avoid having a heart attack.
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.
> 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.
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.
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?
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 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.
People tend to forget that plants only respirate O2 during photosynthesis, which produces sugars from the carbon in C02 and stores them. When those are metabolized, the plant consumes 02 and puts C02 back into the atmosphere. It's why plants can live in sealed terrariums.
To really offset what a human produces, you need a lot more plants than you would probably be comfortable living with.
I live in a 1950s Swedish apartment house. Our main ventilation is an adjustable vent/hole in the wall, so just completely passive.
I feel like there is constant lüften going on with that, and wonder if such building standards explain why we don't have the same habits as the German one.
Similar with the building rules in the Netherlands. Houses must have passive ventilaton in each (bed)room, and some system to create at least a certain amount of airflow based on the size of the house.
Simplest way is passive vents on the windows and a central blow-out fan that pulls air in. The more modern way uses a heatexchanger setup to take heat from the outflowing air and use it to warm air being pumped into the house.
I recently visited the German Bundestag. The distinctive glass dome on top of it contains a giant ventilation shaft for the plenary room, along with heat exchangers to recover the heat. The exhibition didn't state it, but I presume the incoming air is warmed up this way.
This arrangement is called gravity, or buoyancy-driven, ventilation; warm air rises and generates an updraft in a central ventilation conduit connected to an outlet vent in each unit. The replacement air is “sucked in” through an inlet, also in each apartment.
It’s used in multi-story buildings everywhere, but it’s not as effective in lowrises.
It can be boosted by having mechanical ventilation equipment on the roof – a rooftop ventilator – pulling air through the exhaust flue more effectively, and modern apartment buildings typically have this type of mechanical ventilation. (So even if your apartment only has a passive vent in the wall, that doesn’t necessarily mean the entire system is passive!)
Today, the inlets may also be centralized; this allows for replacement air to be taken from wherever it’s the cleanest, eg. from the side not adjacent to a street. The air can also be filtered to improve its quality and even pre-heated to make heating more efficient and prevent the feeling of a draft.
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.
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.
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 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.
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.
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.
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.
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.
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).
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.
What worries me is any amount of elevated CO2 has a measurable cognitive decline. Even going from 400ppm to 600ppm has a statistically significant change. The climate crisis is making us collectively dumber. Opening a window can actually make you smarter.
The study you linked used C02 as a proxy for low ventilation, it wasn't measuring the effect of C02 on cognitive performance.
The navy routinely operates submarines at 3500ppm or more, and they've been conducting studies since the 60s which have failed to show a cognitive decline from levels as high as 30,000ppm.
Thank you, I didn't know that the Navy had studied this in submarines. I found a Navy paper that's a summary of that research and it frames it as "the relationship between CO2 exposure and cognition is debated" with many citations for further information, some supporting a link and some not. See PDF page 22: https://apps.dtic.mil/sti/pdfs/AD1103610.pdf
(To the other comment, the 2021 paper I linked is not "pop science".)
You're welcome. I bought into the C02 makes you dumber research several years ago and bought a C02 monitor and everything before I took the time to look into the research.
The context of the paper you linked is "stressors in a disabled submarine". It's not a summary of the Navy's research. It does contain a few paragraphs out of nearly 100 pages that briefly summarizes a few relevant studies, both civilian and military.
Here's the relevant section:
>While some studies have found that elevated CO2 may impair cognitive functions including decision making (Satish et al., 2012), attention (Schaefer, 1951), mental efficiency (Karlin, 1945), and mathematical processing (Sayers, Smith, Holland, & Keatinge, 1987), these findings are not consistently replicated (Rodeheffer, Chabal, Clarke, & Fothergill, 2018; Ryder et al., 2017; X. Zhang, Wargocki, & Lian, 2016; X. Zhang, Wargocki, Lian, & Thyregod, 2016). In fact, many studies have been unable to establish a relationship between CO2 exposure and cognitive deficits (e.g., Bloch- Salisbury, 2000; Francis et al., 2002; Sheehy, Kamon, & Kiser, 1982; Vercruyssen, Kamon, & Hancock, 2007).
