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Air quality monitors: paying more does not get you more accuracy
- mdp2021 3y agoSlightly parallel: does anybody know if there exist products to detect more "local" pollution? Like an electronic nose that would be able to detect "sources", e.g. of mould or chemicals (for disinfection or fixing). I.e. not just the "room air quality", but spots causing it. (It is for a bit of an urgency that emerged in a building.)
- dementik 3y agoAfaik there are no simple sensors for this but havong gone through probably similar situation here, few things what I have learned: - voc sensor can detect lots of stuff, but reports just total value, still, voc sensor can be good way to detect if there is something wrong - our local laboratories have test sets which can be ordered home. Those cost something like 200eur, are placed e.g. on the table for an hour and those collect air. Then the unit is sent to laboratory which will report total voc (good to get a clue how right your own sensor is) and also detailed info on chemicals. For moulds there are different test sets - if some material is suspected to emit something, they can also identify material tvoc and detailed chemicals (so if there is some "bad" chemical on air sample, this is usually to confirm the source)
- deleted 3y ago[deleted]
- bullen 3y agoI bought the Pimoroni one and it broke after 6 months. Interesting to see the particles spike when frying food but other than that I only learned in which direction the wind has to blow for my air to be polluted (straight south so in the future might enable ionization then if pollution goes ballistic). What you need is a sensor that measures CO, CO2, all the hydrocarbons AND particles at different sizes. The Pimoroni could measure 1!, 2.5 and 10 PPM. Just use: https://maps.sensor.community https://maps.sensor.community and https://www.ventusky.com https://www.ventusky.com
- asdff 3y agoThat website isn't so useful outside of central europe for what its worth. Purple air is pretty good.
- varjag 3y agoLots of consumer things are basically layers of fancy molded plastic, marketing and some UI/convenience electronics above the same technology. For instance microphones.
- zX41ZdbW 3y agoGood instruction on building your own sensor here: https://sensor.community/en/sensors/airrohr/ https://sensor.community/en/sensors/airrohr/ As a bonus, the collected data by the sensors.community project is public, and here is the walkthrough of data analysis with ClickHouse: https://clickhouse.com/docs/en/getting-started/example-datasets/environmental-sensors https://clickhouse.com/docs/en/getting-started/example-datas...
- Avlin67 3y agojust open the windows the more you can
- noja 3y agoWell maybe not, but I was _very_ happy with Qing Ping Lite until its firmware update bricked it. I've never had an Eve device brick itself.
- fuzzehchat 3y agoThis is plainly not true at all. Cheap sensors aren't as good as expensive ones. This is like saying a DHT11 has the same accuracy as a SHT31.
- AlfeG 3y agoBut they don't compare sensor modules, they compare consumer devices
- thenickdude 3y agoHas anybody found an accessible solution for sensing PM0.1 (nanoparticles)? As far as I know the state of the art on these is condensation particle counters, which use a supersaturated gas (e.g. of isopropyl alcohol or butanol) to glom onto the tiny particles to make them big enough to be sensed optically. Are there any novel approaches, or maybe a cheaper CPC?
- Snuupy 3y agoCan you buy only the PCB of the AirGradient Pro (and not the entire kit)?
- ahaucnx 3y agoYes possibly. Please send us a message through our support form.
- mnw21cam 3y agoThe article is about PM2.5 consumer units, and I can well believe that price doesn't make much difference. However, I'd like to point out CO_2 - there are two kinds of sensor. One of them measures volatile organic compounds and assumes that CO_2 correlates with them, and the other actually measures CO_2. The second type costs around £40 for the raw sensor - if your sensor is cheaper than that then it probably isn't actually measuring CO_2.
- ImaCake 3y agoIf it's measuring VOCs and you live in a city then chances are it would be measuring car exhaust!
- michaelcampbell 3y agoIs that bad? I mean, VOC's are VOC's regardless of source, no?
