[HN Gopher] Many indoor air quality sensor products are a scam
___________________________________________________________________
Many indoor air quality sensor products are a scam
Author : clairity
Score : 180 points
Date : 2022-09-29 19:40 UTC (3 hours ago)
(HTM) web link (halestrom.net)
(TXT) w3m dump (halestrom.net)
| EVa5I7bHFq9mnYK wrote:
| 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.
| ahaucnx wrote:
| 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/ [2]
| https://www.airgradient.com/open-airgradient/instructions/di...
| ahaucnx wrote:
| An interesting story:
|
| In our journey to get the temperature right, we made extensive
| use of thermal imaging and compared our prototypes with
| competitors.
|
| The images showed that one of these sensors got extremely hot
| during operation but the temperature was nearly identical to
| the real ambient temperature. We couldn't believe this.
|
| So we made a test and put a strong fan onto this sensor. The
| temperature then dropped by more than two degrees Celcius BELOW
| ambient which showed clearly that they made a software offset.
|
| It can be debated if such an offset is a legitimate design
| choice (and I personally believe it has a lot of risks) but it
| was something we wanted to avoid in our design.
| megous wrote:
| Looks like non-professionals have easier time with this. :) I
| did put DHT22 into a breadboard, some atmel mcu on the other
| side to convert from DHT's protocol to UART and half a meter of
| wires to UART of Orange Pi SBC which serves as a
| logger/controller. Open air design, lot of space, far away from
| anything that heats up air.
|
| Sensors hanging off wires may look ugly, but it has benefits.
| ahaucnx wrote:
| Yes I agree. Much easier. That was basically our version 0 ;)
| Maursault wrote:
| 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
|
| [2] https://apps.apple.com/us/app/kestrel-link/id1489485544
| z9znz wrote:
| 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.
| monopoliessuck wrote:
| 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
| ThrowawayR2 wrote:
| Even if such a service existed, it wouldn't accomplish much.
| OEMs are free to change the design and internals of their
| products at any time and many have had no choice but to do so
| because of semiconductor shortages.
| mistrial9 wrote:
| this is literally nonsense -- every electronic device in the
| USA sold to consumers must conform to basic standards, and
| stay that way. At face value, the reply says "you cannot
| really rate devices"
| monopoliessuck wrote:
| Oh, of course. You can compare external product numbers, but
| often these aren't updated when things change. That's not
| even getting into buying Levi 501's from Kmart will get you
| an inferior product compared to buying them from levi.com
| despite being marketed as the same product. Companies too
| will often abuse their brand and former good will in order to
| ship sub par products today that look almost like their
| products of yesteryear -- doubly so after an acquisition. I
| have a friend that is into Rubiks cubes and when asked which
| cube I should buy he just said.
|
| > Any of them are great, except if they come from Rubiks
|
| I still think being defeatist about this isn't helpful. More
| information, even if it's not complete and timeless is good.
| I think if this kind of information proliferated too,
| companies would have a disincentive to update what is loved,
| works and isn't broken.
|
| Also, I realize the chip shortage is a real issue and has had
| genuine effects... still companies will find any external
| boogie man for why their products should get weaker, their
| turn around times longer and their products' sticker prices
| higher.
|
| You can't forget the "but verify" part of "Trust but verify"
| psadri wrote:
| Unfortunately, there is no business model to support this.
| People don't want to pay to support unbiased product review
| sites. And as they say - "if you're not paying for the product,
| you are the product"
| bityard wrote:
| > while the majority that bought and got a number _loved it_
|
| This seems to be Amazon's main unspoken strategy behind
| promoting positive reviews... many people want to be helpful
| and provide a review of a product that they purchased. That's
| great, but the problem is that most people are thoroughly
| unqualified to review things: "I took it out of the box and
| turned it on, five stars!"
|
| (And I'm not even going to mention Vine Voice or whatever it is
| called, these are reviews you should ALWAYS ignore because they
| are given free products in exchange for ostensibly unbiased but
| implicitly biased reviews.)
