3 ms·

Many cheaper CO2 sensors require frequent calibration. Often they just assume the weekly min reading is fresh air (420), or something like that, which is extrem

Many cheaper CO2 sensors require frequent calibration. Often they just assume the weekly min reading is fresh air (420), or something like that, which is extremely imprecise. I bought the Aranet4 because it claims not to need recalibration except in exceptional circumstances. They suggest keeping the factory calibration unless you can guarantee a proper controlled environment. I don't have the equipment to test their claims, but the readings have stayed plausible for months with no calibration. Edit: Note that if you're using your CO2 sensor as a proxy for the rate at which the air in an occupied room is replaced with fresh air the calibration imprecision doesn't matter. You're probably eyeballing the second derivative over the course of minutes-to-hours. I use my CO2 sensor for that, but I also care about the absolute. There's some evidence that normal rates of CO2 in modern buildings make your brain foggy. I'm trying to figure out if a program better when I use various interventions to increase fresh air.

ahaucnx 4y ago
Yes the ABC is often an issue and can lead to an underestimation of the CO2 values. This often happens in non ventilated and relatively air tight rooms. We collect air quality data from many schools and see this happening in some classrooms that even over the unoccupied time during the night the CO2 will not reach ambient levels the next morning.
- p1esk 4y ago
  What do you think about Air Quality Egg product [1]? How does it compare to Aranet4? How do these two compare to AirGradient ONE product? Which chemicals are most important to monitor in a typical 40yo house in Florida: CO2, CO, NO2, SO2, O3? [1] https://airqualityegg.com/shop https://airqualityegg.com/shop
  - ahaucnx 4y ago
    I do not own an Air Quality Egg or an Aranet so I cannot really comment on both. In general most of the low cost monitors use similar sensor modules, e.g. Plantower for PM, Sensirion for TVOCs etc. What is important to ensure that the CO2 sensor is an NDIR or photo accoustic and not using estimated CO2 via a TVOC sensor that is very inaccurate. I would start measuring PM, CO2 and TVOCs in the house to first understand more about how well the HVAC system works. Then optimize it for low CO2 and PM. This should then flush out most of the internal pollution sources as well.
    - p1esk 4y ago
      I understand you might be biased, but still, why would you recommend getting AirGradient ONE over the competing products?
lucb1e 4y ago
Easy way to test pressure changes: have a small room with a well-fitting door. Ventilate it well, then put the sensor in there. Open and close the door fast (mainly to/from the almost-fully-closed position) to get pressure changes. The pressure will only change briefly, but if it didn't keep up with the airplane, it definitely won't keep up with this. Depending on how frequent the readings are, at some point while opening/closing you'll get readings during a change and an outlier if it's sensitive to this. (You can also fashion something with e.g. cling wrap and stuff, but this seems simpler and you don't use throwaway plastic or anything.) I've used a barometer on a plane before. When they turn on the pressurization system, it's very clearly noticeable, but not a huge change. (A train in a tunnel is worse.) I'd expect this would be a similar effect.
- TylerE 4y ago
  Pressurization has gotten better over the years. Modern planes generally pressurize (or depressurize, more accurately. Sooner and slower. Like, imagine starting to transistion to the target pressure - usually equivalent to 6-8000ft, over time, starting as soon as the door is closed for pushback, instead of only adjusting during the climb.

ahaucnx 4y ago

Yes the ABC is often an issue and can lead to an underestimation of the CO2 values. This often happens in non ventilated and relatively air tight rooms. We collect air quality data from many schools and see this happening in some classrooms that even over the unoccupied time during the night the CO2 will not reach ambient levels the next morning.

p1esk 4y ago
What do you think about Air Quality Egg product [1]? How does it compare to Aranet4? How do these two compare to AirGradient ONE product? Which chemicals are most important to monitor in a typical 40yo house in Florida: CO2, CO, NO2, SO2, O3? [1] https://airqualityegg.com/shop https://airqualityegg.com/shop
- ahaucnx 4y ago
  I do not own an Air Quality Egg or an Aranet so I cannot really comment on both. In general most of the low cost monitors use similar sensor modules, e.g. Plantower for PM, Sensirion for TVOCs etc. What is important to ensure that the CO2 sensor is an NDIR or photo accoustic and not using estimated CO2 via a TVOC sensor that is very inaccurate. I would start measuring PM, CO2 and TVOCs in the house to first understand more about how well the HVAC system works. Then optimize it for low CO2 and PM. This should then flush out most of the internal pollution sources as well.
  - p1esk 4y ago
    I understand you might be biased, but still, why would you recommend getting AirGradient ONE over the competing products?

lucb1e 4y ago

Easy way to test pressure changes: have a small room with a well-fitting door. Ventilate it well, then put the sensor in there. Open and close the door fast (mainly to/from the almost-fully-closed position) to get pressure changes. The pressure will only change briefly, but if it didn't keep up with the airplane, it definitely won't keep up with this. Depending on how frequent the readings are, at some point while opening/closing you'll get readings during a change and an outlier if it's sensitive to this. (You can also fashion something with e.g. cling wrap and stuff, but this seems simpler and you don't use throwaway plastic or anything.) I've used a barometer on a plane before. When they turn on the pressurization system, it's very clearly noticeable, but not a huge change. (A train in a tunnel is worse.) I'd expect this would be a similar effect.

TylerE 4y ago
Pressurization has gotten better over the years. Modern planes generally pressurize (or depressurize, more accurately. Sooner and slower. Like, imagine starting to transistion to the target pressure - usually equivalent to 6-8000ft, over time, starting as soon as the door is closed for pushback, instead of only adjusting during the climb.