- ImaCake 3y agoDepends if you care about CO2 and presumably the CO2 from breathing humans. The VOCs from cars in a busy city will mask/overwhelm/confound any measure of human body produced CO2 in that location. But a more suburban or rural location will be fine.
- pawelduda 3y agoFor CO2 I'm satisfied with airthings sensor. Hard to say how accurate the readings are because I didn't compare it to anything, it self-calibrated for a week first. From random tests I can see it reacts properly in indoor/outdoor/open window/few people sitting in unventilated room/someone exercising/cooking scenarios. Integrates with HomeAssistant through their cloud and seems like it's being pooled for readings so it's not perfect but not why I bought it. The main takeaway is that it takes more than I thought to keep indoor CO2 at bay, especially during winter when you have to deal with low temp/air pollution outside.
- flanbiscuit 3y agoA relevant discussion about air quality sensors from less than a year ago: "Many indoor air quality sensor products are a scam" - https://news.ycombinator.com/item?id=33025995 https://news.ycombinator.com/item?id=33025995 I almost bought Airgradient's pre-soldered kit[1] but I went with the Airthings View Plus[2] because it came with a Radon sensor. It's pricey (US$299), but not $1000 pricey as mentioned in the article. But I think I might still get the Airgradient sensor for another room just because it's cheaper and I don't need more than one Radon sensor. 1. https://www.airgradient.com/open-airgradient/shop/#!/DIY-Pro-Kit-Pre-Soldered-version-4-2/p/476627519/category=0 https://www.airgradient.com/open-airgradient/shop/#!/DIY-Pro... 2. https://www.airthings.com/en/view-plus https://www.airthings.com/en/view-plus
- alexk307 3y agoI wired up an SDS011 to an ESP8266 running esphome, and then integrated that to home assistant. All in all under $40 USD, and I’ve found it very sensitive and reliable
- kingsloi 3y agoInteresting article - good to know, too! I've been tracking air quality in Gary, IN for a few years now. It started with a PurpleAir ($), then a AQMesh pod ($$$$$) for a few months, now I'm rocking a Sensit RAMP ($$$). Just haven't spent too much time updating the dashboard I built to showcase the data: https://millerbeach.community https://millerbeach.community. I had one sensor up and running at a time, so couldn't compare all 3 (PM only) against each other. Indoors, I've been using a Canairi Air Quality Sensor, but that's just a simple CO2 monitor, along with my Dyson hot/cool air purifier. I'm looking for a rough idea of what my family are breathing, I don't mind if numbers aren't 100% accurate (hopefully as small -/+ %, though).
- chaxor 3y agoThis is probably a stupid question regarding the equipment, but it seems to be a good addition for the user, even if additional hardware underneath is required - why is CO not more common on these devices? Additionally, where are all the ppbv CO detection capabilities? (most are ppm, likely to not be a scare to humans but always reading "0", but it makes determining sensitivity or any response at all pretty difficult)
- StrictDabbler 3y agoCO detectors are life-safety equipment. The regulatory burden for laboratory certification and approval is much higher for them. If you put an air-quality detector into your device and it's reading 30% lower than reality it's no big deal. If you put a CO detector into your device and it's reading 30% lower than reality you may face massive liabilities. It isn't a "hey, why not" feature.
- FloatArtifact 3y agoWhy do you no longer sell the Pro PCB/ enclosure kit? In fact selling Pro PCB would make the project much more accessible.
- GuB-42 3y agoDon't go too low either. There are CO2 sensors on AliExpress for less than $10, they are scams. What they do is that they take the cheapest sensor available that reacts to something in the air, and extrapolate a reading. It may give you an indication that the air is "stuffy", but the numbers are completely made up.
