1. 28

  2. 3

    Can anyone recommend a cheaper CO2 sensor? Suitable for the same purpose: monitoring air quality in room.

    1. 1

      there are some sensors on aliexpress for ~20 bucks. buyer beware and all that though.

    2. 3

      As for what to do to improve CO2 levels at Recurse Center, one option would be to hire an HVAC person to install CO2-driven ventilation. Depending on how the building is currently ventilated, you may be able to install a simple damper that opens to let the HVAC system pull in fresh air when CO2 levels get too high, and and that closes when they are reasonable, trying to strike a balance between energy efficency and healthy air.

      Something like this: https://hvacsolutionsdirect.com/catalog/Duct-Smoke-CO-Detectors/CO-Duct-Detector-Kit/Young-Regulator-DEMAND-AIR-CO2-FRESH-AIR-Damper-SKU2669

      There’s fancier variants as well if energy efficiency is a concern.. but the basic idea anyway is to have something that regulates fresh air intake based on CO2

      Or.. you know, if someone happened to have a Raspberry Pi with a CO2 sensor laying around, just buying a motorized damper and controlling it with the Pi :)

      1. 1

        Don’t do that. You want an ERV or an HRV. A simple air exchanger will cause humidity issues. As a bonus you’ll get filtered air with an ERV or an HRV

        1. 1

          Nah. HRV does nothing for humidity, it’s the same as regular ventilation as far as that goes. ERV will help retain whatever the indoor humidity is. So if you’re in a cold climate with no A/C or dehumidification, it’ll raise indoor humidity since it’ll “hold in” humidity that otherwise would have moved to balance with outside air.

          Not necessarily a bad thing if you’re in a dry climate, but not something that helps with moisture problems.

          If you’re in a hot/humid climate and you have dehumidification, then an ERV will help offload the dehumidifier/AC.. but then the A/C was already doing the work to keep mold at bay.

          Basically once you start mixing in energy recovery, humidity becomes complex. It’s good stuff, but if you just want to keep CO2 levels down then just a regular old fresh-air intake for the HVAC is much cheaper and simpler.

      2. 3

        Awesome! I love these kind of little gadgets and the insights they can sometimes give us about our daily lives. I was surprised at how much the sensors cost. A packaged CO sensor (with readout and enclosure) cost me $22 on Amazon. A bare CO2 sensor on Digikey cost $57 and a fully packaged one costs ~ $100 on Amazon.

        I suppose this might be a result of the demand volume and sector: I can see this being used in industrial settings, rather than in every home.

        Put this on a list of DIY projects to do …

        1. 2

          In few months I’m actually going to start working on my air monitoring project. Found a bunch of air sensors that I’m planning to combine into a portable device for when I’m traveling around.

        2. 2

          although I think to really make a dent one would need to buy a lot of plants or perhaps acquire some vats of algae.

          a LOT of plants. Infeasible.

          I had an ERV installed at home to reduce the amount of co2 build up as I work from home. It’s crazy how much better you feel, how much more productive your sleep is, and how much more productive your work is with fresh air! I wake up every morning before my alarm now feeling very refreshed. So odd how a small change has a huge impact on your quality of life.

          At over 2000ppm your cognitive skills can drop significantly – 40-95%, IIRC. What’s “safe” for humans is not necessarily what is good for humans.

          1. 1

            At our hackerspace we also have an automated system to turn fans on when CO2 levels reach a certain point. The previous location had https://revspace.nl/Spacesucker and the new space uses a different system (page is only in dutch) https://revspace.nl/Revfan

            Another interesting and cheap Co2 sensor is the MHZ19 ~ 16 euro from China or it seems ~ 30 euros from Amazon. https://revspace.nl/MHZ19

            1. 0

              There was a TED talk about a headquarters in New Delhi that installed the correct type and quantity of plants to achieve total “survive in a sealed glass bottle” homeostasis.

              I can’t seem to find a link from mobile right now (and I have no expertise to determine the scientific merit), but it led to my purchase and care of several “air purifier plants” that I’m happy to advocate for, if only for the benefits from more greenery in your work space.

              The three plants are Areca Palm, Mother-in-Law’s Tongue, and Money Plant.

              1. 3


                Unfortunately the talk contains bold claims on the effectiveness of those plants and is suspiciously lacking any verifiable source. Other sources seem to often be based on hearsay or non-replicated studies.

                1. 2

                  It’s bunk science. You can’t clean air in a building with plants. Requires far too many, and then you have to deal with all the co2 they release as well. And then ferns releasing spores… bad idea.

                  1. 1

                    Interesting, NASA also did a study about plants for cleaning air https://en.wikipedia.org/wiki/NASA_Clean_Air_Study

                    1. 2

                      That study was disproven by another NASA study, but that one is the only one people find in google search results :)

                      1. 1

                        Yes, and many sources keep quoting the same study. The fact that there is very little follow up research is odd. Also, the discussion here is about CO2 while the study is focused on [other] VOCs.

                    2. 1

                      Ah, that’s too bad. Thanks for sharing. If you do find any good sources on air purification, they’d be a good share here. I have a certified HEPA device, but I live close to a major highway in a dense urban environment, so even marginal improvements would be welcome.

                      1. 1

                        A HEPA filter? It might be the best option for particulate (if not too small) yet it does nothing for oxygen and CO2.