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   Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:14:19 JST Rich Felker

   Is there any viable approach to a home CO2 scrubber? Or is altering HVAC system to pull and filter outdoor air the only viable option that doesn't involve just opening windows and undoing all of the AC's work?

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:16:12 JST Rich Felker

     in reply to

     Apparently seal is strong enough here that CO2 is reaching 1500-2000 ppm, which has to be source of headaches and not-getting-shit-done. 😱

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:23:20 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser No, high CO2 is unrelated to oxygen level being low. That's a consequence of their relative prevalence in air. Rather it's that CO2 itself is harmful to breathe in concentrations above a very low baseline.

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     InsertUser (insertuser@en.osm.town)'s status on Tuesday, 11-Aug-2026 02:23:21 JST InsertUser

     in reply to

     @dalias
     Not in HVAC but IIRC there are some heat exchanger type things that try to change out air while reducing the heat lost/gained.

     At a theoretical level CO2 scrubber sounds like it would be of dubious utility as they don't replace oxygen and high CO2 is the body's signal that O2 is probably running low.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:25:57 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser A CO2 scrubber needs to remove something like at most 1 kg per person per day, and practically somewhat less since you still have natural circulation.

     You can make a cycle scrubbing it with NaOH, but releasing the CO2 outside (or collecting it in cylinders to actually use it) and getting back NaOH to continue the cycle requires a lot of energy as heat. There might be an electrochemistry approach with membranes that's efficient tho? I'm not sure.

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     Jonathan (jmcrookston@mastodon.social)'s status on Tuesday, 11-Aug-2026 02:26:28 JST Jonathan

     in reply to

     @dalias

     It's very difficult to get CO2 out of the air. I've never heard of a CO2 scrubber.

     You could fill the area with plants I suppose. I've never done the math on how many plants would be needed to put a dent in a high CO2 level though.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:26:28 JST Rich Felker

     in reply to

     • Jonathan

     @jmcrookston I believe @whitequark did the math a few years ago and it wasn't pretty.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:27:18 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser Humans produce around a kilo of CO2 per day through respiration.

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     InsertUser (insertuser@en.osm.town)'s status on Tuesday, 11-Aug-2026 02:27:19 JST InsertUser

     in reply to

     @dalias
     CO2 doesn't spontaneously arise from nothing unless you're doing weird chemistry in your home, it's generally the result of respiration or burning both of which involve removing O2.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:29:14 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser The reason it's unrelated to oxygen level being "low" is that increasing CO2 by 1000 ppm is a huge relative increase in concentration, but decreasing available oxygen by the corresponding stoichiometric amount is below the threshold of measurement noise.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 02:38:59 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser The amount of oxygen you have to consume in a perfectly sealed space before the reduced oxygen concentration has any adverse health effects puts you many orders of magnitude over the *lethal* CO2 level.

     Reduced oxygen is NOT the issue. Presence of excess CO2 is.

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     InsertUser (insertuser@en.osm.town)'s status on Tuesday, 11-Aug-2026 02:39:00 JST InsertUser

     in reply to

     @dalias
     It's not unrelated, it's largely from using O2 to "burn" sugars as part of respiration.

     The variable accuracy of measuring devices is neither here nor there.

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     Luka R. (rubinjoni@mastodon.social)'s status on Tuesday, 11-Aug-2026 03:01:58 JST Luka R.

     in reply to

     @dalias Do you live in a (yellow) submarine?'A strong alkali like potassium hydroxide can be used to scrub CO2. I'm sure there are available solutions for small, air tight volumes (submarines, hyperbaric chambers, spacecraft). A simple DIY would be a pump running air through an alkali solution - maybe a big aerator for aquatiums (something that forms fine bubbles).

     Here's Hackaday inspiration:
     https://hackaday.com/blog/?s=Scrubber

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 03:01:58 JST Rich Felker

     in reply to

     • Luka R.

     @rubinjoni It's fairly obvious how to do it once. It's making it into a cycle where the only inputs are affordable and sustainable (so, probably a reasonably low amount of electricity and no other non-long-lasting consumables) that's the hard part.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 03:19:04 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser I don't think you understand this at all.

     This is not a submarine. It's not a closed system. It's a house with a very good seal (energy efficient heating and cooling). There is absolutely no way you can reduce the oxygen concentration in any meaningful way by breathing, burning candles, not even using a gas stove for cooking. There is just too much oxygen to begin with and it will be replenished faster than you can ever use it.

     The health hazard is CO2 concentration (or even worse, CO, if you have shit burning dirty, but that's not the issue here).

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     InsertUser (insertuser@en.osm.town)'s status on Tuesday, 11-Aug-2026 03:19:05 JST InsertUser

     in reply to

     @dalias Whether the bad effects happen soon or later I think you're still setting yourself up for bad effects if this is a system meant to run indefinitely.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 03:26:49 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser Fortunately this isn't an issue for me, but changing out the air is not a solution if the outside air is heavily polluted (e.g. with wildfire smoke).

     The reason not to do scrubbing is that it's hard to do efficiently, not that it's not a solution.

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     InsertUser (insertuser@en.osm.town)'s status on Tuesday, 11-Aug-2026 03:26:51 JST InsertUser

     in reply to

     @dalias If just scrubbing the CO2 was a good solution all the major buildings would just do that rather than have systems that involve changing out the air.

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 03:35:17 JST Rich Felker

     in reply to

     • InsertUser

     @InsertUser You really don't know what you're talking about.

     if, hypothetically, scrubbing had near zero energy input, or even had useful output products (like if it were done via an artificial photosenthesis-like process with sunlight as the only input) then it would be a perfectly good solution.

     The reason it's not, if it's not, is cost/efficiency. Not failute to solve the problem.

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     InsertUser (insertuser@en.osm.town)'s status on Tuesday, 11-Aug-2026 03:35:18 JST InsertUser

     in reply to

     @dalias
     If the replacement air needs filtering then it needs filtering.

     Scrubbing is a fundamentally a dead end solution that's treating symptoms rather than causes.

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     Zephyr (zephyrleifrenner@mastodon.social)'s status on Tuesday, 11-Aug-2026 06:26:00 JST Zephyr

     in reply to

     • Jonathan

     @jmcrookston @dalias an oxygen concentrator is a pretty simple device. It could grab O2 from outdoors and send it indoors

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 06:26:00 JST Rich Felker

     in reply to

     • Zephyr
     • Jonathan

     @zephyrleifrenner @jmcrookston The problem is not lack of oxygen. It's excess CO2. These are not remotely related.

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     Zephyr (zephyrleifrenner@mastodon.social)'s status on Tuesday, 11-Aug-2026 10:25:59 JST Zephyr

     in reply to

     • Jonathan

     @dalias you might be looking for a heat recovery ventilator: https://en.wikipedia.org/wiki/Heat_recovery_ventilation @jmcrookston

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     Rich Felker (dalias@hachyderm.io)'s status on Tuesday, 11-Aug-2026 10:25:59 JST Rich Felker

     in reply to

     • Zephyr
     • Jonathan

     @zephyrleifrenner @jmcrookston Well that's not what I was looking for but it's probably the more viable solution to the problem.