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Many indoor air quality sensor products are a scam

369 points by clairity 4y ago

genewitch 4y ago
i have a couple of no-name air quality sensors and they react to the environment fine, but they read high (like 500) CO2 outdoors. I got them in case CO2 was the reason for my spouse's insomnia. I've tested them by putting them in a large bowl with dry ice, and it certainly reacts to that. Also cooking makes the AQI number change dramatically. right now the powered one says my AQI is 2, CO2 is 515, CO is 9, HCHO is 18, and TVOC is 0.2. Neither of mine mention temp or humidity, and i've never taken them apart. I certainly won't rely on them to tell me if i actually have TVOC or HCHO issues. And i wish they had SD card slots that stored the values, like my 8 remote temp/humidity sensors and their base station.
Juliet245 4y ago
colechristensen 4y ago
Except for the sensor that straight up didn’t measure something it was reporting, “scam” is a strong word for inaccuracies.
jeffreygoesto 4y ago
Relative VOC measurements at least are able to detect a no. 2 in nappies. Great to distinguish if you should go in and change them or would be a distraction from falling to sleep when checking. I bulit a Pi ZeroW that measures on the side of the bed and publishes a curve of the last hour of the values. You can see a pretty salient drop when "it" happens.
- wil421 4y ago
  What sensor are you using? I bought a few trash ones from Microcenter. The readings were all over the place and I couldn’t get reliable numbers without smoothing numbers and throwing readings out. One of the spec sheets even said you would get crazy readings and would need to throw them out.
  - newman314 4y ago
    I'm a little surprised that no one has mentioned Aranet yet. From what I can tell, they appear to work quite well. However, it is quite pricey. I did look into the AirGradient when geerlingguy put out a video about it but they were out of stock at the time. It looks like there might be a new version but that may be something worth looking at. I tried the Vitalight CO2s but the readings were all over the place despite recalibration with 2 devices side by side. Ended up returning these. Do not recommend.
    - williamscales 4y ago
      yeah I was looking for mentions of Aranet. I have two and they came with calibration info iirc.
  - jeffreygoesto 4y ago
    I am using a Bosch BME680 and read it out with https://pypi.org/project/bme680/ https://pypi.org/project/bme680/
    - Rnonymous 4y ago
      This suffers from exactly what is mentioned in the article i assume. The temperature and humidity are thus unreliable.
      - jeffreygoesto 4y ago
        True. You need to know that and see if you can live with it for your use case. Some information is available at least, like the temperature coefficient of the pressure sensor [0]. Bosch offers an "interpretation library" that you also can train yourself specifically, that can be used for the successor BME688 [1]... [0] https://community.bosch-sensortec.com/t5/Knowledge-base/BME280-Sensor-Data-Interpretation/ta-p/13912 https://community.bosch-sensortec.com/t5/Knowledge-base/BME2... [1] https://github.com/BoschSensortec/BME68x-Sensor-API https://github.com/BoschSensortec/BME68x-Sensor-API
- myroon5 4y ago
  Why drop? Less gas afterwards?
  - qqqwerty 4y ago
    Maybe a voltage drop? Most sensors just return a voltage. And then you have to calibrate that value and convert it into some sort of measurement using an equation. So an increase in VOC might result in a drop in voltage on the sensor.
  - notduncansmith 4y ago
    It’s a relative indicator, so it would spike and then (relative to that spike) drop steadily as the VOCs diffuse and vent.
- clairity 4y ago
  yah, i think a lot of these IAQ (indoor air quality) products are ok at relative differences (which is mostly what lay consumers care about). the article mainly points out that they're not good at absolute measurements, and for something like VOCs, it's likely using a CO₂ sensor and a lookup table that's static and only really valid for the test room it was created in.
  - Majromax 4y ago
    > for something like VOCs, it's likely using a CO₂ sensor and a lookup table that's static and only really valid for the test room it was created in. It's the other way around, usually. CO₂ is more typically the estimated value, since its direct detection involves a relatively expensive NDIR value. VOCs as a category need some sort of modeling and estimation, but sensors can go fairly far by directly measuring a few species (hydrogen, for example), and hoping.
    - clairity 4y ago
      oh, right, dunno where that brain fart came from... thanks for the correction!
- slig 4y ago
  I bought a couple of Figaro TGS2602 from Aliexpress and they were quite sensitive to "human gas emissions".
- JTbane 4y ago
  Could you use this to detect flatulence in adults?
  - dpwm 4y ago
    If you were to have an array of such sensors, perhaps you'd be able to estimate direction of travel.
    - fghorow 4y ago
      Now there is a budding seismologist's answer! ;-)
    - checkyoursudo 4y ago
      "I'm sorry, Frank. The sensors don't lie. I'm going to have to ask you to leave."
  - odysseus 4y ago
    For sure. I have a couple of Winix air quality sensors / purifiers and they power up (with red LEDs and rushing fans) almost immediately if anyone has a little gas anywhere in the room.
    - entropic88 4y ago
      My kids call our winix purifiers "fart detectors"
  - IvyMike 4y ago
    DIY: https://projects.raspberrypi.org/en/projects/fart-detector https://projects.raspberrypi.org/en/projects/fart-detector
- kaybe 4y ago
  Nice, I'd be interested in a write-up with plots!
- SrslyJosh 4y ago
  I have an Awair sensor, and I can confirm that the VOC sensor is able to detect...well, pretty much anything from food to hair products to outgassing from some new thing that I opened up and accidentally left too close to the sensor.
  - tclancy 4y ago
    Yeah, I don’t know how good it actually is, but the one time I painted indoors the thing cratered in a way it never has before or since. And my daughter keeps trying to see if flatulence will actually drop the air quality depending on proximity.
  - rgbrenner 4y ago
    I got 3 awairs and they were all over the place sitting right next to each other.
ars 4y ago
And this is why I never bought one, even though I want one. I can't seem to find a reasonably priced one that is actually accurate.
- s0rce 4y ago
  PM2.5 have decent accuracy and are certainly useful at low price points, RH/temp work fine, particularly with separate sensors. Pressure works fine but is pretty useless. NDIR based CO2 (ex. Sensirion SCD31 or 41) also work fine. TOC is a bit of a mystery, it can probably detect relative change. I've used them in a lab to monitor solvent vapor and you can detect changes, hard to quantify but don't need to most of the time.
  - mrsteveman1 4y ago
    > NDIR based CO2 (ex. Sensirion SCD31 or 41) also work fine. SCD4x series are photoacoustic rather than NDIR, but they are true CO2 sensors and seem to work rather well given the size.
    - s0rce 4y ago
      I guess, yes and no. Technically the scd41 emits IR, it just doesn't detect transmitted light, instead sound produced by the CO2 that absorbed the light.
TylerE 4y ago
Seems like the best solution would be a two part enclosure... one for the sensor, with just enough to power it (e.g. a coin battery) and a Bluetooth LE transmitter (Or maybe even something entirely passive like RFID could work?) and then have all the rest of the electronics sealed off and powered seperately.
- advisedwang 4y ago
  Sadly you can't skip to engineering a solution. If you're designing a device getting quality requires rigorous specification and testing, in a feedback loop with design. What you describe might be a solution, but you can't know it's worked without that testing, and it's premature/risks over-engineering unless the testing shows you need it. It's the time and money of testing that is usually being skipped, not the engineering itself. (Although many manufacturers might sacrifice quality to save the cost of what you describe anyway :( )
zokier 4y ago
scam implies malicious intent. being crappy is not a scam.
- kqr 4y ago
  Intentionally manufacturing something with tolerances wide enough to be nearly useless and then selling it as if it was useful sounds malicious enough to me!
- incone123 4y ago
  The malice is in taking my money in exchange for a product the seller knows to be worthless.
  - aidenn0 4y ago
    GP was implying the seller didn't know it was worthless.
- IggleSniggle 4y ago
  Maybe so, but for the consumer is there any difference? If you say your product does a thing, and it definitely does NOT do that thing (but you fully believe it does that thing perhaps on the basis of believing really really really hard), and you sell it on the basis of that belief, especially when said belief is easily disproven with a tiny bit of due diligence… under those conditions I think it’s perfectly reasonable to call it a scam. Especially colloquially, when intent is near impossible to know, and the average consumer does not have the means to launch an investigation to prove intent.
  - NoPicklez 4y ago
    The "NOT do that thing" is the questionable part, lots of devices that measure things can claim to do so when they aren't "accurate". The difference is how inaccurate is the device and is the margin of error something that should be communicated. The classic example are scales, you can buy scales and weigh yourself on them and they might not be 100% accurate. But you can still sell a product that claims you can weigh yourself. Should we require standards that require companies to provide a +/- variance against exact measurements? Some products do such as power meters. If a product is outside of a particular variance then could we call those scam products?
e63f67dd-065b 4y ago
I recently bought a sensor that detects temp, humidity, PM2.5, PM10, and CO2, and the variance from the equivalent report from the airport's weather station that's only a few minutes away is discouraging even when it's set outdoors. Maybe I should bring it into my alma mater and borrow some lab equipment and test it out. At least the CO2 says 410 when set outdoors, but the temperature it varies by a few degrees (Celcius). The humidity is even worse, I don't even bother looking at that number anymore.
- wil421 4y ago
  The sensors I bought from Microcenter were garbage in the ways you describe. I couldn’t even take readings from some sensors because they were so ridiculous.
autoexec 4y ago
I'm still planning on buying a CO2 monitor, but I'm really not looking forward to it. My plan is to buy them three at a time and if I don't get the same reading (or damn near it) on all three returning them as defective and buying another three from some other random no-name Chinese manufacturer. I'm guessing the whole process is going to take many months and a lot of my time, and in the end it still can't prevent a company from just giving identical but incorrect readings.