It lists 3 studies showing a cognitive impact impact. 2 out of the 3 show that there is a cognitive impact at extreme levels far beyond the levels that build up in a conference room, or levels that we'll be exposed to because of increased atmospheric C02.
--Sayers, Smith, Holland, & Keatinge, 1987
This study showed a cognitive impact at 65,000ppm, but nothing at 45,000ppm.
--Schaefer, 1951
Showed that submariners were slightly affected after prolonged exposure to 30,000ppm
Then it lists 7 studies showing no impact on cognition even at very high levels. Out of 10 studies listed, 1 civilian study shows cognitive impact at 1,000ppm. The preponderance of the evidence indicates that that study is a fluke. By the way, this study is the one that kicked off the whole normal indoor levels of C02 make you dumber thing in the first place.
This statement:
>the relationship between CO2 exposure and cognition is debated
is in the context of whether or not concentrations of up to 30,000ppm seen in a submarine disaster will impact cognition, not whether 1,000ppm in a conference room will.
Because it sounds reasonable, it reflects your experiences (stuffy -> headache -> lack of concentration), and you want a clear solution. But humans fucking suck at causal analysis. We all fall for it. Best we can do is get upset at the communicator (news/magazine/whatever) to put pressure for them to actually do their job. But also it is important that we are willing to update our beliefs instead of doubling down. All too common armchair experts arm themselves and fight real experts, who get very confused/frustrated.
FWIW, CO2 can cause cognitive decline. I mean hypoxia is a thing. But usually CO2 levels are a correlating factor (confounder) rather than the direct cause. So we can use it as a tool to help, but it isn't the problem. These types of things are the hard part about causality and why we are so easily fooled (because it makes sense and reflects what we (naively) observe).
Lol TED talks are a joke [0]. But depending on where one lives, better air quality may be inside or outside. The cleanest air I can breathe locally is in my grow room that is completely sealed except for a HEPA intake w/ same size exhaust that resupplies all new air per ~5 minutes, while I smoke my spliff, and it is very noticeable. I think I'm dumb for a lot of reasons but now I can add CO2 to the mix.
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.
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.
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 see a lot of people who talk about CO2, and I hear almost nobody talk about CO.
CO2 is much easier for our bodies to deal with than CO. CO2 won't kill you unless it's at exceptionally high concentrations. In cold regions, gas burning furnaces produce a good deal of CO.
There are alarms for CO, of course. But in the course of researching CO & UL standards around alerting, I found that most consumer CO alarms don't even alert until CO is above 30ppm. Additionally, for UL-certified CO alarms with an ambient "max reading" function, they don't even report anything below 10ppm.
I agree. But in most homes/office spaces, there is no source for CO, so people don't worry about it too much. It's of course a different matter if people have to heat their house with coal firing or something similar. Every winter I heard stories about CO deaths in developing countries again. That's really sad :'(
You don't need to fire coal to produce CO. Both natural gas and propane produce CO when combusted. In a home, a small crack in your furnace's heat exchanger is all it takes.
It's very common for natural gas to be used to heat homes and office spaces, at least in the US.
Additionally, water heaters and dryers might use natural gas. Gas stoves do, too.
You ever notice how CO alarm instructions have a blurb about not putting the alarm too close to your furnace, or too close to a gas stove?
Additionally, in many states there is a requirement to have CO detectors anyway, and it is generally built-in functionality to modern smoke alarms. So it's a double whammy of many homes not having any source of CO plus having built in detectors.
I think you've sort of missed the point I was making. Yes, CO detectors will alarm when CO levels are high enough to kill you.
They will intentionally NOT alarm if there is a low, persistent level of CO that probably has devastating health effects over the long term (think 20ppm in your house all the time).
