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Comment by cardanome | Hacker News Reader

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.

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// 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.

How can an open window waste money by heat loss but not cycle the air?

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.

I usually notice dizziness from 800 ppm on...

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