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Ask HN: Best way to remove CO2 in a bedroom?
I know that CO2 sequestration/capture is imperfect and expensive; however, I was wondering if there is a doable way to remove CO2 in a bedroom at night, to improve air quality why we sleep?
- dsq 2y agoOpening the window should help, unless the outside air is highly polluted. One can also install a fan that either vents air out of the room to the outside or draws fresh inwatds.
- mousetree 2y agoPlant
- cpach 2y agoNot sure that’s effective enough to make a practical difference.
- hobs 2y agoIt's pretty hard. Recently I saw https://www.youtube.com/watch?v=xWRkzvcb9FQ https://www.youtube.com/watch?v=xWRkzvcb9FQ which has gigantic barrels of algae and direct light input and air being blown through them and still the scope of what you need to make a serious dent in your CO2 output is pretty impressive.
- pawelduda 2y agoFan in the doorway
- sixthDot 2y agoand blowing to the outside
- Grazester 2y agoI have one that blows air in from the next room which has an open window.
- pawelduda 2y agoDepends I think (that is, if you care about cooling down the room too) If it's closer to the floor, it will be moving colder air, so you may want to point it inwards Closer to the ceiling and you'll be moving warmer air, so you want it to go out
- deleted 2y ago[deleted]
- hliyan 2y agoVentilation is usually the best way. Even when there is a temperature differential between the outside and inside, it's more economical to heat up / cool down in the new air than trying to scrub CO2 [1] If you have an air quality concern, you can start by installing an indoor air quality monitor with a CO2 sensor. [1] https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber
- alfiedotwtf 2y agoFrom this post, https://news.ycombinator.com/item?id=40688403 https://news.ycombinator.com/item?id=40688403 use the excess CO2 for your new hobby in welding
- everdrive 2y agoNot being snarky, but a window is one of the best options. Air conditioners can often be your worst option, as the air is recirculated more aggressively. We use a window fan that has multiple settings: circulate, ingress, egress. I find that no matter what setting you use, air is recirculated significantly well. On hot days, the fan is set on egress. This seems to do a really great job of removing excess CO2 while not bringing that much hot air into the house. We have a window fan running in the kitchen for the bulk of the year. We also find that simply cracking the windows in the winter makes a large and measurable difference in CO2, but not with heat.
- gandalfgreybeer 2y ago> a window is one of the best options. Add a fan and it's hard to find something more optimal and cheap for this problem.
- ratg13 2y agoAlso, don’t put the fan directly in the window, but a leave a small gap between the fan and the window to take advantage of Bernoulli’s principle
- everdrive 2y agoDo you have a good visual of what would be best here? I've been making sure my fan is as tightly sealed around the window as possible, but it'd be interesting to learn if there's a better solution.
- ratg13 2y agoThis teacher helps visualize this concept pretty well https://www.reddit.com/r/Damnthatsinteresting/comments/ul8mth/physics_teacher_shows_the_bernoullis_principle/ https://www.reddit.com/r/Damnthatsinteresting/comments/ul8mt...
- user32489318 2y agoYes! This video covers window and fans in more detail : https://m.youtube.com/watch?v=1L2ef1CP-yw https://m.youtube.com/watch?v=1L2ef1CP-yw
- weissi 2y agoWe leave our bedroom door open whilst we sleep which pretty much solves the issue. Leaving the ensuite bathroom door open also helps but not quite as much as the door to the hallway.
- anfractuosity 2y agoWhen using a CO2 sensor in my room, opening a window was very noticeable as a drop in CO2 on the graph.
- difosfor 2y agoPeriodically open your windows wide. If the CO2 quickly builds up though, you could perhaps just leave some windows cracked open. Or you should get some proper ventilation installed. If CO2 is high then other pollutants are likely also high.
- garrisonj 2y agoI want to experience pre-industrial co2 levels
- _nalply 2y agoYou won't experience a difference
- tgv 2y agoBreathing during sleep adds only little CO2 to the environment. Here's a calculator: https://www.omnicalculator.com/ecology/co2-breathing-emission https://www.omnicalculator.com/ecology/co2-breathing-emissio....
- underdeserver 2y agoI like the way you phrased that - "Breathing during sleep adds only little CO2 to the environment". It kinda sounds like you're trying to discourage them from trying not to breathe during sleep.
