Thanks for sharing, this is interesting to me.

Generating negative pressure in a room isn't great for fresh air. You'll be sucking air through any opening- wall outlets, floor registers, ceiling light fixtures, gaps in baseboard trim, etc.

Might be simpler to augment your fresh air intake with a fan.

I wonder what the market size for this is. If it were a real product that wasn't super ugly in the bedroom, we'd use it. My BR is ~1500 ppm with two sleepers in a 10x12 room, and opening the window isn't an option.

Or just open a window, you'll also sleep better

Given the effort involved (unusually-shaped 3D printed duct and housing for the whole gizmo), ISTM it would make a lot more sense to fit the duct to the trickle vent and operate it in positive pressure mode. This would have lots of advantages:

- With positive pressure, the intake air doesn't pick up contaminants from the wall cavities and other nooks and crannies within the building envelope.

- A fresh air supply fan can be fitted with a high-quality filter (HEPA or near-HEPA) to supply air with approximately zero PM2.5. (This is a very, very effecive way to get indoor air that is cleaner than the outdoor air without substantial power consumption.)

- You can open the door without moving the fan! You can leave it on with the door open! And it may improve the air quality in the rest of the living space more than the under-the-door scheme.

In a very cold climate, it might make more sense to put something like this in a different room so that the unconditioned supply air could be mixed with conditioned indoor air farther from where anyone is trying to sleep.

For what it's worth, there are a couple vendors of paired decentralized ERVs that alternate which one is supply and which one is exhaust and blow all the air through energy recovery cores that buffer both temperature and humidity. They're intended to be installed in holes in the walls, but it ought to be possible to fit them to windows or trickle vents with some creativity to operate them without any permanent modifications to the structure. In a climate with serious weather, energy recovery can substantially improve comfort and efficiency compared to using unconditioned supply air.

Software people will do anything but learn to use traditional CAD...

Just kidding. But would you mind sharing what you find so compelling about CadQuery?

As a mechanical person, these code to CAD tools make as much sense to me as suggesting you should write programs with a compass and straight edge.

Achim, founder of AirGradient here.

Nice to wake up and see a hacker news post benefiting from our open source air monitor designs, especially with the original design that we started with so many years ago! Makes me realize how much AirGradient developed since these early days.

Did you consider linking the fan with the CO2 data and making this a demand controlled system? Like you control the speed (or just switch on / off the fan) based on CO2 levels?

I think this could have a few advantages in terms of energy savings, noise level etc.

Cool project. Will need to do similar soon at new place to deal with tech in a cupboard for heat.

900 is still quite high though - upper end of normal for indoor

there are other possible marketing oportunities for this, and other gasses. "The remaining trace (<1% volume) compounds contribute to the odor of flatus. Historically, compounds such as indole, skatole, ammonia and short chain fatty acids were thought to cause the odor of flatus. More recent evidence proves that the major contribution to the odor of flatus comes from a combination of volatile sulfur compounds.[2][28] Hydrogen sulfide, methyl mercaptan (also known as methanethiol), dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide are present in flatus. The benzopyrrole volatiles indole and skatole have an odor of mothballs, and therefore probably do not contribute greatly to the characteristic odor of flatus."

https://en.wikipedia.org/wiki/Farts

I don't want to use Python if I can help it, OpenSCAD is another "CAD as code" language. How does it compare?

I had no idea CO2 could mess with mood like that, makes sense though. Definitely something I need to try out. Thanks for sharing, and nice project btw!

I installed a through-wall fan (AC Infinity) in a poorly ventilated room and it greatly helped with humidity/temperature issues. Curious to measure the CO2 change following this article.