NetAtmo for instance sells, of all things, personal weather stations! Indoors and outdoors, they connect to your wi-fi and can be monitored on your iPhone or iPad. Verra cool.
Not the least the indoors monitoring I find interesting. Since I work, play, and sleep at home, I want to make sure I don't accidentally, much less habitually, find myself in an environment with a bad CO2 concentration or other hurtful conditions.
I got it now. It's very cool. The hardware seems solid, and it comes with cable and even batteries! And plugs for US, Eu, and UK, good touch. (It is made in France, I am not sure if they have a US shipping station.)
I haven't put up the outdoors unit (the small one) yet, 'cuz I need a ladder first. (It's easy though, you just need a screw in a place with no direct sunlight.)
But it's kinda fascinating to follow the graphs of even the indoors unit. It even makes a graph for ambient noise! And it was nice to see that while you could clearly see the CO2 graph climb once I settled down in my bedroom, with windows cracked it never came above the first level of concern, 1000 PPM (parts per million). (They say the critical level is 2k. Over that you really should air out.)
Wikipedia says about CO2: "At very high concentrations (100 times atmospheric concentration, or greater), carbon dioxide can be toxic to animal life, so raising the concentration to 10,000 ppm (1%) or higher for several hours will eliminate pests such as whiteflies and spider mites in a greenhouse."
When you get the station, you go to their web site and get an app, and you plug in the station to your computer or iPhone and set it up with an account and log it onto your wifi. Not difficult.
The iPhone software is decent. I hope they'll make an iPad version, so they don't have to be so economical with space and information. (For example you have two different "pages" for the outdoors and the indoors station. And you have to tilt the iPhone between normal mode and showing graphs.)
The outdoors station apparently measures pollution and tells you what the main one is (low, and ozone in my case). And the app has a nice weather forecast too.
The indoors station has graphs for: Humidity, Pressure, CO2, and Sound Meter.
The outdoors station has graphs for: Temperature, Humidity.
Both have a bar (not graph) which I think is pollution. Pretty vaguely, they call it "air quality".
It's pretty interesting. For example how volatile conditions are. Last night like usual I had windows cracked half an inch (my windows have a secure lock in that position). I always keep all my internal doors open. And then I put a floor fan on the lowest setting (very low) in the doorway of the room opposite my bedroom, pointed at the bedroom door opening. It seems this changed the CO2 levels in the bedroom from over 800ppm to 600.
When I got up, I turned off the fan. And later I noticed the CO2 graph change instantly at that point. In only five minutes, it went from 600 up to 800!
Also I have found that even with just the half-inch openings at the windows, the current wind speed has a big influence. Low wind versus fresh wind made another 200 point difference in CO2 levels.
Below, the outdoors whether station. I borrowed a ladder from a neighbor and we put it up. It's designed to hang on a simple screw-head. We're looking due south, so you'll see that it is shaded from the sun most of the day. For early morning shade, I had fabricated a very professional metal sheet from a coke can, which I think will work nicely.