The idea is to use CO₂ levels to control your HVAC system. The HVAC system should be able to draw fresh air from outside or recirculate air from inside, depending on CO₂ level. This is a standard option on modern HVAC systems, and there are standard sensors for it. Better systems sense temperature, CO₂, CO, humidity, and smoke. This is a huge win for rooms where the people load varies widely, such as hotel function rooms and classrooms. Such control systems save money, because, when nobody is using the room, they detect that CO₂ is low and cut down the ventilation rate. When the room fills up, the CO₂ level goes up, the fans speed up and the outside air intakes open until the CO₂ level comes down. There are smart control units which manage heat, fans, vents, and air conditioning compressors. The hardware pays for itself in power consumption.
And yes, you can get this stuff Internet-enabled, although that's mostly for remote maintenance. The HVAC works just fine without connectivity.
Surprisingly, this technology is a tough sell. Except for convention hotels. They get this. They're in the competitive business of keeping large numbers of people comfortable and coming back. They have big rooms where the people load may go from zero to a thousand in minutes, and go back down an hour later. It's a huge win for them.
Well, in the Office for regulating CO2-vs-O2 it's competing with the timeless, very-low-maintenance and low-cost combo of keeping-plants-and-occasionally-opening-a-window.
Also, it takes about eight trees to absorb the CO2 emitted by one human. The contribution of houseplants is tiny. Especially since they usually don't get full sunlight.
That's an argument to be made to the hotel or office owner. The user has no control on the HVAC and is forced to open the window or turn on electric heaters to cancel it.
It's also $20 in singles from China. Coupled with whatever microcontroller you want, it's totally possible to have a distributed net of CO2 sensors for a low cost per node.
That being said, it's a ton of work and this is an excellent solution with much quicker results.
This cuts down on the work if all you want is to measure your CO2 level: you can get a $3 Wemos and a sensor, (solder pins, figure out the sensor connector), flash Tasmota, and you'll have it already reporting on MQTT over wifi. I would argue it's even easier than installing and maintaining Linux on a RPi.
We're looking to add a Co2 sensor to our IoT lineup and the MH-Z19 looks promising. It's also really small too :). You can also choose from 2 different ppm sensitivity from the factory and can get it on Aliexpress.
Here's the project I'm working on:
Here’s the kind of stuff it can do: https://www.acurite.com/access-my-acurite-remote-monitoring....
I’ve also had an Acurite display with some segments of digits that looked funky depnending on viewing angle. It was usable but kind of bugged me. I contacted them and they RMAd it quickly and easily for me (they just sent a new unit). For this reason, their easy availability on Amazon, the reliability and battery life I’ve had with half a dozen of their sensors deployed in and outdoors, I’ll keep buying them when I need this type of thing in the future. They don’t ever lock up or need fiddling with, so they’re kind of boring in that they just keep working until the batteries go flat. The widespread open source support is also certainly nice :)
I am using a Sonoff RF Bridge to talk to 433MHz sensors. It is also supported by Tasmota.
"They found that, on average, a typical participant’s cognitive scores dropped 21 percent with a 400 ppm increase in CO2."
If this result is reproducible, this is quite concerning considering:
"In surveys of elementary school classrooms in California and Texas, average CO2 concentrations were above 1,000 ppm, a substantial proportion exceeded 2,000 ppm, and in 21% of Texas classrooms peak CO2 concentration exceeded 3,000 ppm."
Just try to open the window at least once a day.
Disclosure: I'm not an expert, simply got interested in this lately as I strongly feel its impact on my productivity.
Seems like a simple solution, other than there's a good half-hour of sub-17 degree temperatures right at the start of the workday, which isn't exactly a great motivator to start working. Unless you are skilled at typing with winter gloves on, I guess.
And on the subject, do we have O2 level monitor as well?
Time to go shop some plants?
And during night, the plants would just produce CO2, which would presumably get accumulated, making the whole situation worse.
 - https://io9.gizmodo.com/5955071/how-many-plants-would-you-ne...
Not sure if/how this would work mobile, though.