- spiffytech 2y agoMy CO2 sensor shows up to 2,600 ppm overnight if we don't actively vent our bedroom. 500-750 if we do, depending on which in-window fan model and how high we set it.
- tgv 2y agoThat's that's quite a lot more than expected. Isn't there another source of CO2?
- GeoAtreides 2y agoI have two true CO2 sensors in my room (SCD30, SCD41), and I can confirm the CO2 concentration rises to 2400-2900 ppm during the night. But it's very easy to vent, a draft will reset the concentration to background levels in a minute or so.
- guidedlight 2y agoIt’s typical for bedrooms to have a ACH (Air Changes per Hour) rate of between 0.35 and 1 So the CO2 is removed regularly.
- epgui 2y agoThis. I studied for like 12 years in the biomedical field and I don’t really understand why OP is worried about this.
- hollerith 2y agoHe could have an unusually tight bedroom. Also, ACH on windless nights will be manyfold lower than on nights with even a 2-MPH breeze.
- giantg2 2y agoDoesn't this assume forced air with the fan running for some percentage of the time? It's possible their fan doesn't run enough. It seems many people have that issue at least during some seasons.
- jonahbenton 2y agoThere is no small scale human comparable in room CO2 removal bio/tech. Human breath will increase CO2 in a closed room on the order of many hundreds of ppm over hours, while even "superplants" like those in an Algen Air will decrease it at best on the order of low tens. We need improvements of two orders of magnitude to have room scale impact. So the only answer is "fresh" air ventilation.
- giantg2 2y ago"There is no small scale human comparable in room CO2 removal bio/tech." Of course the tech exists, it's just not common. Some submersible tech and space tech used rebreathers or scrubbers to remove CO2 and increase O2 levels. Of course the reason it's not common is that outside of those use cases you can generally just open a window.
- stogot 2y agoDidn’t Apollo have scrubbers too?
- gandalfgreybeer 2y agoWhile not directly related to CO2 removal, for air quality, especially if you live in an urban area, adding an air purifier is very useful.
- secondcoming 2y agoIn the UK, 'trickle vents' are mandated in new build houses. They're little vents placed above external facing windows and doors that can be opened and somewhat closed. The goal is to allow moisture to escape to prevent mould but they also obviously allow constant airflow. They don't really allow bugs to get in either. video: https://www.youtube.com/watch?v=6_2SdLEbHcM https://www.youtube.com/watch?v=6_2SdLEbHcM
- fartfeatures 2y agoIn the UK, trickle vents above windows and doors were historically used for passive ventilation to prevent mould by allowing airflow. However, modern building practices and regulations, including stringent air tightness requirements mandated by Building Control, have shifted focus towards more efficient ventilation solutions like Mechanical Ventilation with Heat Recovery (MVHR) systems. While trickle vents are still used in some cases, their prevalence has decreased compared to earlier practices
- secondcoming 2y agoPossibly, my flat was built 3 years ago and has trickle vents all over.
- fartfeatures 2y agoCheaper option than MVHR but notably worse. Missed opportunity.
- timrichard 2y agoWe're in the process of getting windows replaced, and the window company said they are now mandatory on all new and replacement windows. Apparently, it became law in June 2022.
- secondcoming 2y agoSeems they're mandatory unless you're deliberately fitting leaky windows! > When windows are replaced, a background ventilator or ‘trickle vent’ should be placed in the new window. This will replace any ventilation you lost, when installing a new window, because your previous window was leaky. If replacing your window did not reduce the amount of useful ventilation, this should be proven, and more ventilation is not needed. [0] https://www.gov.uk/government/publications/home-user-guide-template/existing-home-ventilation-guide https://www.gov.uk/government/publications/home-user-guide-t...
- dakiol 2y agoI may be missing something (perhaps OP doesn't have windows?) but I open my windows in all the rooms a couple of times per day (in the morning and usually in the afternoon-evening). Isn't that enough?
- simonebrunozzi 2y agoYep, I assumed that either you don't have windows, or you can't open them during the night.
- vertnerd 2y agoDo you have a CO2 monitor? I bought one during Covid to monitor the classroom I teach in. I was surprised by how bad it got: well over 1000 ppm. When I brought the monitor home, I was surprised all over again by 1000+ ppm levels with just a couple of people and a cat. All the efforts to seal the house for energy efficiency were in direct opposition to advice to lower CO2 levels. The only reasonably effective solution that isn't absurdly expensive is to open the windows a little. All the time. You pay more on heating and cooling, but.. there is no alternative. The good news is that it gives you a reason to leave the drafty window air conditioners installed all winter long. And house plants have negligible impact on the levels. Keep plants for the aesthetic, but they aren't going to solve the problem.