- ahaucnx 3y agoAuthor here. I wrote this article a few weeks ago after discovering that a well known air quality monitor in the market that retails for more than USD 1000 actually uses a PM module that costs less than USD 20. Often people assume that the more expensive, the better but as you can see in the article this is often not the case -especially when it comes to the accuracy of the monitor. If you are looking for an open source / open hardware air quality monitor kit that uses high quality sensor modules and is very easy to assemble, have a look at the project we maintain. Instructions to built an indoor monitor [1], instructions to built an outdoor monitor [2] and overview of the kits [3]. All is open source (firmware, schematics, 3d files for enclosure, etc). [1] https://www.airgradient.com/open-airgradient/instructions/diy-pro-v42/ https://www.airgradient.com/open-airgradient/instructions/di... [2] https://www.airgradient.com/open-airgradient/instructions/diy-open-air-presoldered-v11/ https://www.airgradient.com/open-airgradient/instructions/di... [3] https://www.airgradient.com/open-airgradient/kits/ https://www.airgradient.com/open-airgradient/kits/
- reassembled 3y agoHave you compared the Sensirion SEN55 against the Plantower sensors? I ask because I’ve recently picked up both and have played around with them each individually but haven’t compared them for accuracy yet. The nice thing about the SEN55 is that it contains all of the sensors in one unit (PM1.0 to PM10.0, temperature, Relative Humidity, NOX and VOC). They do cost a little bit more than the Plantower units, about $30-40USD. For anyone looking at the Sensirion sensors, be aware that the SEN5x products span a range, and only the SEN55 has all of the above sensors in one unit. I’ve found the Sensirion software to be pretty nice to work with. I was able to port their embedded i2c example repo to ESP32 with little trouble.
- ahaucnx 3y agoYes, we are looking at the SEN55. The reason we currently still use the Plantowers is that there is a lot more research out there on the Plantower and how it behaves in different environments.
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- toomuchtodo 3y agoDoes anyone have experience with the open air monitor version [1]? I am looking for an affordable outdoor air sensor that will be used to collect data from certain urban and suburban areas to use as evidence in efforts to dissuade (through public comment periods and possible litigation) industrial rezoning near residential areas due to pm2.5 and other combustion emission pollution (and deploying a sensor network to establish a baseline). [1] https://www.airgradient.com/open-airgradient/kits/ https://www.airgradient.com/open-airgradient/kits/
- ahaucnx 3y agoThank you for mentioning our kits. The Open Air outdoor monitor has been designed in co-operation with scientists and is currently undergoing co-location testing on four continents to collect a large dataset and being able to completely understand the performance in different environments and to develop accurate compensation algorythms if required. The first results look very good. You can read more about it on our research page [1]. We get a lot of interest and support from the research community on this monitor as it is completely open hardware / open source. [1] https://www.airgradient.com/research/ https://www.airgradient.com/research/
- toomuchtodo 3y agoThank you for taking the time to reply! Genuinely appreciate it.
- baby-yoda 3y agoDoes AirGradient have any options that are connected and powered via PoE? The Awair Omni looks like a great option for what I imagine I'd like to set up but it would be nice to support Air Gradient if possible.
- veemjeem 3y agoThe AirGradient uses the D1 wemos as the microcontroller & network connectivity. There are D1 ethernet shields that have PoE that would make it pretty easy to slap on top of the d1 and provide this exact feature, however you might need to tweak the code a bit to switch the network access from wifi to ethernet.
- ahaucnx 3y agoWe currently don't have PoE but since it's open hardware and firmware people can look into adding it themselves. All documentation is open source.
- Rebelgecko 3y agoOne thing that's cool is that Airgradient's designs are super modular. I am on a crusade against micro-USB, so when I made an Airgradient Basic board I just used an ESP board with USB-C instead. If you can get a board with PoE with a similar form factor you might be able to just plop it on. Otherwise you can tweak the PCB and STLs to make it work.
- ahaucnx 3y agoFully agree. All our PRO kits have USB C and we also now use the D1 mini with USB C plug.
- synack 3y agoThere's some good empirical data about the cheap PM2.5 sensors that Adafruit sells on their forum. The sensor itself has a microcontroller that filters the raw values and you need to keep this in mind when interpreting the data. https://forums.adafruit.com/viewtopic.php?f=48&t=136528&p=767725#p767725 https://forums.adafruit.com/viewtopic.php?f=48&t=136528&p=76...