Some years ago, my furnace had a cracked heat exchanger and, unknown to me, was pushing CO into my living space. I only noticed by luck. I walked by one of my CO alarms, hit the "max level" button and thought to myself that 25ppm is quite high. So I reset it and checked it again the next day. Sure enough, it shot back up.
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.
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 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
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.
>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.
> 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).
It depends a lot on the outdoor airflow situation. I live in a 6th floor apartment in a windy area, and cracking a window for 2 minutes gets me below 500 ppm every time.
At my parents’ house, I have to leave multiple windows fully open for hours to get the CO2 reading to budge at all. The air is just too stagnant. Things improve a lot when I put a fan in front of one of the windows to blow air out.
(Another problem is that their HVAC system is always recirculating the air, so the room I’m trying to ventilate is continually getting replacement air from a 1500 ppm wing of the house).
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.
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 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.
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.)
The story here is quite odd. I also ordered a CO2 meter and it changed my thoughts about my apartment. But in a former life I worked in fluid modeling.
> At baseline, the levels in my apartment were already dancing around 1,200 (ppm)...(marketing numbers)... I flung open a window... Two hours laterthe Aranet still hadn’t budged below 1,000 ppm
Something is very wrong here if your house/apartment is getting cold and a CO2 meter near a window is not dropping. Author should take it outside and check to see a number <500ppm (probably closer to 420). Device could be broken or poorly calibrated. It happens.
As for air flow in the apartment, this can often still be quite a mystery and weird to solve. My bedroom would constantly be above 800ppm, and above 600ppm with an open window. The solution? Opening a window on the other side of the apartment (need to pay very careful attention to paths that air can travel). A cracked window in my bedroom, a cracked window on the other side of the apartment, and boom, my bedroom is constantly near 400ppm (near ambient levels in my area).
But opening any other window in the apartment would not lead to this solution. Houses weren't designed with air flow in mind. Lots of hard corners can make it difficult to move air around (eddy currents are a pain). I do sleep better and there's probably some cognitive increase (I don't buy the 15-50%), but one of the larger benefits is the temperature is more stable (stable temperature is a good indication of good air flow btw). So I do encourage others to try this problem solving, but just want to note that the solutions are non-obvious. If you're having these issues, brute force the solution. You'll over think it (I did) but you're too clever by half[0]. You're working with a chaotic system and even the state of a door that doesn't seem in the flow path might affect the flow. If it isn't working, try dumb things and also use temperature as an indicator in addition to CO2. You can always use a fan too (draw air in on the opposite side of the house).
> Something is very wrong here if your house/apartment is getting cold and a CO2 meter near a window is not dropping. Author should take it outside and check to see a number <500ppm (probably closer to 420). Device could be broken or poorly calibrated. It happens.
She tried that: "I wondered, briefly, if my neighborhood just had terrible outdoor air quality—or if my device was broken. Within minutes of my bringing the meter outside, however, it displayed a chill 480."
Up to that point, I also assumed the meter was broken, but if it still shows reasonable values outside, I'm afraid it's the house that's broken.
Check the ventilation system to see if it's working properly. It may need to be cleaned or replaced. Maybe have some plants in your home. Maybe replace the gas stove with induction.
Or accept the higher CO2 levels. CO2 isn't personally dangerous like CO is. It's not ideal, but I think those warnings about loss of cognitive function are excessively alarmist.
I'd guess the author has a window that doesn't open completely or doesn't have windows on opposite sides of the building. In my experience, it's much harder to get good airflow if the path looks like a U or an L, instead of a straight line.
Aren't you supposed to calibrate these by taking them outside and assuming that is 400ppm? If that's the case, you can't really use them to measure outside CO2.
I'm just learning about these, so I may not be understanding correctly.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
After reading lots of these types of articles I reached the conclusion that opening (multiple) windows for a few minutes a couple times a day is a must, no matter how cold. It also helps with CO, particulates from furniture, radon, viruses etc. Outdoor air is of course not that clean, so my solution is to run a small air purifier. It's quiet enough that I run it non-stop and rarely notice it.
