Did he write that the Aranet4 monitor costs "less than an hour of your time"? I don't think the average person gets 300$ an hour.
this post was submitted on 06 Jul 2026
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Not an average person no, but the article seems to be aimed more at the people running businesses - and I think more in terms of the value of all of the people crammed into your conference room slowly losing it to CO2 concentrations.
*If you get 10-20 people together in a room, I really hope they are costing the company more than $300 an hour.
Large commercial HVAC package units often have an option called an "economizer". It's just one or more dampers that allow the unit to exchange inside air with outside air. A typical use case is when the unit gets a call from the thermostat for AC and outside air temp is lower than the room temp.
It's more for heating and cooling efficiency than air quality. Its also very rare for homes to have this kind of setup due the added cost and the fact that, at least in the US, package units are much rarer in residential installs. Fresh air circulation systems are a custom job which means $$$.
I was looking for small systems a while back, and the situation is surprisingly disappointing there. It should be technically possible to get portable and window heat/AC units (not split-mini, as one needs a duct for ventilation) that can maintain CO₂ and humidity levels. For putting a floor on humidity, one would need a water intake, and for doing energy-efficient ventilation, one would want a counterflow heat exchanger. As far as I can tell, small all-in-one systems like this just don't exist.
You can get ERV or HRV ventilators with flex duct attachments, which do the heat exchange bit. They don't cost that much, though given that it's basically two fans and a heat exchanger, I was still kinda surprised how expensive they are. I mean, an air conditioner is a lot more complicated. I suppose that there just isn't enough demand to produce the kind of sales volume required.
looks for an example
https://www.amazon.com/Aprilaire-V22BEC-Recovery-Ventilator-Easy-Install/dp/B0CXQ8RPTR
You could drive one of those off an indoors CO₂ sensor and that'd give energy-efficient ventilation with CO₂ control.
Yeah, this really shocked me too.
Basically, we knew that high carbon dioxide levels would have negative effects, but we used to think that much higher levels were required to have an impact, like 5,000 ppm or higher.
Then in recent years, some people started doing experimentation and found that mental capabilities were significantly worse at 1000 ppm.
Just sleeping with my bedroom door closed
in a not especially airtight house
I get well over that.
Also worth pointing out that pre-industrial outdoor carbon dioxide concentrations were about 280 ppm. We've brought it up to about 420 ppm now. Makes it harder to ventilate to get rid of the carbon dioxide indoors than was once the case, because there's also more of it outdoors now.
I wonder if with the research on CO2 effects, if we will start to get CO2 filters in common appliances such as indoor heating and cooling equipment.
Places like the International Space Station already have to deal with this because they can't just open a window.
IIRC, lime or something like that can be used as a carbon scrubber, but it's not something that you'd want to do constantly and everywhere. Looked this up some time back.
searches
Soda lime.
https://en.wikipedia.org/wiki/Soda_lime
Soda lime is a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO). It is used in granular form within recirculating breathing environments like general anesthesia and its breathing circuit, submarines, rebreathers, and hyperbaric chambers and underwater habitats. Its purpose is to eliminate carbon dioxide (CO2) from breathing gases, preventing carbon dioxide retention and, eventually, carbon dioxide poisoning.[1][2]
Probably, if you want to regulate CO₂ levels in HVAC systems, best to ventilate to the outside and then run the exchanged air through a counterflow heat exchanger to preserve indoor temperature as much as possible.
IIRC, lime or something like that can be used as a carbon scrubber, but it's not something that you'd want to do constantly and everywhere. Looked this up some time back.
Oh I’ve got some limes.
Soda lime.
Oh, well I can go get some of that.
Soda lime is a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO).
Oh, so it’s not lime soda. It’s soda lime. Alright then… I’ve got some salt and milk.
best to ventilate to the outside and then run the exchanged air through a counterflow heat exchanger to preserve indoor temperature as much as possible.
Wait, I’m not supposed to drink it?
Actually, ppm in 1000 - 2000 makes for better sleep. But for worse thinking of course.
People who sleep in their cars, engine running and parked in a garage, sleep like babies!
Makes me think of all those sleepy and dazed hours spent in a classroom.
Yeah, I had a year of school in a very elderly school building with limited ventilation. When it was raining and all the windows were shut, I remember it being really hard to stay awake and focused. Didn't learn until many years later to recognize that and that those are the symptoms of excessively high carbon dioxide levels (at the time, I thought maybe it was "low oxygen", that everyone's breathing had used up the oxygen, since I knew that fresh air would wake me up).
I've been in some office buildings with poor ventilation that do the same thing, though not as severely as that school.
Management bros discover ventilation. Amazing. Here’s your $160,000 consulting fee
That's not fair. This is legitimately something that probably nobody really considers. For almost everyone, HVAC starts and stops at climate control.
This is absolutely something HVAC professionals consider, buildings with a central HVAC system are constantly mixing in outside air for exactly this reason. Installing co2 monitoring in rooms is also done for this exact reason.
This blog post is not for HVAC pros.
No, but it shows that hiring one is a worthwhile investment.
What about "I'm opening a window / going outside for some fresh air"?
And you think when people say that they're talking about CO2 levels?
I think that when people say they need fresh air, they are likely to be thinking that. Many people in a closed room for a time makes the air "stuffy". People may not realize it is CO2 on an explicit intellectual level, but realize it on another level.
Oh, so that's why you were ridiculing the author for sharing the idea? Because people may have a subconscious intuition about CO2 in the air?
Oh my, let’s get dramatic here.
Yes, that’s right. I believe that the concept of fresh air helping people in a closed room is not novel. In fact, many people are aware of co2.
But back in real life where we’re not angsty dweebs who confront people about minor comments online, I was really just making fun of corporate management culture. Hope that helps your understanding.
Maybe not knowingly, but people certainly judge a room as "stuffy".
So, because we may have this intuition, that makes this blog post worth mocking then?
Do we really need a blog to tell people about stuffy air?! I'm more and more surprised by how dumb people are. Soon we'll have blog posts reminding us to inhale and exhale.
This article is deliberately phrased to spark precisely this kind of comment thread, and we've all walked straight into it.
If you're in the same meeting for more than an hour, you're already not getting anything done.