- kzrdude 4y ago
  Could you calibrate vs outdoor atmosphere CO2 from a local weather station?
  - s0rce 4y ago
    You can just call outdoors 400ish, it doesn't vary hugely, or just take a bunch of measurements outdoors. Some sensors tend to zero offsets/drift periodically when they "detect" they are outside.
- briandrupieski 4y ago
  NDIR CO2 sensors are reasonably accurate. You can look up if the device is using an NDIR sensor before you buy it. Monitors that estimate CO2 based on a VOC sensor like mentioned in the article aren't using an NDIR sensor.
- sbierwagen 4y ago
  I built a CO2 meter around a SCD30 nondispersive infrared sensor a few years ago. (~$60) Gives readings with PPM resolution, which is good enough, since you're only going to start noticing physiological effects above 1000 PPM. As the article mentions, there is substantial sensor self-heating. (The SCD30 uses a little incandescent bulb to produce 4.26um light, and the whole package draws 375mW during measurement) It wants to be very well ventilated, or polled very infrequently, in order to remain anywhere near ambient.
  - s0rce 4y ago
site-packages1 4y ago
I have a few of the Airthings View Plus units. Can’t speak objectively but when there are fires or something degrading air quality, PM2.5 rises, when all windows and doors are closed, co2 rises and then falls when I open the windows and turn on the fan blowing the air out. VOCs rise can be correlated directly with the nest turning on our old AC unit and then with it turning off and fanning the air out the windows. Radon seems to rise with outdoor temperature when it gets hot out. One per floor of the house and they are all correlated with the things above, and the VOCs in the room with the most air conditioning blowing rise the most, so I feel pretty happy about their efficacy. I’ve been happy with these units so far after six months.
- RL_Quine 4y ago
  We got at least one which seems faulty, but to their credit they immediately got back to us and asked for more data for their engineering to look at. The numbers produced are obviously very very wrong. They seem solid otherwise and are accessible with open source tools.
  - InitialLastName 4y ago
    I notice their response wasn't "Your device appears to be faulty, here's an RMA shipping tag". You are giving them a lot of credit when it seems that "The numbers produced are obviously very very wrong" is the headline (by a large margin).
- sliken 4y ago
  Happy user here. I started with 2 of the BT connected widgets, that used my phone to upload to the cloud. I then added to the Airthing View Plus which does wifi, BT, and if you plug a cable in will act as a gateway from bluetooth to the airthings web service. Seems like a cool company, and have seen things like forest fires, using a gas stove, and burning things while cooking all correlate with readings. In particular I noticed that 3am in my bedroom has a pretty big CO2 spike. I also monitored radon before, during, and after some radon mitigation. I really like that at least some of their units allow exporting their data to graphana, without any cloud involvment. I'm unsure if the view plus does the same though. So for the HN crowd, lots of sensors, can use a raspberry pi as a gateway, your phone, or a turn key view plus. Graphana support is a big plus and you don't have to use any cloud service if you don't want to. I do wish they had a carbon monoxide sensor.
RivieraKid 4y ago
I'm just looking for an indoor air quality monitor for temperature, humidity, co2 and ideally pm2.5 and pressure. Can't believe such trivial product is so hard to find. There is the AirGradient DIY but I don't like the design, I'm worried about temperature accuracy and response time and I wish it was pluggable into a wall plug. In addition I want to buy an outdoor water-proof temperature and humidity sensor running on a battery and communicating over WiFi or BT. Also can't find anything.
- RL_Quine 4y ago
  https://www.airthings.com/en-ca/wave-plus https://www.airthings.com/en-ca/wave-plus These have worked well for us, they don't do pm2.5 but we have other sensors for that.
  - RivieraKid 4y ago
    View Plus looks like what I was looking for.
- toss1 4y ago
  >>such trivial product is so hard to find. Indeed! Although it seems the point of the article is that while these are very basic measurements, building the technology to reliably provide correct readings, especially from the same board/housing as a WiFi board, is not trivial. Sure, it's not as difficult as more complex or obscure devices, but it is a lot more than cut & paste some sensors onto a board with some WiFi & slap it in a box... which seems to be the usual level of effort Does anyone know where we could get such devices that 1) are actually designed to be reliable, and 2) don't need to exfiltrate information to the seller's servers in order for us to access it?
- TylerE 4y ago
  For the outdoor version, the magic search phrase is “personal weather station”.
- robga 4y ago
  I run 4 AirGradients with ESPhome hooked up to Home Assistant and couldn't be happier. In case you're not aware, the kit was upgraded this year to move the temperature sensor a little further away from heat sources, they now bundle enclosures with the kit (if requested), and also sell [0] pre-soldered kits. [0] https://www.airgradient.com/open-airgradient/shop/ https://www.airgradient.com/open-airgradient/shop/
com2kid 4y ago
My cheap co2 sensor shows dramatically different readings for my office with the window closed vs open. It is great at reminding me to crack my window open to get more air flow. Its temperature sensor is within a couple degrees of my nest's remote sensor. My Amazon vo2 sensor can tell if I turned my kitchen fan on to a sufficient level to clear out whatever I am cooking. Lots of sensors don't need to be precise, they just need to indicate if some action needs to be taken. e.g. If there is a fire, I just need the alarm to go off, I don't care how hot the fire is.
- cosentiyes 4y ago
  Agreed, as long as deltas are consistent I find the devices useful. I feel like fitness tracker step counts fall into the same category--I don't care much about the absolute number is, but rather how that changes over time and correlates with other behaviors.
- rufus_foreman 4y ago
  Exactly, the co2 sensor in my home office really only needs a few levels: Windows have been open with fans running for a while (~430) Windows have been closed for a short time (~700) Windows have been closed for a long time (~1200) Windows have been closed and someone has been cooking downstairs on the unvented gas stove (~4000)
- therealdrag0 4y ago
  I have an $80 monitor and it doesn’t seem trustworthy. It has very similar low values 90% of the time, barely ever correlated with forecast AQI I get online. And even when it was wildfire season and I walked out in the smoke (150 AQI) with it the values only bounced around a bit but still were <50 AQI 80% of the time and still <100 AQI the remaining time.
  - ksaj 4y ago
    I rather like the environment devices for Raspberry Pi. Surely they aren't "professional level," but for things like CO2 and other particles and gases, you can generate scrolling graphs. That lets you always know whether things are going up or down at any given moment. Most of the store-bought devices just beep if too high etc, but having a visible graph certainly tells you if it is measuring anything at all, and if you need to crack open a window or blow out the novel candle you just bought from the dollar store.
monopoliessuck 4y ago
We really just need a group like ConsumerReports, Labdoor, WireCutter or something that actually digs into the quality and claims of devices. Very few people are going to buy 30 competing options as well as a known good control and compare and contrast them in a scientific context, but that's what's needed. I remember looking around for a Radon sensor for way too long. An electronic device, a litmus-like strip test, some analog crystal ball -- hell a mail-in lab kit bag of carbon -- but they all seemed inaccurate. The few people that "bought two" always showed heavy variance while the majority that bought and got a number *loved it*. Even buying two that agree often just means the products are consistently and predictably wrong, but most products don't even check this box ffs. Reviewers that try and apples-to-apples all products by comparing cost, size, advertised features and ergonomics are doing no better than you or I opening up a package and appraising it. For awhile this Google dev was putting up extremely detailed amazon reviews for USBC cables based on their purported features v. reality and it was wonderful, but tucked away and undiscoverable. The world needs multiple parties providing unbiased in-depth reviews, but there's very little will to pay for even one group to do something like this. Ironically, paying for information in the information age seems almost comical to today's consumers and while there's demand for good information, no one's willing to open their wallets. Labdoor moved from subscription-only memberships to "certified products" and affiliate links because everyone wants to know what's in their multivitamin, but no one wants to pay for an indepth review. We aren't cultivating a supply-side that works for us, but against us. The result of this is shilling and fake reviews running wild. I mean hell, consumers will buy a product knowing full well they might get a shoddy knock off and yet it's $5 less and they can get it tomorrow so they'll roll the dice. Sadly, we don't live in a world where people are intimately concerned with quality and accuracy in their purchases. edit: USBC not USB3
- masklinn 4y ago
  > Reviewers that try and apples to apples all products by comparing cost, size, advertised features and ergonomics are doing no better than you or I opening up a package and appraising it. Unless you're buying every product on the market and load testing them in your garage, some folks do a lot better than that (e.g. project farm, or torque test channel). But it clearly requires time and passion, and serious rigs for some of the tests (not everybody has a Skidmore lying around).
bsder 4y ago
What a useless article. How about some evidence and pointers to things that aren't? Humidity/pressure/temperature are actually the three measurements that probably aren't a scam. The sensor chips you can get are generally well-calibrated and do what they say. Do read the datasheet, though: there are lots of ways you can screw them up (soldering them wrong, for example). The CO2, VOC and particulate sensors seem to be absolute snake oil, though. I have yet to buy any device that "senses" these that has any correlation to anything resembling reality. Which seems kind of stupid because CO2 and particulate sensors shouldn't be that difficult. Volatile organics, though, tend to be difficult as they have a lot of confounding factors. I'd really love to have a recommendation for something that's been validated that isn't $10K+.