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.
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.
Last year, I made https://github.com/pmarks-net/exhale to automatically ventilate my house when CO2 levels are high, using a smart switch connected to the bathroom vent.
You can use heat recovery ventilation to swap indoor and outdoor air far more efficiently than using a simple exhaust fan.
The basic idea idea is you run a heat exchanger between the air you’re venting outside and the air you’re replace it with. Commercial versions run around 1,000$ but you can DIY something that’s reasonably efficient for far less.
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.
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.
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.
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.
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?
I build a combined real CO2/ppm monitor 3 years ago and I leaned quite a bit about indoor CO2 accumulates in practice and how to actually prevent it building up at all. This is from a single sensor I moved around over months so I might have drawn the wrong conclusions but CO2 seems to "pool" at lover heights and "fall" over surfaces such as tables from a "source" such as a human breathing. So don't put it on your desk surface but somewhere else in the room.
Also it seems to take a long time for a well ventilated space to build up to high CO2 levels - days for my apartment. I could entirely prevent any buildup at measuring heights of it by not quite closing a window furthest from my apartment door. My theory is that movent in the hallways of my apartment building slowly pushed air out that window thus replacing the air in my apartment fully over days.
By not quite closed I mean closed but the lever that presses the window into its the seals only slightly engaged. A Year after I started my Measurements there was some maintenance done on the windows to make them more airtight. Since then I do not need to keep the window half closed anymore because I can't get the CO2 meter to show anything but baseline except when sitting right in front of me on my desk.
A CO2 meter doesn't have to cost $250. A good NDIR laser sensor component costs about $50. An acoustic one from sensirion about $40. If you're good with electronics you can integrate those with a $5 wifi microcontroller and you're done.
For completed products my Awair lite cost me €100 including VAT (so about $80 pre sales tax) and it also includes an NDIR sensor. As well as fine particle and VOC.
One thing to avoid are Chinese sensors which only use "eCO2" - these estimate CO2 levels based on volatile organic compounds and are virtually useless.
Also it looks like the author has not understood well how a CO2 sensor functions. It needs to see direct fresh air at least once a week or it won't be accurate. If you don't see a reading of 400 (outside CO2 levels) you're doing it wrong and you're measurements are off.
My house rarely goes above 1000 so I think this is part of what got her so scared.
> The meter’s cruel readings began to haunt me. Each upward tick raised my anxiety; I started to dread what I’d learn each morning when I woke up.
Does anyone else see the problematic nature of "knowing" too much everyday data?
This article suggests the fear started due to COVID. This seems like an obsessive-compulsive health anxiety thing. Seems likely given the author writes mostly COVID & health opinion pieces(and a great writer at that).
Like many with Apple watches, being able to constantly monitor your vitals can bring both peace of mind and rumination.
I can't help but ask...is this a healthy thing to be doing? You can't control the environment.
Probably because the topic of indoor air quality is a very interesting one which a lot of people here are interested in. I've noticed that some posts seem to get upvoted based on their topic rather than their content.
It doesn't work in a flat (well unless you are under the roof), but in my house I have 2 electric opening in the roof (velux) that I open nearly (unless rain) daily for 5 minutes to change the air and it works really well, whole house drops to around 450. I compared with opening only a "regular" window, and it doesn't work very well, the air stagnate around the window and the CO2 only drops within a few meters of the window, but still cools the house. I guess it's basic physics as hot air is lighter, but it shows the importance of air flow. Also, changing the air quickly conserves more energy as the rest (furniture, floor...) doesn't have time to cool.
Warning: CO2 is not always correlated with other kind of pollution. I live in Sicily where air quality is good, the climate is warm so we always have open windows. My Aranet tells me that in my office CO2 is around 500. However I've the Etna volcano under my ass here in Catania, so I've alarming levels of radon (for which I've other sensors). As long as I don't take the basement with windows closed, all is fine, but if I close after a few days I see very bad values (but now I installed a big fan continuously pumping air from outside to inside).