- athollywood 3y agoI bought a fairly expensive air quality monitor. Accuracy wasn’t what caused me to go with a more expensive model. I wanted CO2 readings, which most models under $200 don’t provide.
- bombcar 3y agoI suspect I know exactly which one you bought ;) I wish I could find a good source for "outside CO2 levels" as I think they've been elevated but I have no way to prove it (beyond my indoor sensor showing high).
- newman314 3y agoAranet4 is the way to go. Tried going cheap and getting a bunch of Vitalights later as additional monitors but ended up finding out that their results were all over the place. Returned the Vitalight. Kept the Aranet4. I do have plans to build a few Airgradients when I have time.
- tuatoru 3y agoCalibrating PM2.5 sensors looks difficult. Relative humidity, temperature, different mixes of inorganic and organic aerosols, probably air pressure, integration times -- lots of dimensions. PALMA[1] has a lot of work. 1. https://www.mdpi.com/2076-3417/11/19/9014 https://www.mdpi.com/2076-3417/11/19/9014
- spoonjim 3y agoThey probably all use the same Taiwanese component
- amatecha 3y agoMy three AirGradient DIY units are going strong. They seem very accurate -- strongly correlating with nearby weather stations and online services. Definitely nice to have high-granularity/accuracy details both indoors and outdoors. It's also really interesting to see different "trends" and how different weather conditions correlate with (and/or affect) air quality!
- 2rsf 3y agoAre there online co2 measurements from weather stations? I couldn't find any for Sweden
- amatecha 3y agoOh, not that I know of. I was more comparing against nearby stations in terms of temperature. Yeah, I couldn't find any CO2 either. I just check on aprs.fi to see nearby stations reporting their data via the APRS-IS network :)
- Johnny555 3y agoI was glad to see that the PurpleAir PA-II sensor (which I have outside and refer to often during wildfire season) has relatively good performance, at least for PM1.0 and PM2.5. PM1.0 R2 > 0.96, PM2.5 R2 > 0.93 https://www.aqmd.gov/docs/default-source/aq-spec/summary/purpleair-pa-ii---summary-report.pdf?sfvrsn=16 https://www.aqmd.gov/docs/default-source/aq-spec/summary/pur...
- sacnoradhq 3y agoPMS9003M is $15 shipped, add another $6 for an Arduino and a display. You can bet the $1000 ones are Better Technology Through Beautiful Marketing and Design(tm). Anyone who pays that deserves to be separated from their money.
- ARandomerDude 3y ago> Anyone who pays that deserves to be separated from their money. This a sad statement and simply untrue. The vast majority of people are in other fields, don’t know anything about hardware, and have never even heard the word “Arduino.” They don’t deserve to be scammed by con artists using fancy packaging as the hook.
- sacnoradhq 3y agoIgnorance isn't something to be defended, celebrated, or excused. Find hypothetical victims elsewhere because you're preaching against the ethos of this community.
- AceJohnny2 3y agoIt seems a lot of air quality monitors, such as the PurpleAir PA-II [1] , are just wrapping the Plantower PMS5003 [2], which is a turnkey particle sensor which integrates laser sensors, airflow, and MCU to perform measurements and spit out results on a serial bus. I'm pretty surprised by the lack of diversity in the "consumer" market. [1] https://www2.purpleair.com/products/purpleair-pa-ii?variant=40067691708513 https://www2.purpleair.com/products/purpleair-pa-ii?variant=... [2] available e.g. https://www.adafruit.com/product/3686 https://www.adafruit.com/product/3686
- samtho 3y agoI’ve used a lot of different sensors for random purposes and it’s almost always the same few companies (or a knockoff of them) at each the price point. Building a sensor-on-ic is more comparable to the process that pharmaceutical companies go through in their R&D rather than traditional logic chip makers. It’s a lot of experimenting, use of non-standard materials, and pushing fabrication techniques to their limits. They don’t have to disclose how it’s made in the same way as pharmaceutical companies are required to, however, which means they have a monopoly on the tech until someone decaps the IC and reverse engineers it.