- _yb2s 4y ago
  I agree... I have a bunch of cheap indoor air quality measuring devices, and they all consistently read temp, pressure, and humidity close together. My CO2 meter measures exactly what I'd expect -high levels with windows closed, correct outdoor levels with windows open. My cheap PM2.5 air quality meter reads almost exactly what I see in purple air when I take it outside. Basically, I purchased a bunch of diverse cheap air quality sensor products that I have verified all read correctly, and are not scams. I don't think this article is accurate.
- ThrowawayR2 4y ago
  Why not look at bare HVAC sensors used for office building air quality monitoring? - https://new.siemens.com/global/en/products/buildings/hvac/sensors/air-quality.html https://new.siemens.com/global/en/products/buildings/hvac/se... - https://buildings.honeywell.com/us/en/brands/our-brands/bms/field-devices/iaq-sensors https://buildings.honeywell.com/us/en/brands/our-brands/bms/... Granted, they're not meant for standalone use but at least you're not wondering whether the vendor is reputable or whether the sensor does what it says it does. For example, at a casual glance, the Siemens QPA2002D VOC and CO2 sensor seems to be available for <$500 and comes with a fairly comprehensive datasheet.
f1shy 4y ago
I've an airthings (https://shop.airthings.com/GB_EN/view-pollution.html https://shop.airthings.com/GB_EN/view-pollution.html) sensor, which measures a bunch of things. The pressure is constantly less than 1000 hPa (after 1 year of having the device, not once was higher (I live at 100 m msl) so it must be higher. When I reported the problem, the technical support said "we use Bosch Sensors, so it is impossible that they are wrong". Not only the service is trash, but also the whole interface, which requires permanent internet connection. You can access from your phone the status of the air at your home from anywhere in the world... my fear is if anybody else also can. Notably, after 1 year, there was no SW update... I really doubt the device is safe. I only have it because of Radon measurements. And I hope they are at least more or less ok.
- queuebert 4y ago
  I've compared my Airthings to a mail-in radon test kit, and they were consistent, for whatever that's worth.
s0rce 4y ago
The south coast AQMD has a great website testing various air quality (mostly pm2.5) in lab and real-world situations against equipment http://www.aqmd.gov/aq-spec http://www.aqmd.gov/aq-spec
runjake 4y ago
PurpleAir sensors are pretty good, according to the scientists I’ve talked to (n=3). The outdoor models work inside or out.
- S201 4y ago
  They do! Although they require a correction factor to better match the government's fancy air quality monitors when measuring smoke. The EPA published a paper on it: https://github.com/shanet/ClearAir/blob/master/docs/PurpleAir%20PM2.5%20Correction%20and%20Performance%20During%20Smoke%20Events.pdf https://github.com/shanet/ClearAir/blob/master/docs/PurpleAi... While we're on the topic: Shamless plug for a PurpleAir clone I made last year that uses the same sensors but at half the cost (and keeps all of the data within your LAN): https://github.com/shanet/ClearAir https://github.com/shanet/ClearAir and https://www.digikey.com/en/products/detail/adafruit-industries-llc/4632/12715744 https://www.digikey.com/en/products/detail/adafruit-industri...
  - runjake 4y ago
    So fantastic, thanks for the reply!
everyone 4y ago
I have seen some comments about air quality and particle counts here that I simply did not understand.. I live in a remote spot in the country in Ireland. I am surrounded by dairy farms (fields of grass with cows) I always have my windows open, all day all year round, though my room is super messy. People who know about this stuff, do you reckon I have good air quality?
- megous 4y ago
  Depends on how you/your neighbors produce heat if they are anywhere near. Villages' air can be pretty disgusting especially in colder months. Paradoxically, small cities when heated by remote heat can be quite enjoyable air quality wise all year round if you don't live near the main road.
yread 4y ago
I wonder when will personal CO2 scrubbers become a norm. With atmospheric CO2 growing ever higher and everyone having a CO2 detector (and an air "purifier") at home it's the next step.
- genewitch 4y ago
  you mean... plants? plants scrub CO2.
  - kolinko 4y ago
    Plants scrubbing co2 indoors are pure placebo. You would need to convert half of your apartament with a tropical jungle to offset what you breathe out. They look pretty, though.
- gsich 4y ago
  Probably never. 1000ppm seems to be a value where the concentration has some negative effects.
2OEH8eoCRo0 4y ago
I agree with you but for most things it honestly doesn't matter. The time you wasted researching is worth more than whatever difference there might be. I also think we don't need any of this junk in the first place. Indoor air quality? Open a window. airnow.gov
- mdp2021 4y ago
  Economics is based on trade-offs, and a trade-off of "opening windows" can be "lowering indoor temperature". Incidentally: some parts of the world are in an energy crisis. Edit: also, that «whatever difference» clashes pretty heavily with > It is hilariously easy to inadvertently design a device that measures temperature with an error of 5degC, humidity error of 50% and pressure error of equivalent to 1km in altitude It is also difficult to avoid noting that we "look into things" for many reasons and also indirect gains; that there exist "silent killers" and, more importantly to some, silent harmers; that some "principle of inquiry" (of "knowing the world", of testing, like Galileo's "Saggiatore") and a "principle of wanting to get things done properly" are there...
ahaucnx 4y ago
Great article and I mostly agree. We launched our indoor air quality monitor AirGradient ONE at the beginning of this year. We measure PM, CO2, TVOCs, temperature and humidity. When we started the development we would have never thought that achieving an accurate temperature measurement was by far the most difficult thing. It took us 8 hardware iterations to get it right! We experienced with different enclsoure shapes, orientations and PCBs (component placement). Our experience is similar to the author of this article: Your biggest enemy is internal heat produced by active components, mainly the MCU but also by other sensors like the PM sensor and CO2 (NDIR). How we solved it: 1) Minimize heat from energy by using components that have low energy consumption and make extensive use of sleep functions of the MCU as well as sensor components (e.g. PM sensors can be put to sleep). 2) Make use of physics. Our monitor is wall mounted and uses the convection mechanism. So nearly all components that heat up like LEDs, MCU etc. are located at the very top inside the enclosure. Optimize the vents at the top and bottom of the enclosure and create an unobstructed air flow through the enclosure based on natural convection. 3) Plan for enough space. To get temperature right, you need a lot of air around the temperature sensor that is free from radiation from other heat sources. So we specifically designed the PCB to have the temperature sensor at a 'finger' at the bottom with a lot of space to other components and ensured there is a good air flow around. If you are interested to see our design, have a look at our open-source, open-hardware DIY Pro monitor [1]. We integrated a lot of the things we learned designing the commercial monitor mentioned above into these build instructions [2] that allow you to build your own highly accurate monitor and then also be able to change the firmware and adjust to your needs. In fact, our kit contains exactly the same plastic injected enclosure we use for our commercial monitor (but you can also just 3D print the one from the build instructions and get the other parts by yourself). [1] https://www.airgradient.com/open-airgradient/kits/ https://www.airgradient.com/open-airgradient/kits/ [2] https://www.airgradient.com/open-airgradient/instructions/diy-pro/ https://www.airgradient.com/open-airgradient/instructions/di...
- matheweis 4y ago
  What about outdoor pm2.5? I live in an area prone to frequent fog for many months out of the year. I learned that the fog will thoroughly disrupt the accuracy of pm2.5 sensors. After some research I found that running the air through a heated pitot or similar before taking a measurement will almost entirely correct this for somewhat obvious reasons; the fog is evaporated. As far as I can tell, none of the mid to high range weather stations have such a system and they will all be corrupted by a sight fog. I’ve resigned myself to making one… Does such a sensor even exist?
Maursault 4y ago
I bought a couple of expensive remote weather sensors because they were the only ones I could find that included sensing atmospheric pressure and wet bulb temperature along with the ordinary metrics like temperature and humidity. Though air quality and particulate count is not included, I have done without for two reasons, which is that I live in the country surrounded by water and forest and cleaner air than I have ever known, and in contrast, the small house is old, dusty, I can easily see the particulates floating in the air, and because I know it is bad, I just don't need to know any precise measurements. My only complaint concerning the devices, which seem to be rugged and accurate, though with an almost absurd accompanying price tag, is that the required app and its interface design is comically bad in every measure that could matter. If there are interested developers, please take a look at the product[1] and the software[2], and see if you're interested in developing and selling me and other customers, and perhaps even the manufacturer, an application that collects and displays data from this family of devices that doesn't completely and utterly suck. [1] https://kestrelmeters.com/products/kestrel-fire-weather-drop https://kestrelmeters.com/products/kestrel-fire-weather-drop [2] https://apps.apple.com/us/app/kestrel-link/id1489485544 https://apps.apple.com/us/app/kestrel-link/id1489485544
- z9znz 4y ago
  Indoor air quality can be greatly affected by all kinds of things in your home, from the building materials to the paints, coverings, veneers, veneer glues, fabrics, etc. etc. etc. So in other words, while your outside air may be quite good such that it doesn't negatively affect your indoor air quality, that does not at all suggest that your indoor air quality will be good.
  - Maursault 4y ago
    I know, and I know it's bad in there, but knowing precisely how bad is not useful information. A week away and there's a film of dust on everything. Most places, the dust is human skin, but not here. I think it's the old veneer covering the cinderblock walls and the cinderblock. Place was built in the 1940's, and it is slowly deteriorating particle by particle. But the rent is cheap. I have a HEPA filter on a box fan for the bedroom that runs constantly, which I hope helps, and I spend my days outside.