- contrarian1234 2y agoAnother point in the "leaky" house's favor is that it doesn't get as dusty nearly as fast as one with an open window. Granted the severity of this issue depend on where you live :)
- faitswulff 2y agoIf you have an airtight home, you need a separate ventilator for the reasons you state. New construction building code often requires these.
- AifVI 2y agoTurning on a bathroom vent fan is remarkably effective. Based on the CO2 monitor in my basement utility room, turning on a bathroom vent fan in the upstairs lowers the CO2 in the entire house within a few hours. An energy recovery ventilator would be ideal, though, as it wares much less energy while still lowering your CO2 levels. It would be awesome if there were a way to actually capture and sequester in-home CO2, so that your in-home number could be lower than the outdoors. But I’ve never heard of such a thing.
- ghthor 2y agoHouse plants
- christina97 2y agoThey are practically useless in reality. You’d have to live in a greenhouse for them to absorb your CO2 basically.
- shrimp_emoji 2y agoWhat about like a tiny cactus on my nightstand? Will that help calm my anxiety and help me accept the inevitability of death and see it as the indivisible half of the miracle of life?
- KineticLensman 2y agoIt might take your mind off existential anxiety-related thoughts if you stab yourself on its spines in the dark.
- latchkey 2y agoYou haven't seen my house.
- colanderman 2y agoEnergy recovery ventilator. It will exchange indoor air with outdoor air while maintaining indoor heat and humidity. Unfortunately small window mounted models are hard to come by. Most are whole-home systems.
- joshdev 2y agoThis is the way. As others mention opening window is your cheapest option, but you lose a lot of your heating and cooling efficiency. We installed a whole house ERV for about $10K and saw a significant drop in CO2 readings.
- dzhiurgis 2y agoWhole home ones are only real ones having a chance to work. I’ve installed mine in about 6hours (but I do have moderately accessible attic). They are somewhat cheap too - at $1k or so.
- colanderman 2y agoI used to have a window mounted unit from a small company. It worked wonderfully in my bedroom.
- l1tany11 2y agoPanasonic ones go down to 50cfm, which is fine for a bedroom. That being said, everything in construction comes down to “it depends” because there is so much variability including just in execution. In California for instance there are mechanical whole home ventilation requirements, but those requirements are quite low and are commonly ineffective for the OPs goal depending on how the system is arranged. Same thing goes for the ERV. Often times the best way to solve the OPs problem is just to run the central fan (assuming there is central air) as that will exchange bedroom air with the rest of the house, which assuming the house is significantly larger than the bedroom, will basically solve the problem. If you are going to do an ERV I would recommend adding a filter box for allergens/dust/etc assuming the ERV you select doesn’t have one built in. Not expensive, it’s just a sheet metal box you put filters in, HVAC guys buy and make them all the time. If you want to spend even less money, and don’t have central air, you can install a bathroom fan in the ceiling/wall of the bedroom, and have it vent to the rest of the house but this takes a bit of thought with regards to airflow and how the air will mix. But even if all you are doing is effectively doubling the volume of your bedroom, that makes a big difference.
- victor106 2y agoWhat’s the best device to measure CO2 in a bedroom?
- casenmgreen 2y agoBuy a CO2 monitor. Then keep a window open enough to keep the air fresh. I find a few centimeters of gap is all that's needed.
- yuumei 2y agoMechanical ventilation with heat recovery is a common term (MVHR). Basically a fan but it tries to recover the heat lost in winter. Usually comes as a whole house system but there are some that do single rooms.
- shikon7 2y agoYou could try to use plants and a growing lamp for them to do photosynthesis.
- kkfx 2y agoVMC in general, for energy usage reasons (meaning opening the windows cause too {cold,hot} air inside, open windows (with eventual mosquito net if needed) when external climate allow that.
- epgui 2y agoThis is a bit of a nonsense question. The CO2 diffuses away rather quickly and there is no reason to worry about this.
- deleted 2y ago[deleted]
- christina97 2y agoYou clearly don’t have a CO2 monitor.