| monopoliessuck wrote:
| Agreed, and that's if they review the product at all.
|
| Lots of reviewers talk about the delivery, how Amazon Prime
| bungled the return or even a completely different product;
| all completely unrelated to the actual features of the
| product you'll be buying. Pair that with how Amazon allows
| companies to put completely different products on the same
| offering with "variants" that are again abused by companies
| to transfer reviews from a well received product onto a
| poorly received one. Most users just look at the five start
| v. one star ratio in the end anyway so an electrician going
| over a wire gets the same final weight as someone that
| confusingly put a question in the review box.
|
| I've put up good quality critical reviews too and had them
| silently removed. Amazon may be an okay place for getting an
| item, but too many people use it as a discovery and curation
| vehicle and that's where the manipulation starts and ends. I
| get better product recommendations looking almost anywhere
| else than the Amazon search box.
| z9znz wrote:
| There are lots of "favorites", but one of my favorites is
| when someone rates it highly and says that they ordered it,
| haven't yet received it, but are very excited to try it. So
| in other words, they have no idea, but they are so hopeful
| and excited they already rated it!
| monopoliessuck wrote:
| My favorite is the question and answer area where they
| answer "I don't know".
| cbhl wrote:
| WireCutter (since bought by the NY Times) literally has an
| article on this subject.
|
| https://www.nytimes.com/wirecutter/reviews/best-home-air-qua...
|
| I bought one of their prior recommendations, the "Kaiterra
| Laser Egg+ Chemical", and as far as I could tell it did the
| "TVOC-to-CO2" lookup table conversion mentioned in this
| article, and so it would give CO2 readings that were
| inconsistent with same-branded CO2 sensor ("Kaiterra Laser Egg+
| CO2"). WireCutter seem to have since updated the recommendation
| to something with a different type of sensor.
| masklinn wrote:
| > 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).
| monopoliessuck wrote:
| There are some good reviewers out there yeah. Sadly, they
| often rely on the creator's passion moreso than getting paid
| by their audience to provide a service. Youtube ad revenue
| and Amazon affiliate links are keeping these people's lights
| on more than the "thank you's" of their most ardent
| "supporters".
|
| Google tightening the belt on Youtube monetization is
| probably, strangely, the best thing that could have happened
| to mostly-direct payments to content creators. Patreon and
| the like have made viewers at least somewhat more willing to
| pay out to access content. On the flip side, it seems to have
| also led to an explosion of more biased reviewers pushing
| their own discount codes and affiliate links to make up the
| difference.
|
| There's a cultural misalignment somewhere. Journalism still
| hasn't cracked the nut nor has scientific peer review.
| Information curation and verification isn't cheap regardless
| of how much we'd like it to be so.
| Fatnino wrote:
| It was usbc cables
| monopoliessuck wrote:
| Right, thanks. Fixed
| ahaucnx wrote:
| Since the 1960s we have "Stiftung Warentest" in Germany which
| does unbiased indepth product reviews and is a very popular
| magazine. They review more than 200 products every year and the
| tests are carried out by independent external test labs
| worldwide.
| aoki wrote:
| > For awhile this Google dev was putting up extremely detailed
| amazon reviews for USBC cables
|
| https://en.wikipedia.org/wiki/Benson_Leung
| skunkworker wrote:
| For tools and other items that you might get from Home Depot,
| Project Farm is pretty much the standard now in my book.
| https://www.youtube.com/c/projectfarm
| jzawodn wrote:
| Agreed. He's doing fantastic work.
| agumonkey wrote:
| I automatically upvote his vids now. I hope people get
| inspired by him.
| [deleted]
| outworlder wrote:
| I wonder if a DIY version would fare better on their testing?
|
| Something like: https://www.airgradient.com/open-
| airgradient/instructions/di...
|
| I have bought all the parts, haven't had the time to assemble it
| yet.
| ahaucnx wrote:
| 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/di...
| bsder wrote:
| 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+.
| UniverseHacker wrote:
| 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.