dawnerd 4y ago
I bought an aranet4 which is excellent for co2 but it doesn't do pm or vo2. I can however infer that if the co2 is high I need to ventilate anyways. Crazy to see how high co2 rises on flights that are supposedly "refreshing air" often.
londons_explore 4y ago
I bought ~5 brands of air temperature sensor, and was surprised to find that when I left them in a sealed box overnight, every single one showed the same temperature to 0.1C. I was expecting them to have at least 10x that error!
- ahaucnx 4y ago
  The sensor modules are often not the problem. It is the heat radiation from other components in the enclosure that influence the temperature.
- askvictor 4y ago
  It's really easy to calibrate a temperature sensor.
EVa5I7bHFq9mnYK 4y ago
I see "wi fi connected" seems like a default choice now, not even questioning. I had one such CO2 detector, but then I realized that anyone gaining access to it (any employee of the manufacturer, for example) can know exactly when we are at home, when we are not, when we go to bed, when we go on vacation etc. So I disconnected it, bought a $70 device that measures everything pretty accurately and am happy ever since.
- therealdrag0 4y ago
  Which 70$ device? I also have one in that range and I don’t trust it.
  - EVa5I7bHFq9mnYK 4y ago
    It's called Dienmern model DM72B, from Aliexpress, I compared its temperature, humidity and CO2 measurements with other devices and found them correct; as for PM2.5, HCHO and TVOC, I didn't calibrate, but they seem reasonable and detect smoke/farts immediately.
- walterbell 4y ago
  Would appreciate recommendation on non-WiFi sensor.
  - EVa5I7bHFq9mnYK 4y ago
    Dienmern model DM72B, from Aliexpress
outworlder 4y ago
I wonder if a DIY version would fare better on their testing? Something like: https://www.airgradient.com/open-airgradient/instructions/diy/ https://www.airgradient.com/open-airgradient/instructions/di... I have bought all the parts, haven't had the time to assemble it yet.
- ahaucnx 4y ago
  Our old basic kit that you link above has also temperature inaccuracies due to its small footprint but we have a new kit that addresses these issues and is also available as a pre-soldered version for easy assembly: https://www.airgradient.com/open-airgradient/instructions/diy-pro/ https://www.airgradient.com/open-airgradient/instructions/di...
deleted 4y ago
[deleted]
LorenPechtel 4y ago
It's not just air quality sensors. Got some wifi thermostats some years back. Oops--they draw too much power. At least it's consistent, we set them two degrees above what we actually want and and they work fine. And we also have an example of the problem of air circulation. We have a wireless thermometer (a quick check if it's cool enough to open the windows) that's in a weather enclosure that admits a decent amount of air and sitting under a tree (keeping it out of the sun and away from big masses of concrete--it's simply impossible to properly place it in our yard) and it can be up to two degrees off because of lag.
Mountain_Skies 4y ago
I purchased a 'Yvelines' brand air quality monitor. The company appears to be one of those random word Chinese generic product companies. Some of the readings spike when I take the unit into the garage where we park the cars, keep the lawnmower, gas can, etc. Most go down if I take the unit outside. I don't know how accurate the numbers actually are but it certainly can distinguish between areas with different levels of pollutants.
xani_ 4y ago
> I once saw a sensor chip that claimed to measure both CO2 and TVOC (total volatile organic compounds). After finding some further documents on the part I discovered it was a total scam. It only actually measured one of those things, then it used this measurement to look up an expected value of the other in a table the manufacturer made based off “common indoor measurements”. I remember similar thing with some UVC sensors, they just returned expected UVC based on UVA level
dalanmiller 4y ago
I'm looking for a comprehensive air quality measurement gadget for different rooms in my home. What devices are people using that aren't a _complete_ sham?
- mrspuratic 4y ago
  I got an Aprotii "7-in-1" sensor from Amazon UK for about €120 ("currently unavailable"). I haven't seen the same device from other vendors, which is unusual for this type of device on Amazon. Claims to be NDIR, can't seem to open it without trashing the glued down screen cover, so I haven't. I'm no expert on this type of device, I just figured anything less that €50 was going to be pointless. Lots of ventilation holes on 5 sides, a screen you can read from 8m away. Agrees (within tolerance) of a nearby temp/humid sensor. CO2 and VOC are independent. CO2 alone goes up during the day if I don't crack a window, VOC varies with how hot and close beverages are. PMs/VOC are mostly a function of how badly my cooking went in the adjacent kitchen :) I can't be certain about absolute accuracy of values, temp/humid are good, CO2 seems plausible: low is 400ppm, I start to get cranky while working by about 1200ppm. It's wifi (Tuya) if you want, the screen and controls alone are fine though. It also has RS485 and a bunch of relays to drive A/C, Fan, (de)humdifier too. There's a Spanish report that links Kkmoon/Kecheer/Curconsa/Aprotii device vendors: F. Villanueva, E. Jiménez, J. M. Felisi, T. Garrido, J. L. Jiménez, M. Ródenas, and A. Muñoz. Guide about affordable CO2 detectors for COVID-19 Prevention, versión 1.4, 17/04/2021. https://bit.ly/monitorsCO2 https://bit.ly/monitorsCO2 HTH.
QuantumGood 4y ago
Also home blood pressure monitors.
ck2 4y ago
So these are fake/inaccurate? That's a shame because I wanted to build one someday - but also they sell them to schools for CO2 monitoring? https://www.airgradient.com/open-airgradient/shop/ https://www.airgradient.com/open-airgradient/shop/ also previously on HN: https://news.ycombinator.com/item?id=28457135 https://news.ycombinator.com/item?id=28457135 > Monitoring my home's air quality (CO2, PM2.5, Temp/Humidity) with AirGradient's DIY sensor September 8, 2021 > A few months ago, I found this Hacker News post about the AirGradient DIY Air Quality Monitor. I had already been considering buying an AirThings Wave Plus sensor to monitor my home's CO2 levels, but the high price and limited 'ownership' of the data coming from it turned me off. also > AirGradient: DIY Air Quality Monitoring with Open-Source Hardware & Firmware https://news.ycombinator.com/item?id=27124671 https://news.ycombinator.com/item?id=27124671 https://www.airgradient.com/open-airgradient/instructions/diy/ https://www.airgradient.com/open-airgradient/instructions/di...
palisade 4y ago
I own an IQAir AirVisual Pro, it has identified when the air from ovens affect air quality. And, I bought a Honeywell HPA300 True HEPA Air Purifier and you can see air quality improve significantly when it is on. Also, when a large group of guests come over the CO2 monitor accurately tracks the large increase. And, it detected when Elon's factories had their fires. In addition, anytime there were forest fires in California it detected the increased pollution from those as well. The air quality several states away is affected by those fires severely btw, pretty interesting. The smoke plumes travel all the way to Maine. I've been pretty happy with both products. When the air quality drops outside, I close the doors and windows and let the air purifier do its magic. I leave the HPA300 on "Germ" mode, it is pretty quiet and still gets the job done.
Thaxll 4y ago
If you want high quality usb sensors: https://www.yoctopuce.com/EN/products/category/usb-environmental-sensors https://www.yoctopuce.com/EN/products/category/usb-environme...
neves 4y ago
IV bought one from Ali express that is a piece of garbage
mdp2021 4y ago
> most of my reviews would be worth dirt a month after publishing when either the items go out of stock or get their insides silently changed Very sad reality, from clothes to electronics. One wonders whether this run for cheaper builds while remaining relatively conservative in prices, unrestrained by a - missing - critical mass of discerning, demanding consumers, will end through some fading of the economic causes that triggered it. Or if this culturally polluting trend will stick now that it has been installed as a "normalcy".
- mdp2021 4y ago
  (Since I see that this is this quite alive: Update: real time: I have just been told in a shoestore, "No, forget about the good quality you could find years ago: it is either "meh" shoes or shoeless". I mean, I have good hope that if one made of finding good products a job in itself, with extensive effort, some reservoir may eventually be found, but really this whole situation is /very/ suboptimal.)
kimi 4y ago
AirSensEUR is an open framework focused on air quality monitoring using low cost sensors. The project started on 2014 from a group of passionate researchers and engineers. The framework is composed by a set of electronic boards, firmware, and several software applications. https://airsenseur.org/website/airsenseur-air-quality-monitoring-open-framework/ https://airsenseur.org/website/airsenseur-air-quality-monito...
Semaphor 4y ago
I don’t currently have air quality measurements, but I do have Aqara (not Wifi but Zigbee) temperature and humidity sensors. Zigbee uses less energy (afaik?) than WiFi or BT, and additionally, while there is no arrow, the symbol shows you which way is up, and it fits with the description (ventilation holes at the top). From what I’m reading, the fact that several sensors measure almost exactly the same values when mounted next to each other, is actually a good sign, correct?
- kapep 4y ago
  I have Aqara WSDCGQ11LM sensors which only have small holes for the sensor at the bottom but no ventilation holes for the main part of the board. At the bottom of the product page [1] they have an explosion graphic rendering which looks like (assuming it is somewhat correct) the sensor is below other chips and moved away from them. The sensor also seems to be shielded by having a separate area of it's own in the plastic enclosure. I haven't tested them yet but I think they should do fine, by the criteria of the article. - [1]: https://www.aqara.com/us/temperature_humidity_sensor.html https://www.aqara.com/us/temperature_humidity_sensor.html
specialist 4y ago
Teardowns as the new product reviews. Consumer Reports meets iFixit meets Twitch hybrid would be awesome. Plus the objective repeatability of Jepsen and TechEmpower. Some magical combination of authenticity, expertise, tenacity and personal narrative. As a noob DIY remodeler, I learned SO MUCH from channels like Project Farm, Matt Risling's The Build Show, Vancouver Carpenter, and others. For whatever reason, I didn't get nearly as much from content tailored to prior mediums, like This Old House and misc handy person magazines. (Probably some McLuhanian "medium is the message" insight applies...)
sizzle 4y ago
I have a senseair s8(?) that uses ladder to measure CO2 Can anybody tell me how reliable and accurate this sensor is?

