5 ms·

I've worked on environmental sensing iot projects and have seen the cost of co2 sensors. Almost all the cheap ones are VOC sensors which infer a co2 level by as

I've worked on environmental sensing iot projects and have seen the cost of co2 sensors. Almost all the cheap ones are VOC sensors which infer a co2 level by assuming the VOC output is from humans (rather than paint for example). Given the cost of the device I would be amazed if it wasn't a VOC based sensor. The cheapest CO2 sensors I've seen are well over $250, even in bulk. CO2 is quite innert, so it requires very precise and accurate components

dschuler 8y ago
I got an NDIR CO2 sensor on AliExpress for $20. Do you think one of those would just have low accuracy or be uncalibrated?
- bizzleDawg 8y ago
  I suspect both! I should compare a $250 one with the $20 one
  - pstuart 8y ago
    That would be a worthy HN post.
    - illegalsmile 8y ago
      Is that something HN is interested in? I do work and research with remote environmental monitoring stations and am always comparing sensors. Currently doing a precipitation gauge intercomparison study.
      - pstuart 8y ago
        I can only speak for myself and what I've seen discussed here over the years -- yes, it would be interesting. Why is better stuff is more expensive, how to make the cheap stuff work closer to the better stuff, and interesting findings from actually using them. Lessons learned are always interesting...
      - plmpsu 8y ago
        Very interesting.
      - aurbano 8y ago
        Please do! I just bought a couple of cheap co2 sensors on Amazon (2k positive reviews) only to find out that they may not be accurate. It would be amazing if you or anyone really could make a comparison between different models - and show whether the cheap ones on amazon and the likes are worth it.
- benjaminjackman 8y ago
  Would be interested to find out because if its just uncalibrated plotting out the relative differences it still would be useful (e.g. seeing a X% increase on whatever scale the sensor using at night versus day could provide enough of an indicator that something is going on and more investigations are warranted.)
- 05 8y ago
  Just test/calibrate them outside (400-ish ppm). Even if absolute measurements are bogus, they should do just fine to figure out whether it’s time to open the window..
- Matrixik 8y ago
  Also if someone is searching for PM2.5 particle monitoring: https://smartairfilters.com/en/blog/how-accurate-are-common-particle-counters-comparison-test/ https://smartairfilters.com/en/blog/how-accurate-are-common-...
bizzleDawg 8y ago
Looking at their materials[1], it's IR based and needs calibration. I'm sure it's output is interesting, but likely not super accurate given their started assumptions for the calibration process. Better sensors may be required before drawing any conclusions! [1]: https://www.netatmo.com/en-gb/helpcenter/air-care/4/installation-et-prerequis/4 https://www.netatmo.com/en-gb/helpcenter/air-care/4/installa...
clairity 8y ago
i’ve noticed this casually as well. i bought an airthings wave plus [0] a few months ago and the co2 and total voc readings seem pretty (but not perfectly) correlated. i live in a drafty pre-war building and my co2 peaks at around 1500-1600 ppm at night with doors and windows closed. it troughs at around 500 during the day when i have the doors and windows open (~400 is ambient from what i understand). tvocs typically peak around 600 ppb and trough at around 20 (under 100 is considered safe iirc), with the same cycle as co2. [0] https://airthings.com/us/wave-plus/ https://airthings.com/us/wave-plus/
- Robotbeat 8y ago
  413ppm is now ambient. Goes up higher every year (with a small amount of seasonal variation). By 2100, we may be at 800ppm if we continue and/or accelerate fossil burning (4 degrees C trajectory). https://www.co2.earth/2100-projections https://www.co2.earth/2100-projections Already a middling stuffy room, and would increase indoor levels 400ppm over today.
  - drpgq 8y ago
    I wonder at what point will people have active systems to lower their CO2 below ambient in their homes.
    - thatcat 8y ago
      You mean plants?
      - clairity 8y ago
        ha, i actually bought a bunch of plants from the nasa list a year-ish ago to help reduce co2 & voc levels: https://www.healthyandnaturalworld.com/best-air-filtering-house-plants/ https://www.healthyandnaturalworld.com/best-air-filtering-ho...
        hnick 8y ago
tossandturn 8y ago
I have developed custom Ethylene sensors in the past for customers, and Dynament (UK) is a manufacturer that I can definitely recommend if anyone wants to do this and go down the DIY electronics route without having to dig through a bunch of Chinese products to find the "right one". https://www.dynament.com/products/gas-sensors/standard-non-ex-sensors/ https://www.dynament.com/products/gas-sensors/standard-non-e...
- gnat 8y ago
  Cool! I worked at an ethylene-sensing IoT startup (fruit ripeness natch). What was the core sensor you used? (We were using off-the-shelf, but somewhat pricey, electrochemical sensors)
  - tossandturn 8y ago
    "MSH-P/HC/NC/5/V/P/0 - 3% Volume Ethylene = 0.4V - 2.4V" We built that into a custom SS body with a Delrin mounting insert, and ran the serial connections to a custom board that interfaced with up to 8x sensor locations (in conjunction with some other sensor elements). The elements were ~US$200/ea ~4.5 years ago. These are fancy interpolated IR absorption sensors internally, so any gases of similar concentrations could throw off the readings; depends on the environment. Would be BEST to calibrate to local atmosphere conditions of the installation, but that's not really something you can sell. :P
- willsr 8y ago
  I remember looking into this years ago, and the prices were in the $100-$200 range for low volumes. Was this your experience?
  - tossandturn 8y ago
    Yes
ancarda 8y ago
Are there any brands or products you would reccomend for measuring CO2 in my house? Ideally with some way to hook it up to my computer.
- bizzleDawg 8y ago
  It looks like things have moved on quickly since the other year when I was more involved in this! This company does some good products, some of which are fairly easy to interface: https://www.gassensing.co.uk/products/ https://www.gassensing.co.uk/products/
forthispurpose 8y ago
Can you recommend the lowest cost CO2 sensor that one can buy that would give reliable readings?
- andor 8y ago
  The "TFA Dostmann AirCO2ntrol" devices are popular in Germany. Searching for "co2 meter" on Amazon.com one of the top results is an identical looking device. It measures with an infrared spectroscopy-based sensor, which should be quite accurate. There are a few good software packages for recording data, e.g. https://github.com/vfilimonov/co2meter https://github.com/vfilimonov/co2meter.
- gsich 8y ago
  MH-Z14
- Ductapemaster 8y ago
  Repost from my comment above, but for a couple hundred bucks you can get an accurate CO2 sensor that reads out via USB-serial to a computer. I use them at work and we've shown they are quite good over the long term. Plus to recalibrate, you can just take them outside. https://www.co2meter.com/products/k-30-co2-sensor-module https://www.co2meter.com/products/k-30-co2-sensor-module
gsich 8y ago
MH-Z14 or Z19 are cheaper, around 25€. With optical measurement. I have a few of them, they seem accurate enough. I calibrate them every 6 months by placing them outdoors.
vagab0nd 8y ago
Thanks. I was about to get a cheap one on Amazon :D Sort of related, I'm living in a newly constructed house and I'm interested to know the indoor air quality. Any recommendation for a comprehensive in door air quality test solution (either device(s) or hire someone maybe)?