| runjake wrote:
| PurpleAir sensors are pretty good, according to the scientists
| I've talked to (n=3). The outdoor models work inside or out.
| S201 wrote:
| 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/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 and
| https://www.digikey.com/en/products/detail/adafruit-industri...
| runjake wrote:
| So fantastic, thanks for the reply!
| yread wrote:
| 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.
| f1shy wrote:
| I've an airthings (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 wrote:
| I've compared my Airthings to a mail-in radon test kit, and
| they were consistent, for whatever that's worth.
| s0rce wrote:
| 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
| everyone wrote:
| 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 wrote:
| 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.
| jeffreygoesto wrote:
| 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.
| slig wrote:
| I bought a couple of Figaro TGS2602 from Aliexpress and they
| were quite sensitive to "human gas emissions".
| myroon5 wrote:
| Why drop? Less gas afterwards?
| qqqwerty wrote:
| 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 wrote:
| It's a relative indicator, so it would spike and then
| (relative to that spike) drop steadily as the VOCs diffuse
| and vent.
| clairity wrote:
| 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 wrote:
| > 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 wrote:
| oh, right, dunno where that brain fart came from... thanks
| for the correction!
| kaybe wrote:
| Nice, I'd be interested in a write-up with plots!
| JTbane wrote:
| Could you use this to detect flatulence in adults?
| IvyMike wrote:
| DIY: https://projects.raspberrypi.org/en/projects/fart-
| detector
| dpwm wrote:
| If you were to have an array of such sensors, perhaps you'd
| be able to estimate direction of travel.
| checkyoursudo wrote:
| "I'm sorry, Frank. The sensors don't lie. I'm going to have
| to ask you to leave."
| fghorow wrote:
| Now _there_ is a budding seismologist 's answer! ;-)
| odysseus wrote:
| 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 wrote:
| My kids call our winix purifiers "fart detectors"
| wil421 wrote:
| 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 wrote:
| 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.
| SrslyJosh wrote:
| 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 wrote:
| 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.
| e63f67dd-065b wrote:
| 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 wrote:
| 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 wrote:
| 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.
| sbierwagen wrote:
| 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.
| autoexec wrote:
| This could be a cool project for a raspberry pi...
| sbierwagen wrote:
| The sensor I used: https://www.seeedstudio.com/Grove-
| CO2-Temperature-Humidity-S...
|
| Claims to be 3.3V compatible, (Rpi voltage) which I haven't
| verified, since I ran it off an Arduino. (Which is 5V)
|
| From the Seeed docs: "When activated for the first time a
| period of minimum 7 days is needed so that the algorithm
| can find its initial parameter set for ASC. The sensor has
| to be exposed to fresh air for at least 1 hour every day."
|
| Disregard that entirely. When I tried to use the built in
| autocalibrate, it would set the floor value to 390ppm at
| some random time of day, not even close to diurnal minimum.
| Not to mention outside air is more like 420ppm now. (The
| problem with burning a minimum CO2 number into ROM is that
| the number is always going up...) I just disabled
| autocalibrate, stuck it outside for an hour, and hardcoded
| an offset in user code.
|
| The Seeed carrier board puts an ornamental cover over the
| sensor to make it look prettier. You can remove it if you
| want to reduce self-heating.
|
| The SCD30 uses i2c address 0x61, so it should coexist on
| the same bus as the BME280 temperature sensor, (0x76) if
| you want more accurate room temp:
| https://www.seeedstudio.com/Grove-BME280-Environmental-
| Senso... (Seeed will _not_ warn about address
| incompatibilities during checkout if you buy two sensors
| with the same address. Ask me how I know.) If you enjoy
| random number generators, you can also pick up one of the
| bad hot-wire "air quality" sensors that GP dislikes.
| https://www.seeedstudio.com/Grove-Air-Quality-
| Sensor-v1-3-Ar...
|
| Disclosure, I used to work for a company that resold all
| this stuff, before it was bankrupted by the semiconductor
| crisis.
| s0rce wrote:
| I build one with the SCD41, seems comparable, was a bit
| cheaper.