369 points by clairity 4y ago

i have a couple of no-name air quality sensors and they react to the environment fine, but they read high (like 500) CO2 outdoors. I got them in case CO2 was the reason for my spouse's insomnia. I've tested them by putting them in a large bowl with dry ice, and it certainly reacts to that. Also cooking makes the AQI number change dramatically. right now the powered one says my AQI is 2, CO2 is 515, CO is 9, HCHO is 18, and TVOC is 0.2. Neither of mine mention temp or humidity, and i've never taken them apart. I certainly won't rely on them to tell me if i actually have TVOC or HCHO issues. And i wish they had SD card slots that stored the values, like my 8 remote temp/humidity sensors and their base station.

Juliet245 4y ago

colechristensen 4y ago

Except for the sensor that straight up didn’t measure something it was reporting, “scam” is a strong word for inaccuracies.

jeffreygoesto 4y ago

Relative VOC measurements at least are able to detect a no. 2 in nappies. Great to distinguish if you should go in and change them or would be a distraction from falling to sleep when checking. I bulit a Pi ZeroW that measures on the side of the bed and publishes a curve of the last hour of the values. You can see a pretty salient drop when "it" happens.

wil421 4y ago
What sensor are you using? I bought a few trash ones from Microcenter. The readings were all over the place and I couldn’t get reliable numbers without smoothing numbers and throwing readings out. One of the spec sheets even said you would get crazy readings and would need to throw them out.
- newman314 4y ago
  I'm a little surprised that no one has mentioned Aranet yet. From what I can tell, they appear to work quite well. However, it is quite pricey. I did look into the AirGradient when geerlingguy put out a video about it but they were out of stock at the time. It looks like there might be a new version but that may be something worth looking at. I tried the Vitalight CO2s but the readings were all over the place despite recalibration with 2 devices side by side. Ended up returning these. Do not recommend.
  - williamscales 4y ago
    yeah I was looking for mentions of Aranet. I have two and they came with calibration info iirc.
- jeffreygoesto 4y ago
  I am using a Bosch BME680 and read it out with https://pypi.org/project/bme680/ https://pypi.org/project/bme680/
  - Rnonymous 4y ago
    This suffers from exactly what is mentioned in the article i assume. The temperature and humidity are thus unreliable.
    - jeffreygoesto 4y ago
      True. You need to know that and see if you can live with it for your use case. Some information is available at least, like the temperature coefficient of the pressure sensor [0]. Bosch offers an "interpretation library" that you also can train yourself specifically, that can be used for the successor BME688 [1]... [0] https://community.bosch-sensortec.com/t5/Knowledge-base/BME280-Sensor-Data-Interpretation/ta-p/13912 https://community.bosch-sensortec.com/t5/Knowledge-base/BME2... [1] https://github.com/BoschSensortec/BME68x-Sensor-API https://github.com/BoschSensortec/BME68x-Sensor-API
myroon5 4y ago
Why drop? Less gas afterwards?
- qqqwerty 4y ago
  Maybe a voltage drop? Most sensors just return a voltage. And then you have to calibrate that value and convert it into some sort of measurement using an equation. So an increase in VOC might result in a drop in voltage on the sensor.
- notduncansmith 4y ago
  It’s a relative indicator, so it would spike and then (relative to that spike) drop steadily as the VOCs diffuse and vent.
clairity 4y ago
yah, i think a lot of these IAQ (indoor air quality) products are ok at relative differences (which is mostly what lay consumers care about). the article mainly points out that they're not good at absolute measurements, and for something like VOCs, it's likely using a CO₂ sensor and a lookup table that's static and only really valid for the test room it was created in.
- Majromax 4y ago
  > for something like VOCs, it's likely using a CO₂ sensor and a lookup table that's static and only really valid for the test room it was created in. It's the other way around, usually. CO₂ is more typically the estimated value, since its direct detection involves a relatively expensive NDIR value. VOCs as a category need some sort of modeling and estimation, but sensors can go fairly far by directly measuring a few species (hydrogen, for example), and hoping.
  - clairity 4y ago
    oh, right, dunno where that brain fart came from... thanks for the correction!
slig 4y ago
I bought a couple of Figaro TGS2602 from Aliexpress and they were quite sensitive to "human gas emissions".
JTbane 4y ago
Could you use this to detect flatulence in adults?
- dpwm 4y ago
  If you were to have an array of such sensors, perhaps you'd be able to estimate direction of travel.
  - fghorow 4y ago
    Now there is a budding seismologist's answer! ;-)
  - checkyoursudo 4y ago
    "I'm sorry, Frank. The sensors don't lie. I'm going to have to ask you to leave."
- odysseus 4y ago
  For sure. I have a couple of Winix air quality sensors / purifiers and they power up (with red LEDs and rushing fans) almost immediately if anyone has a little gas anywhere in the room.
  - entropic88 4y ago
    My kids call our winix purifiers "fart detectors"
- IvyMike 4y ago
  DIY: https://projects.raspberrypi.org/en/projects/fart-detector https://projects.raspberrypi.org/en/projects/fart-detector
kaybe 4y ago
Nice, I'd be interested in a write-up with plots!
SrslyJosh 4y ago
I have an Awair sensor, and I can confirm that the VOC sensor is able to detect...well, pretty much anything from food to hair products to outgassing from some new thing that I opened up and accidentally left too close to the sensor.
- tclancy 4y ago
  Yeah, I don’t know how good it actually is, but the one time I painted indoors the thing cratered in a way it never has before or since. And my daughter keeps trying to see if flatulence will actually drop the air quality depending on proximity.
- rgbrenner 4y ago
  I got 3 awairs and they were all over the place sitting right next to each other.

ars 4y ago

And this is why I never bought one, even though I want one. I can't seem to find a reasonably priced one that is actually accurate.

s0rce 4y ago
PM2.5 have decent accuracy and are certainly useful at low price points, RH/temp work fine, particularly with separate sensors. Pressure works fine but is pretty useless. NDIR based CO2 (ex. Sensirion SCD31 or 41) also work fine. TOC is a bit of a mystery, it can probably detect relative change. I've used them in a lab to monitor solvent vapor and you can detect changes, hard to quantify but don't need to most of the time.
- mrsteveman1 4y ago
  > NDIR based CO2 (ex. Sensirion SCD31 or 41) also work fine. SCD4x series are photoacoustic rather than NDIR, but they are true CO2 sensors and seem to work rather well given the size.
  - s0rce 4y ago
    I guess, yes and no. Technically the scd41 emits IR, it just doesn't detect transmitted light, instead sound produced by the CO2 that absorbed the light.

TylerE 4y ago

Seems like the best solution would be a two part enclosure... one for the sensor, with just enough to power it (e.g. a coin battery) and a Bluetooth LE transmitter (Or maybe even something entirely passive like RFID could work?) and then have all the rest of the electronics sealed off and powered seperately.

advisedwang 4y ago
Sadly you can't skip to engineering a solution. If you're designing a device getting quality requires rigorous specification and testing, in a feedback loop with design. What you describe might be a solution, but you can't know it's worked without that testing, and it's premature/risks over-engineering unless the testing shows you need it. It's the time and money of testing that is usually being skipped, not the engineering itself. (Although many manufacturers might sacrifice quality to save the cost of what you describe anyway :( )

zokier 4y ago

scam implies malicious intent. being crappy is not a scam.

kqr 4y ago
Intentionally manufacturing something with tolerances wide enough to be nearly useless and then selling it as if it was useful sounds malicious enough to me!
incone123 4y ago
The malice is in taking my money in exchange for a product the seller knows to be worthless.
- aidenn0 4y ago
  GP was implying the seller didn't know it was worthless.
IggleSniggle 4y ago
Maybe so, but for the consumer is there any difference? If you say your product does a thing, and it definitely does NOT do that thing (but you fully believe it does that thing perhaps on the basis of believing really really really hard), and you sell it on the basis of that belief, especially when said belief is easily disproven with a tiny bit of due diligence… under those conditions I think it’s perfectly reasonable to call it a scam. Especially colloquially, when intent is near impossible to know, and the average consumer does not have the means to launch an investigation to prove intent.
- NoPicklez 4y ago
  The "NOT do that thing" is the questionable part, lots of devices that measure things can claim to do so when they aren't "accurate". The difference is how inaccurate is the device and is the margin of error something that should be communicated. The classic example are scales, you can buy scales and weigh yourself on them and they might not be 100% accurate. But you can still sell a product that claims you can weigh yourself. Should we require standards that require companies to provide a +/- variance against exact measurements? Some products do such as power meters. If a product is outside of a particular variance then could we call those scam products?

e63f67dd-065b 4y ago

I recently bought a sensor that detects temp, humidity, PM2.5, PM10, and CO2, and the variance from the equivalent report from the airport's weather station that's only a few minutes away is discouraging even when it's set outdoors. Maybe I should bring it into my alma mater and borrow some lab equipment and test it out. At least the CO2 says 410 when set outdoors, but the temperature it varies by a few degrees (Celcius). The humidity is even worse, I don't even bother looking at that number anymore.

wil421 4y ago
The sensors I bought from Microcenter were garbage in the ways you describe. I couldn’t even take readings from some sensors because they were so ridiculous.

autoexec 4y ago

I'm still planning on buying a CO2 monitor, but I'm really not looking forward to it. My plan is to buy them three at a time and if I don't get the same reading (or damn near it) on all three returning them as defective and buying another three from some other random no-name Chinese manufacturer. I'm guessing the whole process is going to take many months and a lot of my time, and in the end it still can't prevent a company from just giving identical but incorrect readings.