dschuler 8y ago

I got an NDIR CO2 sensor on AliExpress for $20. Do you think one of those would just have low accuracy or be uncalibrated?

bizzleDawg 8y ago
I suspect both! I should compare a $250 one with the $20 one
- pstuart 8y ago
  That would be a worthy HN post.
  - illegalsmile 8y ago
    Is that something HN is interested in? I do work and research with remote environmental monitoring stations and am always comparing sensors. Currently doing a precipitation gauge intercomparison study.
    - pstuart 8y ago
      I can only speak for myself and what I've seen discussed here over the years -- yes, it would be interesting. Why is better stuff is more expensive, how to make the cheap stuff work closer to the better stuff, and interesting findings from actually using them. Lessons learned are always interesting...
    - plmpsu 8y ago
      Very interesting.
    - aurbano 8y ago
      Please do! I just bought a couple of cheap co2 sensors on Amazon (2k positive reviews) only to find out that they may not be accurate. It would be amazing if you or anyone really could make a comparison between different models - and show whether the cheap ones on amazon and the likes are worth it.
benjaminjackman 8y ago
Would be interested to find out because if its just uncalibrated plotting out the relative differences it still would be useful (e.g. seeing a X% increase on whatever scale the sensor using at night versus day could provide enough of an indicator that something is going on and more investigations are warranted.)
05 8y ago
Just test/calibrate them outside (400-ish ppm). Even if absolute measurements are bogus, they should do just fine to figure out whether it’s time to open the window..
Matrixik 8y ago
Also if someone is searching for PM2.5 particle monitoring: https://smartairfilters.com/en/blog/how-accurate-are-common-particle-counters-comparison-test/ https://smartairfilters.com/en/blog/how-accurate-are-common-...

bizzleDawg 8y ago

Looking at their materials[1], it's IR based and needs calibration. I'm sure it's output is interesting, but likely not super accurate given their started assumptions for the calibration process. Better sensors may be required before drawing any conclusions! [1]: https://www.netatmo.com/en-gb/helpcenter/air-care/4/installation-et-prerequis/4 https://www.netatmo.com/en-gb/helpcenter/air-care/4/installa...