| ThrowawayR2 wrote:
| Try buying the CO2 monitors intended for
| agricultural/greenhouse use from a agricultural specialty store
| that's within your country. They won't be as inexpensive as the
| consumer units but at least you'll have some confidence that
| the readings are accurate.
| kzrdude wrote:
| Could you calibrate vs outdoor atmosphere CO2 from a local
| weather station?
| s0rce wrote:
| 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 wrote:
| 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.
| site-packages1 wrote:
| 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.
| izacus wrote:
| I have these for a year and I'm rather happy with them. The
| view plus acts as a hub for the minis and the values measured
| correlate with smells and stale air feel of the rooms. They did
| help me significantly improve my sleep quality.
|
| The fact that they have a good API made them worth the fairly
| steep entry price.
| sliken wrote:
| 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.
| RL_Quine wrote:
| 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.
| RivieraKid wrote:
| 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.
| Syonyk wrote:
| > _I 'm just looking for an indoor air quality monitor for
| temperature, humidity, co2 and ideally pm2.5 and pressure._
|
| If you don't want it to be "connected," try a TemTop P1000.
| I've torn one apart, and I have it in my office right now - it
| seems to do what it says on the tin sanely. Temperature,
| humidity, PM2.5, PM10, and CO2 levels. I have another TemTop
| unit and they generally agree within some reasonable margin of
| error, and they do seem to independently measure things like
| VOC vs CO2 - I can see one rise without the other, depending on
| what I'm doing.
|
| It doesn't have pressure, though.
|
| https://www.sevarg.net/2021/08/28/temtop-air-quality-sensors...
| shadowpho wrote:
| >I'm just looking for an indoor air quality monitor for
| temperature, humidity, co2 and ideally pm2.5 and pressure.
|
| That's because it's $$$$. CO2 is hard to measure (it's inert!),
| and only recently advances in NDIR allow us to measure it
| directly. Those are still $50, and that's just component cost.
|
| PM2.5 is also around $50 for decent parts.
|
| Another $10 for T/H/P. Another $20 for cheapest LCD you can
| find.
|
| Ok, so we are up to $130, but now you gotta pay for
| manufacturing ($$$), PCB, hardware development, calibration,
| testing, mechanical design... Probably $200-$300 total
| depending on quantity.
|
| So, let's say you can make the whole device for $250 just in
| costs. Now you gotta add software (BT\Wifi code is not fun!),
| shipping, overhead, profits. So, you gotta sell this thing for
| $350+.
|
| Would you buy one for $350?
| robga wrote:
| 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/
| ahaucnx wrote:
| Thank you for mentioning us. Since a few months we have an
| improved AirGradient PRO kit [1] that has a much better design,
| temperature accuracy and enclosure. It is fully open-source,
| open-hardware including 3D enclosure files.
|
| [1] https://www.airgradient.com/open-airgradient/instructions/
| RL_Quine wrote:
| 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.
| toss1 wrote:
| >>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 wrote:
| For the outdoor version, the magic search phrase is "personal
| weather station".
| colechristensen wrote:
| Except for the sensor that straight up didn't measure something
| it was reporting, "scam" is a strong word for inaccuracies.
| dawnerd wrote:
| 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 wrote:
| 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 wrote:
| The sensor modules are often not the problem. It is the heat
| radiation from other components in the enclosure that influence
| the temperature.
| askvictor wrote:
| It's really easy to calibrate a temperature sensor.
| ars wrote:
| 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 wrote:
| 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.
| com2kid wrote:
| 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 wrote:
| 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.
| TylerE wrote:
| 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 wrote:
| 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 :( )
| 2OEH8eoCRo0 wrote:
| 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
| zokier wrote:
| scam implies malicious intent. being crappy is not a scam.
| IggleSniggle wrote:
| 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.
| kqr wrote:
| 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 wrote:
| The malice is in taking my money in exchange for a product the
| seller knows to be worthless.
| aidenn0 wrote:
| GP was implying the seller didn't know it was worthless.
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