kzrdude 4y ago
Could you calibrate vs outdoor atmosphere CO2 from a local weather station?
- s0rce 4y ago
  You can just call outdoors 400ish, it doesn't vary hugely, or just take a bunch of measurements outdoors. Some sensors tend to zero offsets/drift periodically when they "detect" they are outside.
briandrupieski 4y ago
NDIR CO2 sensors are reasonably accurate. You can look up if the device is using an NDIR sensor before you buy it. Monitors that estimate CO2 based on a VOC sensor like mentioned in the article aren't using an NDIR sensor.
sbierwagen 4y ago
I built a CO2 meter around a SCD30 nondispersive infrared sensor a few years ago. (~$60) Gives readings with PPM resolution, which is good enough, since you're only going to start noticing physiological effects above 1000 PPM. As the article mentions, there is substantial sensor self-heating. (The SCD30 uses a little incandescent bulb to produce 4.26um light, and the whole package draws 375mW during measurement) It wants to be very well ventilated, or polled very infrequently, in order to remain anywhere near ambient.
- s0rce 4y ago

site-packages1 4y ago

I have a few of the Airthings View Plus units. Can’t speak objectively but when there are fires or something degrading air quality, PM2.5 rises, when all windows and doors are closed, co2 rises and then falls when I open the windows and turn on the fan blowing the air out. VOCs rise can be correlated directly with the nest turning on our old AC unit and then with it turning off and fanning the air out the windows. Radon seems to rise with outdoor temperature when it gets hot out. One per floor of the house and they are all correlated with the things above, and the VOCs in the room with the most air conditioning blowing rise the most, so I feel pretty happy about their efficacy. I’ve been happy with these units so far after six months.

RL_Quine 4y ago
We got at least one which seems faulty, but to their credit they immediately got back to us and asked for more data for their engineering to look at. The numbers produced are obviously very very wrong. They seem solid otherwise and are accessible with open source tools.
- InitialLastName 4y ago
  I notice their response wasn't "Your device appears to be faulty, here's an RMA shipping tag". You are giving them a lot of credit when it seems that "The numbers produced are obviously very very wrong" is the headline (by a large margin).
sliken 4y ago
Happy user here. I started with 2 of the BT connected widgets, that used my phone to upload to the cloud. I then added to the Airthing View Plus which does wifi, BT, and if you plug a cable in will act as a gateway from bluetooth to the airthings web service. Seems like a cool company, and have seen things like forest fires, using a gas stove, and burning things while cooking all correlate with readings. In particular I noticed that 3am in my bedroom has a pretty big CO2 spike. I also monitored radon before, during, and after some radon mitigation. I really like that at least some of their units allow exporting their data to graphana, without any cloud involvment. I'm unsure if the view plus does the same though. So for the HN crowd, lots of sensors, can use a raspberry pi as a gateway, your phone, or a turn key view plus. Graphana support is a big plus and you don't have to use any cloud service if you don't want to. I do wish they had a carbon monoxide sensor.

RivieraKid 4y ago

I'm just looking for an indoor air quality monitor for temperature, humidity, co2 and ideally pm2.5 and pressure. Can't believe such trivial product is so hard to find. There is the AirGradient DIY but I don't like the design, I'm worried about temperature accuracy and response time and I wish it was pluggable into a wall plug. In addition I want to buy an outdoor water-proof temperature and humidity sensor running on a battery and communicating over WiFi or BT. Also can't find anything.

RL_Quine 4y ago
https://www.airthings.com/en-ca/wave-plus https://www.airthings.com/en-ca/wave-plus These have worked well for us, they don't do pm2.5 but we have other sensors for that.
- RivieraKid 4y ago
  View Plus looks like what I was looking for.
toss1 4y ago
>>such trivial product is so hard to find. Indeed! Although it seems the point of the article is that while these are very basic measurements, building the technology to reliably provide correct readings, especially from the same board/housing as a WiFi board, is not trivial. Sure, it's not as difficult as more complex or obscure devices, but it is a lot more than cut & paste some sensors onto a board with some WiFi & slap it in a box... which seems to be the usual level of effort Does anyone know where we could get such devices that 1) are actually designed to be reliable, and 2) don't need to exfiltrate information to the seller's servers in order for us to access it?
TylerE 4y ago
For the outdoor version, the magic search phrase is “personal weather station”.
robga 4y ago
I run 4 AirGradients with ESPhome hooked up to Home Assistant and couldn't be happier. In case you're not aware, the kit was upgraded this year to move the temperature sensor a little further away from heat sources, they now bundle enclosures with the kit (if requested), and also sell [0] pre-soldered kits. [0] https://www.airgradient.com/open-airgradient/shop/ https://www.airgradient.com/open-airgradient/shop/

com2kid 4y ago

My cheap co2 sensor shows dramatically different readings for my office with the window closed vs open. It is great at reminding me to crack my window open to get more air flow. Its temperature sensor is within a couple degrees of my nest's remote sensor. My Amazon vo2 sensor can tell if I turned my kitchen fan on to a sufficient level to clear out whatever I am cooking. Lots of sensors don't need to be precise, they just need to indicate if some action needs to be taken. e.g. If there is a fire, I just need the alarm to go off, I don't care how hot the fire is.

cosentiyes 4y ago
Agreed, as long as deltas are consistent I find the devices useful. I feel like fitness tracker step counts fall into the same category--I don't care much about the absolute number is, but rather how that changes over time and correlates with other behaviors.
rufus_foreman 4y ago
Exactly, the co2 sensor in my home office really only needs a few levels: Windows have been open with fans running for a while (~430) Windows have been closed for a short time (~700) Windows have been closed for a long time (~1200) Windows have been closed and someone has been cooking downstairs on the unvented gas stove (~4000)
therealdrag0 4y ago
I have an $80 monitor and it doesn’t seem trustworthy. It has very similar low values 90% of the time, barely ever correlated with forecast AQI I get online. And even when it was wildfire season and I walked out in the smoke (150 AQI) with it the values only bounced around a bit but still were <50 AQI 80% of the time and still <100 AQI the remaining time.
- ksaj 4y ago
  I rather like the environment devices for Raspberry Pi. Surely they aren't "professional level," but for things like CO2 and other particles and gases, you can generate scrolling graphs. That lets you always know whether things are going up or down at any given moment. Most of the store-bought devices just beep if too high etc, but having a visible graph certainly tells you if it is measuring anything at all, and if you need to crack open a window or blow out the novel candle you just bought from the dollar store.

monopoliessuck 4y ago

We really just need a group like ConsumerReports, Labdoor, WireCutter or something that actually digs into the quality and claims of devices. Very few people are going to buy 30 competing options as well as a known good control and compare and contrast them in a scientific context, but that's what's needed. I remember looking around for a Radon sensor for way too long. An electronic device, a litmus-like strip test, some analog crystal ball -- hell a mail-in lab kit bag of carbon -- but they all seemed inaccurate. The few people that "bought two" always showed heavy variance while the majority that bought and got a number *loved it*. Even buying two that agree often just means the products are consistently and predictably wrong, but most products don't even check this box ffs. Reviewers that try and apples-to-apples all products by comparing cost, size, advertised features and ergonomics are doing no better than you or I opening up a package and appraising it. For awhile this Google dev was putting up extremely detailed amazon reviews for USBC cables based on their purported features v. reality and it was wonderful, but tucked away and undiscoverable. The world needs multiple parties providing unbiased in-depth reviews, but there's very little will to pay for even one group to do something like this. Ironically, paying for information in the information age seems almost comical to today's consumers and while there's demand for good information, no one's willing to open their wallets. Labdoor moved from subscription-only memberships to "certified products" and affiliate links because everyone wants to know what's in their multivitamin, but no one wants to pay for an indepth review. We aren't cultivating a supply-side that works for us, but against us. The result of this is shilling and fake reviews running wild. I mean hell, consumers will buy a product knowing full well they might get a shoddy knock off and yet it's $5 less and they can get it tomorrow so they'll roll the dice. Sadly, we don't live in a world where people are intimately concerned with quality and accuracy in their purchases. edit: USBC not USB3

masklinn 4y ago
> Reviewers that try and apples to apples all products by comparing cost, size, advertised features and ergonomics are doing no better than you or I opening up a package and appraising it. Unless you're buying every product on the market and load testing them in your garage, some folks do a lot better than that (e.g. project farm, or torque test channel). But it clearly requires time and passion, and serious rigs for some of the tests (not everybody has a Skidmore lying around).

bsder 4y ago

What a useless article. How about some evidence and pointers to things that aren't? Humidity/pressure/temperature are actually the three measurements that probably aren't a scam. The sensor chips you can get are generally well-calibrated and do what they say. Do read the datasheet, though: there are lots of ways you can screw them up (soldering them wrong, for example). The CO2, VOC and particulate sensors seem to be absolute snake oil, though. I have yet to buy any device that "senses" these that has any correlation to anything resembling reality. Which seems kind of stupid because CO2 and particulate sensors shouldn't be that difficult. Volatile organics, though, tend to be difficult as they have a lot of confounding factors. I'd really love to have a recommendation for something that's been validated that isn't $10K+.

