bizzz

I wrote this back in March 2025, but the question feels even more relevant in the current zeitgeist.

Thanks! Yep, the goal is stable 500-600 ppm; now thinking about making it into a positive pressure setup (https://news.ycombinator.com/item?id=44374107).

Thank you, I did not consider it, but looks like positive pressure is a best practice and I'll be looking into that (mounting fans directly onto the trickle vent).

Achim, AirGradient was the key that unlocked this whole project for me, so thank you for creating it. Also, I see that you're still so active in the forums helping users (including me) out, double kudos!

That's a great suggestion about making it a demand-controlled system! It's definitely on the long-term roadmap. Right now, though, my system is still a bit underpowered for that. I'm in an "all fans on" mode just to get the numbers down to a barely reasonable level. If I could easily get the CO2 to a steady 500-600 ppm, then absolutely, dialing it back automatically would be the next logical step.

So, my immediate focus would be on improving the raw efficiency. Following a great suggestion in this thread (https://news.ycombinator.com/item?id=44369469), I plan to design a new mount to put a fan directly on the trickle vent itself to actively pull fresh air in. It feels like a more direct approach, and I'm curious to see what that does to the numbers.

Thank you both! I'll start with a small research into available HEPA filter sizes, pressure drops they entail, and noise vs power ratio of available fans. Then I'll see if any combination fits my trickle vent setup and theoretically gives enough air as an output.

Thanks for the detailed thoughts! You've given me a lot to chew on for the next version of this project.

I did briefly look at ERVs, but for a single room in an apartment building with central heating, that level of energy recovery is probably overkill. I'd be simulating the result of keeping the window slightly open, I don't mind the cold it's even better for sleep (and the heat is not a problem here).

But your core points about the system's location are a real lightbulb moment for me. Having the fan up by the window instead of as a trip-hazard on the floor would be a huge improvement.

I can remove the housing for the trickle vent. It's screwed on, so I can put it back later without violating my rental agreement. Then, I could 3D print a custom adapter to fit that opening perfectly, designed to hold one of the Noctua fans and a small HEPA filter like you suggest.

That feels like a much more elegant solution. Thanks for the inspiration! You've got the gears turning again.

Heh, never really thought there's a market for it. Though now I can imagine it being sold at some TV shopping channel. A solution to a problem you never knew you had.

Anyway, I think there are plenty of people who do not want to open windows and still have fresh air. But the amount of people who can't modify their room or for whatever reasons don't want to open their bedroom door is bound to be much less.

Now I'm curious, why don't you open your bedroom door? Me, I'm a light sleeper and other apartment dwellers will wake me up if I open the door.

Yeah, if you can do it, I'm all for it!

Good point for standalone houses! I live in an apartment, so everything you listed is backed by some concrete blocks. So, realistically speaking, the air in any meaningful amounts can only come through the window/trickle vent of the door.

Ok, someone please glue all the tiles together! I can't wait to see all this magnificence!