- ruph123 3y agoI would not recommend the Airgradient diy kit to anyone. Have been using one for a while but the CO2 sensor is really unreliable and often spits out wrong values. VERY OFTEN. Last time this issue was wildly discussed by people using it e.g. in the link below which is using Prometheus but also in the forums of airgradient. All with no solution. https://github.com/geerlingguy/airgradient-prometheus/issues/24 https://github.com/geerlingguy/airgradient-prometheus/issues...
- ahaucnx 3y agoThis was an issue we had in one of the previous versions of the kit. Since then we have improved the hardware (now at version 4.2) as well as fixed it in the firmware. If you still have issues, please contact me through the link on my profile.
- _zoltan_ 3y agothe above linked GitHub issue is still open.
- rgovostes 3y agoThe above linked GitHub issue has been closed for over 6 months, and aside from that was posted to the wrong project rather than to an official AirGradient channel.
- ahaucnx 3y agoThis has been analysed extensively on our forum and the root cause was a bug in the software serial Arduino library as well as a slightly wrong command send from our library. Details [1] [1] https://forum.airgradient.com/t/co2-reading-of-3-constantly/605/6 https://forum.airgradient.com/t/co2-reading-of-3-constantly/...
- mtlmtlmtlmtl 3y agoArduino library eh? Would definitely recommend getting away from that as soon as possible. When I worked with avr controllers we eventually ended up writing all of our own library code because it was still faster than trying to debug these strange heisenbugs caused by gnarly bugs in the libraries. I specifically remember softserial was very problematic, and actually reading the code convinced me to dump it. Might be fixed now, but there's timing code in there that could easily break on a compiler update because it's still written in C++ and has handcounted delays based on counting instructions in compiler output. Now, maybe they recheck those on every single release of avr-gcc to make sure the count didn't change, but why rely on that? We're talking about the same maintainers here who kept conditionally compiled ASM code to manually push and pop the stack in every function because some absolutely ancient MacOS 9(or something like that) version of GCC somehow didn't emit those instructions. That was still there in 2015, hopefully they removed it since then... It also sets interrupts. I don't like library code doing this at all. I wanted complete control over that so I always know what interrupts might occur. And even worse it uses a circular buffer for storing data but IIRC offers no method of detecting a full buffer. Which led to a lot of "fun" debugging. Arduino libraries are fine for simple prototyping, but they're not high quality enough for writing reliable microcontroller code.
- pachico 3y agoThis is not a joke, I am really asking: how do you measure the accuracy of an air quality monitor? Comparing it to another monitor? Creating an air pollution condition and seeing how close to that is the measurement?
- crazygringo 3y agoYou don't really need super accuracy in the way you do for a body weight scale where a 2% change matters. You watch the readings go up and down as you close windows and cook and then open windows and let the fresh air in. You'll watch CO2 go up to 1200 and then back down to 500. Or PM2.5 go from 2 to 25 and back. They're big changes that obviously correlate in logical ways with what is happening in your home. And then it's really the relative changes you're watching. Even if values are off by 20% it doesn't really matter a ton for private personal use. Because you're really just learning what the baseline values are for fresh air, how quickly values grow, and therefore when you prefer to open some windows. (Or this week, close them.)
- baq 3y agoGeneralized, this is unsurprisingly a field of science: https://en.m.wikipedia.org/wiki/Metrology https://en.m.wikipedia.org/wiki/Metrology
- Rebelgecko 3y agoThe state of the art for reasonably priced CO2 monitors seems to be that they hard code in the "ambient" Co2 level and instructions tell you to let it sit outside every once in a while. The the sensor adjusts can adjust it's baseline accordingly , assuming that the lowest CO2 level it's seen in the last week or so is equivalent to the "ambient" outside level. Ofc this is susceptible to issues and can require even more adjustments since CO2 levels go up every year. A sensor from 10 years ago might read 5% lower than a modern one because it's using an out of date baseline CO2.