_yb2s 4y ago
I agree... I have a bunch of cheap indoor air quality measuring devices, and they all consistently read temp, pressure, and humidity close together. My CO2 meter measures exactly what I'd expect -high levels with windows closed, correct outdoor levels with windows open. My cheap PM2.5 air quality meter reads almost exactly what I see in purple air when I take it outside. Basically, I purchased a bunch of diverse cheap air quality sensor products that I have verified all read correctly, and are not scams. I don't think this article is accurate.
ThrowawayR2 4y ago
Why not look at bare HVAC sensors used for office building air quality monitoring? - https://new.siemens.com/global/en/products/buildings/hvac/sensors/air-quality.html https://new.siemens.com/global/en/products/buildings/hvac/se... - https://buildings.honeywell.com/us/en/brands/our-brands/bms/field-devices/iaq-sensors https://buildings.honeywell.com/us/en/brands/our-brands/bms/... Granted, they're not meant for standalone use but at least you're not wondering whether the vendor is reputable or whether the sensor does what it says it does. For example, at a casual glance, the Siemens QPA2002D VOC and CO2 sensor seems to be available for <$500 and comes with a fairly comprehensive datasheet.

f1shy 4y ago

I've an airthings (https://shop.airthings.com/GB_EN/view-pollution.html https://shop.airthings.com/GB_EN/view-pollution.html) sensor, which measures a bunch of things. The pressure is constantly less than 1000 hPa (after 1 year of having the device, not once was higher (I live at 100 m msl) so it must be higher. When I reported the problem, the technical support said "we use Bosch Sensors, so it is impossible that they are wrong". Not only the service is trash, but also the whole interface, which requires permanent internet connection. You can access from your phone the status of the air at your home from anywhere in the world... my fear is if anybody else also can. Notably, after 1 year, there was no SW update... I really doubt the device is safe. I only have it because of Radon measurements. And I hope they are at least more or less ok.

queuebert 4y ago
I've compared my Airthings to a mail-in radon test kit, and they were consistent, for whatever that's worth.

s0rce 4y ago

The south coast AQMD has a great website testing various air quality (mostly pm2.5) in lab and real-world situations against equipment http://www.aqmd.gov/aq-spec http://www.aqmd.gov/aq-spec

runjake 4y ago

PurpleAir sensors are pretty good, according to the scientists I’ve talked to (n=3). The outdoor models work inside or out.

S201 4y ago
They do! Although they require a correction factor to better match the government's fancy air quality monitors when measuring smoke. The EPA published a paper on it: https://github.com/shanet/ClearAir/blob/master/docs/PurpleAir%20PM2.5%20Correction%20and%20Performance%20During%20Smoke%20Events.pdf https://github.com/shanet/ClearAir/blob/master/docs/PurpleAi... While we're on the topic: Shamless plug for a PurpleAir clone I made last year that uses the same sensors but at half the cost (and keeps all of the data within your LAN): https://github.com/shanet/ClearAir https://github.com/shanet/ClearAir and https://www.digikey.com/en/products/detail/adafruit-industries-llc/4632/12715744 https://www.digikey.com/en/products/detail/adafruit-industri...
- runjake 4y ago
  So fantastic, thanks for the reply!

everyone 4y ago

I have seen some comments about air quality and particle counts here that I simply did not understand.. I live in a remote spot in the country in Ireland. I am surrounded by dairy farms (fields of grass with cows) I always have my windows open, all day all year round, though my room is super messy. People who know about this stuff, do you reckon I have good air quality?

megous 4y ago
Depends on how you/your neighbors produce heat if they are anywhere near. Villages' air can be pretty disgusting especially in colder months. Paradoxically, small cities when heated by remote heat can be quite enjoyable air quality wise all year round if you don't live near the main road.

yread 4y ago

I wonder when will personal CO2 scrubbers become a norm. With atmospheric CO2 growing ever higher and everyone having a CO2 detector (and an air "purifier") at home it's the next step.

genewitch 4y ago
you mean... plants? plants scrub CO2.
- kolinko 4y ago
  Plants scrubbing co2 indoors are pure placebo. You would need to convert half of your apartament with a tropical jungle to offset what you breathe out. They look pretty, though.
gsich 4y ago
Probably never. 1000ppm seems to be a value where the concentration has some negative effects.

2OEH8eoCRo0 4y ago

I agree with you but for most things it honestly doesn't matter. The time you wasted researching is worth more than whatever difference there might be. I also think we don't need any of this junk in the first place. Indoor air quality? Open a window. airnow.gov

mdp2021 4y ago
Economics is based on trade-offs, and a trade-off of "opening windows" can be "lowering indoor temperature". Incidentally: some parts of the world are in an energy crisis. Edit: also, that «whatever difference» clashes pretty heavily with > It is hilariously easy to inadvertently design a device that measures temperature with an error of 5degC, humidity error of 50% and pressure error of equivalent to 1km in altitude It is also difficult to avoid noting that we "look into things" for many reasons and also indirect gains; that there exist "silent killers" and, more importantly to some, silent harmers; that some "principle of inquiry" (of "knowing the world", of testing, like Galileo's "Saggiatore") and a "principle of wanting to get things done properly" are there...

ahaucnx 4y ago

Great article and I mostly agree. We launched our indoor air quality monitor AirGradient ONE at the beginning of this year. We measure PM, CO2, TVOCs, temperature and humidity. When we started the development we would have never thought that achieving an accurate temperature measurement was by far the most difficult thing. It took us 8 hardware iterations to get it right! We experienced with different enclsoure shapes, orientations and PCBs (component placement). Our experience is similar to the author of this article: Your biggest enemy is internal heat produced by active components, mainly the MCU but also by other sensors like the PM sensor and CO2 (NDIR). How we solved it: 1) Minimize heat from energy by using components that have low energy consumption and make extensive use of sleep functions of the MCU as well as sensor components (e.g. PM sensors can be put to sleep). 2) Make use of physics. Our monitor is wall mounted and uses the convection mechanism. So nearly all components that heat up like LEDs, MCU etc. are located at the very top inside the enclosure. Optimize the vents at the top and bottom of the enclosure and create an unobstructed air flow through the enclosure based on natural convection. 3) Plan for enough space. To get temperature right, you need a lot of air around the temperature sensor that is free from radiation from other heat sources. So we specifically designed the PCB to have the temperature sensor at a 'finger' at the bottom with a lot of space to other components and ensured there is a good air flow around. If you are interested to see our design, have a look at our open-source, open-hardware DIY Pro monitor [1]. We integrated a lot of the things we learned designing the commercial monitor mentioned above into these build instructions [2] that allow you to build your own highly accurate monitor and then also be able to change the firmware and adjust to your needs. In fact, our kit contains exactly the same plastic injected enclosure we use for our commercial monitor (but you can also just 3D print the one from the build instructions and get the other parts by yourself). [1] https://www.airgradient.com/open-airgradient/kits/ https://www.airgradient.com/open-airgradient/kits/ [2] https://www.airgradient.com/open-airgradient/instructions/diy-pro/ https://www.airgradient.com/open-airgradient/instructions/di...

matheweis 4y ago
What about outdoor pm2.5? I live in an area prone to frequent fog for many months out of the year. I learned that the fog will thoroughly disrupt the accuracy of pm2.5 sensors. After some research I found that running the air through a heated pitot or similar before taking a measurement will almost entirely correct this for somewhat obvious reasons; the fog is evaporated. As far as I can tell, none of the mid to high range weather stations have such a system and they will all be corrupted by a sight fog. I’ve resigned myself to making one… Does such a sensor even exist?

Maursault 4y ago

I bought a couple of expensive remote weather sensors because they were the only ones I could find that included sensing atmospheric pressure and wet bulb temperature along with the ordinary metrics like temperature and humidity. Though air quality and particulate count is not included, I have done without for two reasons, which is that I live in the country surrounded by water and forest and cleaner air than I have ever known, and in contrast, the small house is old, dusty, I can easily see the particulates floating in the air, and because I know it is bad, I just don't need to know any precise measurements. My only complaint concerning the devices, which seem to be rugged and accurate, though with an almost absurd accompanying price tag, is that the required app and its interface design is comically bad in every measure that could matter. If there are interested developers, please take a look at the product[1] and the software[2], and see if you're interested in developing and selling me and other customers, and perhaps even the manufacturer, an application that collects and displays data from this family of devices that doesn't completely and utterly suck. [1] https://kestrelmeters.com/products/kestrel-fire-weather-drop https://kestrelmeters.com/products/kestrel-fire-weather-drop [2] https://apps.apple.com/us/app/kestrel-link/id1489485544 https://apps.apple.com/us/app/kestrel-link/id1489485544

z9znz 4y ago
Indoor air quality can be greatly affected by all kinds of things in your home, from the building materials to the paints, coverings, veneers, veneer glues, fabrics, etc. etc. etc. So in other words, while your outside air may be quite good such that it doesn't negatively affect your indoor air quality, that does not at all suggest that your indoor air quality will be good.
- Maursault 4y ago
  I know, and I know it's bad in there, but knowing precisely how bad is not useful information. A week away and there's a film of dust on everything. Most places, the dust is human skin, but not here. I think it's the old veneer covering the cinderblock walls and the cinderblock. Place was built in the 1940's, and it is slowly deteriorating particle by particle. But the rent is cheap. I have a HEPA filter on a box fan for the bedroom that runs constantly, which I hope helps, and I spend my days outside.

dawnerd 4y ago

I bought an aranet4 which is excellent for co2 but it doesn't do pm or vo2. I can however infer that if the co2 is high I need to ventilate anyways. Crazy to see how high co2 rises on flights that are supposedly "refreshing air" often.

londons_explore 4y ago

I bought ~5 brands of air temperature sensor, and was surprised to find that when I left them in a sealed box overnight, every single one showed the same temperature to 0.1C. I was expecting them to have at least 10x that error!

ahaucnx 4y ago
The sensor modules are often not the problem. It is the heat radiation from other components in the enclosure that influence the temperature.
askvictor 4y ago
It's really easy to calibrate a temperature sensor.

