Does anyone know of a reliable and cheap CO2 monitor (other data about air quality is not needed) for a music room that will be kept almost tight closed with potentially more than 1 person playing music? I need to know when levels will rise above normal so that we can stop and take a pause to exchange air. I've done some research and found complains about fake products coming from the usual suspects, some of which use alcohol sensors disguised as CO2 ones, which of course don't work.
I've taken DIY into consideration, then again discovered they sell fake parts too, like some MH-Z19 modules found on Ali* and elsewhere.
The most important thing is that you use an NDIR CO2 sensor. The best are in my opinion from SenseAir (e.g. the S8 that we use in our monitors). Then you can also get them from Sensirion, Winsen or Cubic. I believe for normal operations they perform all quite well.
Important is that you can adjust the automatic baseline calibration duration if you operate the sensor in a closed space that does not regularly get fresh air. Ideally put it into a longer period like 30 or 90 days or switch off and manually calibrate it regularly. I believe not many monitors offer that flexibility out of the box.
If you have some basic electronic skills, you can actually look at our open source build instructions and just build the basic monitor with the CO2 module [1].
You may be over-engineering things. Since there's no specific cutoff or precise value you need before calling a break, you could probably work out what rate things would increase at per typical person given the volume of the room and then just have a timer. Something like "Calm - 120 people-minutes, Energetic - 60 people-minutes, so three people really going for it means we take a break every 20".
Maybe this isn't enough for you, but I know it's easy for me to get trapped in a rabbit hole of how to solve things in a specific way and at times I need to pull back and say "what am I actually trying to solve". I had this with co2 monitors, getting fairly into which one to get then I realised I can deal with this by just regularly opening the window. I don't need a specific number.
edit -
Air exchange may happen pretty quickly, depending on the room and surroundings, so it could be as easy as "every X minutes we take a moment to open the door and window".
This is pretty much irrelevant though. I have a CO2 monitor for a closed space. Heavy exercise with the door closed will set off the 1500 PPM alarm every time. Do I care that it is off by maybe +/- 200 PPM? Not at all. It still absolutely serves its purpose of sounding an alarm when the air gets stale.
Thanks, I read about the need of recalibrating sensors, although didn't imagine that would be needed so often. Thankfully I recently moved to a very clean air area with trees and such, so exposing the sensor to clean air would just involve moving it a few meters outside.
Mine is indeed not perfectly calibrated since it sometimes gives value that are lower than the outside air, but the scheme of things, being off by 20 or 50ppm isn't going to change anything
Mine is indeed not perfectly calibrated since it sometimes gives value that are lower than the outside air, but the scheme of things, being off by 20 or 50ppm isn't going to change anything
I bought a co2meter.com model RAD-0301 ~6 years ago that was probably the cheapest prebuilt NDIR unit at the time. It just shows CO2 ppm and temperature.
It looks like they've slightly improved the features and dropped the cost more on their followup model https://www.co2meter.com/products/co2mini-indoor-air-quality... this is not going to be lab grade accurate but if it works as well as their old one it's great for the price and fits your requirement.
I'm a fan of Apollo Automation's AIR and MSR sensors that do a bunch of things, including CO2. They're ESP32 based, very easy to integrate with Home assistant with good UX.
Happy user of the Airthings Wave Plus (same as View but without a display). Major feature requirement was being able to fetch the sensor values with just a Bluetooth connection.
.. pretty much all instrumentation requires semi regular calibration, it varies by how often and how serious you are about exact results.
Many CO2 meters are sensitive to dirt | dust | crud build up ( see article ) and should be reset semi regularly as per the manual (or by the linked site guidelines if you've gotten a cheap one with no documentation).
Unfortunately my Jinping's temperature sensor does not agree with sensors of 3-4 different makes I have it always reads 3-4 degrees C below the others.
Yep same here. Temperature seems weird. It has offset option but didn't work correctly for me. CO2 and PM seem ok, but I don't have anything to calibrate with except outdoors.