- adhesive_wombat 3y agoNew shareholder value opportunity: Pay an extra 10% and get a dynamic baseline model that hardcodes a baseline level and expected gradient of 0.5% per year. By the time the device lands in landfill, it probably won't ever have been too far off. And if the CO2 curve derivative starts to underperform and risk your deployed calibrations, throw some dollars an some anti-nuclear campaigns as that's cheaper than doing an update!
- idontwantthis 3y agoReminds me of dash cams which almost all use the same image sensor even if they advertise different levels of image quality.
- 2rsf 3y agoThat's actually a good example- in addition to the sensor a camera needs a lens, a body to hold everything together aligned and steady, power supply and some logic to control the device.
- Khaine 3y agoSo how does the Awair air monitoring compare?
- vbezhenar 3y agoI recently bought one air quality monitor (levenghuk wezzer something). Generally it works, but after few dozens of minutes its temperature sensor starts to display like +5 degrees compared to proper temperature. Very weird.
- Leo_Germond 3y agoMembrane sensors have to get very high in temp locally in order to do a membrane cleanup, thos being large compared to a temp probe, the probe is probably catching of the heat because it is not properly isolated. Some SW model for heat flux can somewhat reduce this effect but in general this is AFAIK an open problem for miniaturized AQ sensors.
- Wolfenstein98k 3y agoI think it's because the unit heats up over time, and its sensor can't adequately adjust for that. My baby monitor does the same thing - the temperature tracks up after a half hour or so. The unit is warm to the touch by that point.
- cinntaile 3y agoHas anyone opened up their https://www.birdie.design/ https://www.birdie.design/ and checked what sensor they use? They don't disclose it.
- supermatt 3y agoNot sure, but its just CO2 - not PM.
- nabla9 3y agoIf you want more accuracy, buy 2-3 different cheap air quality monitors and average.
- ioulian 3y agoFor people who use Home Assistant, I've gone with DIY route with ESPHome [1] and senseair CO2 sensor. You can buy those sensors for +- 26 USD on AliExpress. Together with 5 USD, ESP32 devkit, it's mostly "solder"-n-play. Of course, I only have one of them, so I can't say if they are accurate, but I just need to know if the CO2 levels are normal (+- 400ppm) or high (+1000ppm), to open a window. I have tested it with just blowing on it, the CO2 value jumps up, putting it near a window, goes directly to +- 400. I haven't had any strange readings with it, ESPHome developers really made an excellent product, that is stable and "just works". You can even calibrate the sensor by putting the it outside (but I haven't really bothered with it). ESPHome has also support for a lot of other sensors that you combine on a single ESP32 module. [1] https://esphome.io/components/sensor/senseair.html https://esphome.io/components/sensor/senseair.html
- plett 3y agoI attached a cheap IKEA Vindriktning PM2.5 sensor to esphome to get air cleanliness data into Home Assistant [1]. That's also very simple to do - solder some wires and write a few lines of yaml and it shows up in the web UI. I bought two of them and they are accurate to each other, so the sensors appear to be acceptable. [1] https://plett.uk/posts/ikea-air-sensor/ https://plett.uk/posts/ikea-air-sensor/
- jve 3y agoThey are extremely inaccurate. But relative measurement is OK - you can see rising or falling pollution. When I put one in kitchen it "died" pretty fast - I think the cooking oil grease got onto the sensor and it is game over for me. Shows MAX PM2.5 all the time.
- noja 3y agoDo you know if the new ikea air quality sensor has the same fan as the first one? The original had a fan that would turn on and off every ten seconds.
- joecool1029 3y ago
- Havoc 3y agoTo a point. Eg I bought both a bme680 and scd41. Ie one co2 equivalent and one real one. The difference is sizable. Equivalent is basically garbage data. Correlates a bit with say opening a window but that’s about it Esp in absolute values. The trend seems vaguely ok