Yeah, he mixes and correlates CO2 with PPM which is unrelated.
> When Jose-Luis Jimenez, an atmospheric chemist at the University of Colorado at Boulder, first picked one up three years ago, he was shocked that it could hold its own against the machines he used professionally. And in his personal life, “it allows you to find the terrible places and avoid them,” he told me, or to mask up when you can’t
Let him stuck the aranet in his mask and see how the reading goes.
I have a question - is CO2 filterable by active carbon filter?
Maybe the author just mangled the quote? It sounds like the context was preventing COVID transmission, it even mentions masks. One can reasonably say that the CO2 sensor doesn't distinguish air breathed out by others (dirty) from air breathed out by others and then cleaned by an air purifier (clean, but higher in CO2 than the outdoor baseline). So, if you are in an urban setting where the expected particulate levels are non-zero, you can tell whether the air around you was cleaned by a purifier using a particulate sensor. If it shows zero, it was probably cleaned to some extent.
It's not. You'd need a dedicated co2 scrubber, and it would be a pain to operate - if you had it running at home, it would gain ~1kg in mass daily (or it would need a dedicated connection to outside to throw co2 out of).
Particulate matter, VOC, and other kinds of substances are a breeze to filter out compared to co2.
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.
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.
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.
From my experience relative air humidity matters the most. I'm trying to keep it between 50-60%. When it gets too high I have difficulty breathing. When it goes too low my skin is flaking.
Of the gas appliances... I have never heard anyone having issues with their gas stove as any cooking is usually followed by ventilating the kitchen.
Although I've heard a lot of horror stories about CO (carbon monoxide) poisonings from faulty appliances like water heaters.
A CO monitor is something I would recommend to anyone having gas appliances at home. Again, based on third-hand experience.
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.
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 bought a cheap CO2 meter that actually measured TVOC (or something else) and infered the CO2 from it. Didn't like it. Many things would case false positives: farting, cleaning something with alcohol, steaming food, etc. And it had no option to disable the buzzer which would beep loudly for minutes. Cheap CO2 meter didn't fix anything and created a noise pollution problem.
Did the author stop and wonder why CO2 was important other than some product manual saying so? CO2, in the blood, has a protective role against reactive oxygen species. Oxygen is itself damaging! You don't need to be artificially enhanced by way of superior atmospheric conditions after 9pm when you should instead be getting ready to sleep.
On top of that, if someone really cared about making their body utilize O2 better they would be outside doing hill repeats to improve their VO2max. Worrying about carbon dioxide being a hindrance is silly, because having perfect air doesn't by itself make your lungs bring O2 into the bloodstream better.
If someone is buying an air quality monitor for life extension purposes they should find one that detects PM2.5 and PM10, and figure out how never to breathe that stuff, daggers for the alveoli.
Furthermore, filtering the air doesn't magically reduce CO2. That's stupid. If the author really wanted to reduce CO2, they would have bought 20 plants and placed them around their house.
IIRC, it takes 7 full-sized trees to match the CO2 output of 1 human. Plants could help somewhat, but unfortunately probably couldn't even offset a cat.
Maybe you're right that 20 plants wouldn't be enough help, but growing a plant is a real method of replacing CO2 with O2. Running a box fan with a filter taped on it isn't. That was my point.
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.
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'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.
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.
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.
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.
Step one needs to be to buy a second monitor and verify that they both have the same reading in the same space. It would not surprise me at all if the monitors were simply inaccurate.
You exhale about 1kg of CO2 per day, 27% of it is carbon. Have you ever noticed your plants gaining 300g of matter per day? You need enormous quantities of chloroplast life in your house to help you - and to constantly shovel excess out, impractical.
I have heard about some people keeping an aquarium (with growth lights) full of algae and they swear by it, but maintenance is high.
