Worse yet in residential hvac systems, you have a closed system. When the furnace kicks on, it pulls inside air to heat it up. That air displacement creates a a negative air pressure inside the home. The exaust plumbing is typically nothing more than pvc pipes that are placed right at the exterior wall of the house. This just causes all that exhaust from the furnace to just get sucked back into the home. Diluted with outside air, yes, but a significant amount of it is getting sucked back in. Now it's winter, you are running your dryer, and frying some bacon on the stove with the exaust. Some one is in the bathroom with the exaust fan on too. All that co2 is getting pumped right back into your home and then some.

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.

Actually, ppm in 1000 - 2000 makes for better sleep. But for worse thinking of course.

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.

That's not fair. This is legitimately something that probably nobody really considers. For almost everyone, HVAC starts and stops at climate control.

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.

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.