I've built some DIY air quality monitors. Radon sensors are hard to find.

In general from easiest to hardest:

- Temperature, humidity, pressure: many cheap, small and accurate sensors available.

- Particulate matter: many options as well though if you want good accuracy and silent fans you need to pay more.

- CO2: most sensors are actually just measuring other stuff (TVOC) and guessing CO2 concentration from that. You can get good true CO2 sensors from eg. Sensirion for $30+.

- VOC, CO, NO, O3 and other gasses: hard to measure reliably. Most sensors are comparatively large (few small SMD MEMS types exist), are power hungry (basically a heater element) and give you a crude estimate as they react to bunch of different gasses and the output is a mix of their concentrations.

- Radon: basically impossible for hobbyist. If you know of any sensor module I can buy below $100 in unit quantities please share.

Edit: I know airgradient are not hobbyists and they probably could get some radon sensors but it is still harder than for large companies. Their product definitely has the DIY vibe (but high quality) and I really like that it is easy to recreate and source all parts for it yourself, except the custom injection mold case.

I agree, I'd like to go with air gradient but i need a radon sensor

I just want to point out that the other device being compared actually includes a radon sensor and the cost of that device would be cheaper than the airgradient plus the radon sensor.

You can get a cheap analogue radon sensor. As others have pointed out, even if you do detect radon the typical solution is add ventilation.

Which is exactly what you do if you had a high CO2 reading.

Do you have any links to this? I’m very curious.

Just lookup radon test kit and how to deal with radon.

https://kagi.com/search?q=radon+test+kit+&r=us&sh=fA8r72RApl...

Why not measure something like CO2 and use that as a proxy?

The logic being that whenever you bring in fresh air, you decrease radon concentration.

And a high CO2 level means you need to bring in fresh air anyway, and you incidentally also reduce radon concentration.

I could be way off here though, happy to learn more on the topic as I don’t have experience with (dealing with) radon.

Because Radon actually causes cancer and ventilation is expensive. I’ve read many articles about people going nuts trying to manage CO2, but I think it’s useful to know if I’m being exposed to something that would actually result in early death as I’m more likely to take immediate action on that.