I've considered this myself, but I have a feeling that if I did the math on it, it'd turn out that I'd need an impractical number of plants to keep the air quality at an ideal level
If you mean the size of the house, that's wrong. It depends on the number of inhabitants in the home and how often the home is ventilated. Considering plants grow in (lean) mass considerably faster than (adult) humans, the number of plants should be a much smaller number than "hundreds."
Household refers to the number of occupants in the house, not its physical size.
A family of 4 can easily create over 1,000 pounds of CO2 per year. Common houseplants like Spathiphyllum can absorb about 0.8g of CO2 per day, so we can be super generous and call it 1 pound per year. So you'd need around 1,000 plants, reduced depending on ventilation and how much exhalation you do outside of home.
For a trip to your local garden center and 20-30$ at your local home depot/general store you too can achieve the hidden aeons old solution to co2 buildup.
The "number one rated" plant, Bird's Nest Fern, will consume CO2 at the rate of approximately 2ppm per hour per pot.
So, if you've accidentally spiked your CO2 levels up to 2000ppm, one of these bad boys should get you back down to a mere 1000ppm in a tidy 1000 hours or so.... assuming you've evacuated all humans and animals from the house and nullified all other sources of CO2 emission.
There are a lot of great reasons to have indoor plants; just be realistic about their ability to meaningfully impact indoor CO2 levels.
Okay so 4 ferns would do it in 250 +- 100 hours then. I'm not saying one home garden will solve global co2 buildup I'm saying its significantly cheaper and potentially more rewarding as a hobby than trying to play god with air quality and a 1k budget. You're also not accounting for gaseous exchange rates related as a function to current air quality. Yes a terrible PPM is 2000 but your body produces less co2 as a result of reduced function in such an environment, therefore increasing the effect of any filtration.
The bottom line is that you need thousands of plants to offset the CO2 exhaled by a single person. From what I can tell the ppm estimates on that page you linked are pretty generous -- they seem to be talking about the plants affecting the CO2 ppm in a very very small environment.
I'm saying its significantly cheaper and potentially more
rewarding as a hobby than trying to play god with air quality
and a 1k budget
I don't think I agree with this dichotomy. It's like saying reading books is more fun than playing the guitar. You can do both! They're not really in conflict!
And anyway, you can do a lot with indoor air quality for 1K.
Good point. Not sure what area they're talking about. I didn't get into the exact math because no matter how you slice it it's kind of absurd. Here are some more objective numbers I found. I don't know how reliable the sources are.
One common estimate for humans seems to be 1kg of CO2 exhaled per day.
A single bird's nest fern is estimated to absorb about 0.0002677kg of CO2 per day.
So about 3,700 bird's next ferns in your house for each human being should even things out. Regardless of exact numbers this seems consistent with everything I've ever read over the years, that indoor plants are nice but the amount needed to really reduce CO2 is impractical.
say you cover 1/3 with ventilation and 1/3 by not being home for 1/3 of the day. It still wont be a small greenhouse with [say] 1200 plants but say 3 floors of 25x16 definitely seems doable. How much artificial light to keep them going?
I visited a guy one time who decorated his 5 room flat with the biggest possible plants one could fit in each room (with a few spots to keep them alive). The 14x4.5 meter living room was a 2 seat sofa, a small table with drawers, a tv attached to the wall, very thick wooden floor with big cracks all over and 5 enormous plants in pots the size of bath tubs. No amount of money could have improved it.
For a plant to pull CO2 out of the air, it has to do something with that carbon. For a plant, this usually means "growing". Unless your indoor plants grow very quickly, they are not doing much to reduce CO2.
Edit: Found some dude who is bubbling air through plastic bottles filled with algal cultures to scrub his air. Since algae does grow pretty quickly in the right conditions, this might be pretty efficient, albeit kinda gross looking. He could dry and weigh the algae to get a pretty good estimate how much carbon he has collected, and from there calculate how much CO2 he's removing. https://www.instructables.com/Simple-Algae-Home-CO2-Scrubber...
"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.'
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.
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.