- christina97 2y agoI have spent a considerable about of time on this question: and it really seems there is no practical way to remove it. You can let it out by ventilating, but that’s about it. This realization has made me quite anxious about the Keeling curve.
- hollerith 2y agoIt is possible to remove it. If it weren't, then submarines full of people would not be able to stay submerged for months at a time like US Navy submarines routinely do. Right now it is pretty expensive like you point out, but if millions of people were to start wanting CO2-removal equipment, surely our civilization would find a way to get the price way down.
- hrtdc 2y agoIs there evidence that CO2 levels in the air matter to human health? Humans can tolerate a fairly wide range of blood CO2 levels. We have a buffer system in our blood, and we can use our kidneys to pick up the slack when ventilation (via the lungs) is suboptimal.
- bitshiftfaced 2y agoHave a fresh air intake installed on your HVAC system.
- spiffytech 2y agoI've found an in-window fan unit (blowing outward) is very effective at keeping CO2 levels down. Noisy, though. Before that, overnight CO2 levels exceeded 2,600ppm. Now around 700 or so. Can go lower if I crank the fan up. Now I have the new problem of poor thermal regulation. My window is directly above my HVAC duct, so cool air goes straight from my air conditioner through the fan and out the window. I plan to wire up a microcontroller to turn the window fan on and off based on both CO2 levels and A/C activity, but I'm not really happy with the the setup. Too hacky, too much noise, and I need to seal the window screen better to keep bugs out. I've tried just keeping a window open, with no fan, but my CO2 sensor indicated it wasn't super effective. Plus you have to make sure you close the window when it rains otherwise muggy air fills the bedroom.
- OutOfHere 2y agoFor the kind of technology available to us, it could cost up to $100 a day to buy enough "soda lime" to filter out the CO2. You'd want the "color changing" type of product. You would also need HEPA filters to ensure the powder was not getting in the air. Temperature sensors would also be needed to ensure it wasn't releasing so much heat that it causes a fire. The algae route is cheaper, but needs a lot of algae.
- Llamamoe 2y ago> For the kind of technology available to us, it could cost up to $100 a day to buy enough lime soda to filter out the CO2. Doing some napkin math based on quickly googled(maybe incorrect) numbers, 100g of lime soda can absorb 10-20L of CO2 depending on the setup. Random offer off a Google search is $30 for 1kg, and I can get it cheaper locally. To go from 1200 ppm to atmospheric 421, you need to remove ~0.8L/m³. For my 50m³ room, that's 200-400g of lime soda. CO2 takes several hours with closed windows to build up that high, though, and it'd need a control loop to avoid wasting the lime soda by scrubbing below atmospheric CO2 levels... I thought you were being hyperbolic but, damn, yeah, this doesn't sound very viable ):
- OutOfHere 2y agoThanks for the math. The parent comment has been slightly edited. I'd ideally want the CO2 to be the preindustrial level of under 300 ppm. The reason is that I suspect it could lead to maximum alertness and a feeling of well-being. Note that some ventilation still is needed during the day to get O2 and remove VOCs, so the calculations are affected. In your calculation, remember to account for the presence of people who constantly breathe out CO2. This and the need for some ventilation add to the cost.
- Llamamoe 2y agoThe amount of O2 removed from the air is negligible compared to the impact of elevated CO2 on human gas exchange tbh. I doubt you'd have much benefit going down to 300 instead of 400, and it introduces a whole other problem - aiming at sub-ambient CO2 targets makes ventilation increase the amount of scrubbing you need to do instead of decreasing it. I imagine the increase in cost would be massive. But yeah it'd probably be better to base the calculations on co2 breathed out by people. But like I said, that's just some quick, likely incorrect math to land in the right ballpark.
- giantg2 2y agoDepends on your climate/weather, local noise/crime, and construction of your house. Opening a window can be an option. So can an open bedroom door. The best option to me is to just leave your air handler fan set to "on" rather than "auto". Of course you need forced air for this. My house is relatively newer and moderately sized. It still seems to keep the whole house CO2 levels like 50-100ppm over outdoor levels. The bonus here if you're looking for "air quality" and nor just CO2 is that your air handler filter should catch many particulates (although most aren't capable of high merv ratings, it still seems to help).
- ydnaclementine 2y agoSleep with the door open, if opening a window isn't an option. At least you won't be hotboxing yourself with CO2 in a tiny area
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