EVa5I7bHFq9mnYK 4y ago

I see "wi fi connected" seems like a default choice now, not even questioning. I had one such CO2 detector, but then I realized that anyone gaining access to it (any employee of the manufacturer, for example) can know exactly when we are at home, when we are not, when we go to bed, when we go on vacation etc. So I disconnected it, bought a $70 device that measures everything pretty accurately and am happy ever since.

therealdrag0 4y ago
Which 70$ device? I also have one in that range and I don’t trust it.
- EVa5I7bHFq9mnYK 4y ago
  It's called Dienmern model DM72B, from Aliexpress, I compared its temperature, humidity and CO2 measurements with other devices and found them correct; as for PM2.5, HCHO and TVOC, I didn't calibrate, but they seem reasonable and detect smoke/farts immediately.
walterbell 4y ago
Would appreciate recommendation on non-WiFi sensor.
- EVa5I7bHFq9mnYK 4y ago
  Dienmern model DM72B, from Aliexpress

outworlder 4y ago

I wonder if a DIY version would fare better on their testing? Something like: https://www.airgradient.com/open-airgradient/instructions/diy/ https://www.airgradient.com/open-airgradient/instructions/di... I have bought all the parts, haven't had the time to assemble it yet.

ahaucnx 4y ago
Our old basic kit that you link above has also temperature inaccuracies due to its small footprint but we have a new kit that addresses these issues and is also available as a pre-soldered version for easy assembly: https://www.airgradient.com/open-airgradient/instructions/diy-pro/ https://www.airgradient.com/open-airgradient/instructions/di...

deleted 4y ago

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LorenPechtel 4y ago

It's not just air quality sensors. Got some wifi thermostats some years back. Oops--they draw too much power. At least it's consistent, we set them two degrees above what we actually want and and they work fine. And we also have an example of the problem of air circulation. We have a wireless thermometer (a quick check if it's cool enough to open the windows) that's in a weather enclosure that admits a decent amount of air and sitting under a tree (keeping it out of the sun and away from big masses of concrete--it's simply impossible to properly place it in our yard) and it can be up to two degrees off because of lag.

Mountain_Skies 4y ago

I purchased a 'Yvelines' brand air quality monitor. The company appears to be one of those random word Chinese generic product companies. Some of the readings spike when I take the unit into the garage where we park the cars, keep the lawnmower, gas can, etc. Most go down if I take the unit outside. I don't know how accurate the numbers actually are but it certainly can distinguish between areas with different levels of pollutants.

xani_ 4y ago

> I once saw a sensor chip that claimed to measure both CO2 and TVOC (total volatile organic compounds). After finding some further documents on the part I discovered it was a total scam. It only actually measured one of those things, then it used this measurement to look up an expected value of the other in a table the manufacturer made based off “common indoor measurements”. I remember similar thing with some UVC sensors, they just returned expected UVC based on UVA level

dalanmiller 4y ago

I'm looking for a comprehensive air quality measurement gadget for different rooms in my home. What devices are people using that aren't a _complete_ sham?

mrspuratic 4y ago
I got an Aprotii "7-in-1" sensor from Amazon UK for about €120 ("currently unavailable"). I haven't seen the same device from other vendors, which is unusual for this type of device on Amazon. Claims to be NDIR, can't seem to open it without trashing the glued down screen cover, so I haven't. I'm no expert on this type of device, I just figured anything less that €50 was going to be pointless. Lots of ventilation holes on 5 sides, a screen you can read from 8m away. Agrees (within tolerance) of a nearby temp/humid sensor. CO2 and VOC are independent. CO2 alone goes up during the day if I don't crack a window, VOC varies with how hot and close beverages are. PMs/VOC are mostly a function of how badly my cooking went in the adjacent kitchen :) I can't be certain about absolute accuracy of values, temp/humid are good, CO2 seems plausible: low is 400ppm, I start to get cranky while working by about 1200ppm. It's wifi (Tuya) if you want, the screen and controls alone are fine though. It also has RS485 and a bunch of relays to drive A/C, Fan, (de)humdifier too. There's a Spanish report that links Kkmoon/Kecheer/Curconsa/Aprotii device vendors: F. Villanueva, E. Jiménez, J. M. Felisi, T. Garrido, J. L. Jiménez, M. Ródenas, and A. Muñoz. Guide about affordable CO2 detectors for COVID-19 Prevention, versión 1.4, 17/04/2021. https://bit.ly/monitorsCO2 https://bit.ly/monitorsCO2 HTH.

QuantumGood 4y ago

Also home blood pressure monitors.

ck2 4y ago

So these are fake/inaccurate? That's a shame because I wanted to build one someday - but also they sell them to schools for CO2 monitoring? https://www.airgradient.com/open-airgradient/shop/ https://www.airgradient.com/open-airgradient/shop/ also previously on HN: https://news.ycombinator.com/item?id=28457135 https://news.ycombinator.com/item?id=28457135 > Monitoring my home's air quality (CO2, PM2.5, Temp/Humidity) with AirGradient's DIY sensor September 8, 2021 > A few months ago, I found this Hacker News post about the AirGradient DIY Air Quality Monitor. I had already been considering buying an AirThings Wave Plus sensor to monitor my home's CO2 levels, but the high price and limited 'ownership' of the data coming from it turned me off. also > AirGradient: DIY Air Quality Monitoring with Open-Source Hardware & Firmware https://news.ycombinator.com/item?id=27124671 https://news.ycombinator.com/item?id=27124671 https://www.airgradient.com/open-airgradient/instructions/diy/ https://www.airgradient.com/open-airgradient/instructions/di...

palisade 4y ago

I own an IQAir AirVisual Pro, it has identified when the air from ovens affect air quality. And, I bought a Honeywell HPA300 True HEPA Air Purifier and you can see air quality improve significantly when it is on. Also, when a large group of guests come over the CO2 monitor accurately tracks the large increase. And, it detected when Elon's factories had their fires. In addition, anytime there were forest fires in California it detected the increased pollution from those as well. The air quality several states away is affected by those fires severely btw, pretty interesting. The smoke plumes travel all the way to Maine. I've been pretty happy with both products. When the air quality drops outside, I close the doors and windows and let the air purifier do its magic. I leave the HPA300 on "Germ" mode, it is pretty quiet and still gets the job done.

Thaxll 4y ago

If you want high quality usb sensors: https://www.yoctopuce.com/EN/products/category/usb-environmental-sensors https://www.yoctopuce.com/EN/products/category/usb-environme...

neves 4y ago

IV bought one from Ali express that is a piece of garbage

mdp2021 4y ago

> most of my reviews would be worth dirt a month after publishing when either the items go out of stock or get their insides silently changed Very sad reality, from clothes to electronics. One wonders whether this run for cheaper builds while remaining relatively conservative in prices, unrestrained by a - missing - critical mass of discerning, demanding consumers, will end through some fading of the economic causes that triggered it. Or if this culturally polluting trend will stick now that it has been installed as a "normalcy".

mdp2021 4y ago
(Since I see that this is this quite alive: Update: real time: I have just been told in a shoestore, "No, forget about the good quality you could find years ago: it is either "meh" shoes or shoeless". I mean, I have good hope that if one made of finding good products a job in itself, with extensive effort, some reservoir may eventually be found, but really this whole situation is /very/ suboptimal.)

kimi 4y ago

AirSensEUR is an open framework focused on air quality monitoring using low cost sensors. The project started on 2014 from a group of passionate researchers and engineers. The framework is composed by a set of electronic boards, firmware, and several software applications. https://airsenseur.org/website/airsenseur-air-quality-monitoring-open-framework/ https://airsenseur.org/website/airsenseur-air-quality-monito...

Semaphor 4y ago

I don’t currently have air quality measurements, but I do have Aqara (not Wifi but Zigbee) temperature and humidity sensors. Zigbee uses less energy (afaik?) than WiFi or BT, and additionally, while there is no arrow, the symbol shows you which way is up, and it fits with the description (ventilation holes at the top). From what I’m reading, the fact that several sensors measure almost exactly the same values when mounted next to each other, is actually a good sign, correct?

kapep 4y ago
I have Aqara WSDCGQ11LM sensors which only have small holes for the sensor at the bottom but no ventilation holes for the main part of the board. At the bottom of the product page [1] they have an explosion graphic rendering which looks like (assuming it is somewhat correct) the sensor is below other chips and moved away from them. The sensor also seems to be shielded by having a separate area of it's own in the plastic enclosure. I haven't tested them yet but I think they should do fine, by the criteria of the article. - [1]: https://www.aqara.com/us/temperature_humidity_sensor.html https://www.aqara.com/us/temperature_humidity_sensor.html

specialist 4y ago

Teardowns as the new product reviews. Consumer Reports meets iFixit meets Twitch hybrid would be awesome. Plus the objective repeatability of Jepsen and TechEmpower. Some magical combination of authenticity, expertise, tenacity and personal narrative. As a noob DIY remodeler, I learned SO MUCH from channels like Project Farm, Matt Risling's The Build Show, Vancouver Carpenter, and others. For whatever reason, I didn't get nearly as much from content tailored to prior mediums, like This Old House and misc handy person magazines. (Probably some McLuhanian "medium is the message" insight applies...)

sizzle 4y ago

I have a senseair s8(?) that uses ladder to measure CO2 Can anybody tell me how reliable and accurate this sensor is?