clairity 8y ago

i’ve noticed this casually as well. i bought an airthings wave plus [0] a few months ago and the co2 and total voc readings seem pretty (but not perfectly) correlated. i live in a drafty pre-war building and my co2 peaks at around 1500-1600 ppm at night with doors and windows closed. it troughs at around 500 during the day when i have the doors and windows open (~400 is ambient from what i understand). tvocs typically peak around 600 ppb and trough at around 20 (under 100 is considered safe iirc), with the same cycle as co2. [0] https://airthings.com/us/wave-plus/ https://airthings.com/us/wave-plus/

Robotbeat 8y ago
413ppm is now ambient. Goes up higher every year (with a small amount of seasonal variation). By 2100, we may be at 800ppm if we continue and/or accelerate fossil burning (4 degrees C trajectory). https://www.co2.earth/2100-projections https://www.co2.earth/2100-projections Already a middling stuffy room, and would increase indoor levels 400ppm over today.
- drpgq 8y ago
  I wonder at what point will people have active systems to lower their CO2 below ambient in their homes.
  - thatcat 8y ago
    You mean plants?
    - clairity 8y ago
      ha, i actually bought a bunch of plants from the nasa list a year-ish ago to help reduce co2 & voc levels: https://www.healthyandnaturalworld.com/best-air-filtering-house-plants/ https://www.healthyandnaturalworld.com/best-air-filtering-ho...
      - hnick 8y ago

tossandturn 8y ago

I have developed custom Ethylene sensors in the past for customers, and Dynament (UK) is a manufacturer that I can definitely recommend if anyone wants to do this and go down the DIY electronics route without having to dig through a bunch of Chinese products to find the "right one". https://www.dynament.com/products/gas-sensors/standard-non-ex-sensors/ https://www.dynament.com/products/gas-sensors/standard-non-e...

gnat 8y ago
Cool! I worked at an ethylene-sensing IoT startup (fruit ripeness natch). What was the core sensor you used? (We were using off-the-shelf, but somewhat pricey, electrochemical sensors)
- tossandturn 8y ago
  "MSH-P/HC/NC/5/V/P/0 - 3% Volume Ethylene = 0.4V - 2.4V" We built that into a custom SS body with a Delrin mounting insert, and ran the serial connections to a custom board that interfaced with up to 8x sensor locations (in conjunction with some other sensor elements). The elements were ~US$200/ea ~4.5 years ago. These are fancy interpolated IR absorption sensors internally, so any gases of similar concentrations could throw off the readings; depends on the environment. Would be BEST to calibrate to local atmosphere conditions of the installation, but that's not really something you can sell. :P
willsr 8y ago
I remember looking into this years ago, and the prices were in the $100-$200 range for low volumes. Was this your experience?
- tossandturn 8y ago
  Yes

ancarda 8y ago

Are there any brands or products you would reccomend for measuring CO2 in my house? Ideally with some way to hook it up to my computer.

bizzleDawg 8y ago
It looks like things have moved on quickly since the other year when I was more involved in this! This company does some good products, some of which are fairly easy to interface: https://www.gassensing.co.uk/products/ https://www.gassensing.co.uk/products/

forthispurpose 8y ago

Can you recommend the lowest cost CO2 sensor that one can buy that would give reliable readings?

andor 8y ago
The "TFA Dostmann AirCO2ntrol" devices are popular in Germany. Searching for "co2 meter" on Amazon.com one of the top results is an identical looking device. It measures with an infrared spectroscopy-based sensor, which should be quite accurate. There are a few good software packages for recording data, e.g. https://github.com/vfilimonov/co2meter https://github.com/vfilimonov/co2meter.
gsich 8y ago
MH-Z14
Ductapemaster 8y ago
Repost from my comment above, but for a couple hundred bucks you can get an accurate CO2 sensor that reads out via USB-serial to a computer. I use them at work and we've shown they are quite good over the long term. Plus to recalibrate, you can just take them outside. https://www.co2meter.com/products/k-30-co2-sensor-module https://www.co2meter.com/products/k-30-co2-sensor-module

gsich 8y ago

MH-Z14 or Z19 are cheaper, around 25€. With optical measurement. I have a few of them, they seem accurate enough. I calibrate them every 6 months by placing them outdoors.

vagab0nd 8y ago

Thanks. I was about to get a cheap one on Amazon :D Sort of related, I'm living in a newly constructed house and I'm interested to know the indoor air quality. Any recommendation for a comprehensive in door air quality test solution (either device(s) or hire someone maybe)?