I recommend looking at Zigbee devices. They are local-first and don't require an internet connection (or any network at all.) If you don't have any existing home automation software or hardware, then the easiest way to get started is probably with a Home Assistant Yellow: https://www.home-assistant.io/blog/2021/09/13/home-assistant...
I've been very happy with my $20 Zigbee air quality sensors that I bought from AliExpress [1]. No DIY required, just plug them in and pair them with Home Assistant. These cheap sensors don't really have quality components or accurate readings, but they're accurate enough to get a good sense of my air quality and set thresholds to automate extractor fans and air purifiers.
If you really need a commercial-grade and highly accurate sensor, you could look at this iQi Zigbee sensor for $300 [2]. But I would recommend the $20 ones from AliExpress for home use.
Were you able to get accurate CO2 readings from the AliExpress Zigbee sensors? I got two of them and the CO2 values from each were wildly wrong. I'm curious if I'm missing a calibration step.
I'm not sure how accurate it is but the values seem reasonable. It hovers around 360ppm for fresh air. I can see it creep up if I'm in my office with the windows and door closed, and it spikes up if I breathe onto it.
I've been very happy with my $20 Zigbee air quality sensors that I bought from AliExpress [1]. No DIY required, just plug them in and pair them with Home Assistant. These cheap sensors don't really have quality components or accurate readings, but they're accurate enough to get a good sense of my air quality and set thresholds to automate extractor fans and air purifiers.
If you really need a commercial-grade and highly accurate sensor, you could look at this iQi Zigbee sensor for $300 [2]. But I would recommend the $20 ones from AliExpress for home use.
[1] https://www.aliexpress.com/item/1005003815133870.html
[2] https://www.trutechtools.com/iqi-air-quality-monitor-v1-with...