[HN Gopher] Ikea Vindriktning Air Quality Sensor Review and Accu...
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       Ikea Vindriktning Air Quality Sensor Review and Accuracy
        
       Author : ahaucnx
       Score  : 376 points
       Date   : 2021-12-06 11:26 UTC (11 hours ago)
        
 (HTM) web link (www.airgradient.com)
 (TXT) w3m dump (www.airgradient.com)
        
       | DannyBee wrote:
       | I would be very careful with this kind of evaluation. There are
       | lots of sensors that perform well vs reference instruments but
       | not in the field.
       | 
       | If you want real evaluations, SCAQMD (the folks in charge of air
       | quality for southern california) do evaluations of commercially
       | available, low cost sensors, both against reference instruments
       | and the lab.
       | 
       | See http://www.aqmd.gov/aq-spec/evaluations
       | 
       | You can see what i said is true from the table - _lots_ of
       | sensors that are very well correlated with reference instruments
       | in the lab, but suck horribly in the field.
       | 
       | I would think you would be better off submitting the sensor in
       | question to them, and letting them put it through its paces.
       | 
       | (They publish within a month of finishing testing, and testing
       | takes ~8 weeks)
        
         | hedora wrote:
         | Thanks for the link; that's a great resource!
         | 
         | To summarize their current results: Purple Air (especially
         | version 2) is the only one that doesn't suck at measuring PM
         | 2.5. None of the consumer-targeted gaseous sensors they tested
         | work.
         | 
         | Did I miss something? Is some other third party running more
         | comprehensive tests?
        
           | DannyBee wrote:
           | Assuming you care PM1.0/PM2.5 (which are what are truly
           | harmful), and want R^2 >0.9:
           | 
           | Atmotube pro Elitech (for PM2.5) Purpleair
           | 
           | The field evaluations have good expositions of the underlying
           | data in slide form. For sure the purpleair is the best bet
           | that i can see. Note that they are pragmatic as well - if you
           | read field evaluations, AQMD folks generally think >0.8 R^2
           | is very good. Which probably makes sense comparing a $50-$250
           | device to a several thousand dollar reference instrument.
           | 
           | Note that one serious issue is that a bunch of the sensors
           | aren't just uncorrelated, they are often dramatically
           | undercounting. It would be one thing if they were
           | dramatically overcounting, and told you air was horrible when
           | it wasn't. But they are actually telling you air is fine when
           | it isn't even close to fine.
           | 
           | I actually went down the same path as OP about 6 months ago.
           | I have used a dylos meter in my old woodshop, and was
           | building a new one, and wanted to see what the the best thing
           | to do was. After a bunch of looking, i found these folks. I
           | am not aware of others doing this breadth of testing.
           | 
           | (It turn out the dylos meter is either accurate, or
           | overcounts, depending on temperature/humidity. This is
           | actually acceptable since it won't tell me things are good
           | when they are bad, but it also turned out the purpleair was
           | consistently good for the same price :P)
        
           | formerly_proven wrote:
           | So the two purpleair devices are using PM1003 and PM5003
           | sensors, respectively. These are available off the shelf as
           | well. I suppose the salient question is: does purpleair
           | calibrate / select these themselves or add anything to them
           | (e.g. filter), or can you just use a PMS5003 for 30 bucks and
           | get similar results?
        
             | genewitch wrote:
             | Afaik you can use the $30 module and be within acceptable
             | tolerances, but you really should have at least a
             | temperature and humidity sensor as well, because as that
             | changes the other sensors will report differently.
             | 
             | I've noticed that even being exposed to pure carbon dioxide
             | the sensors I have will increase the counts of CO, VOC, and
             | HCHO, which is unlikely and a false read.
             | 
             | I only care about CO2 for my devices, so my two $30 sensor
             | based devices are fine.
        
           | Gatsky wrote:
           | The Sensirion does pretty OK for the price and form factor.
        
         | jiveturkey wrote:
         | +1
         | 
         | I don't have a problem with the OP's analysis of the Ikea
         | sensor. It seems generally reasonable. But rather with their
         | implication that the DIY sensor being promoted is of higher
         | quality.
         | 
         | Because accuracy is very much a "finished product"
         | implementation issue, not just the sensor itself, such
         | implication is off-base, particularly in direct comparison to
         | any finished commercial product. The accuracy of the DIY
         | version is going to vary -- a lot -- depending on the builder
         | of such.
         | 
         | I wonder if AQMD would evaluate a "reference build" of the DIY
         | sensor, seeing as there is an enclosure as part of the
         | "reference" implementation. At bare minimum, the airgradient
         | site should have comparison to highly ranked (by AQMD) sensors,
         | such as purple air. I'm actually quite surprised there are no
         | such comparisons on the site.
        
         | dognotdog wrote:
         | IMO, the single biggest problem is that even five-figure
         | reference instruments disagree considerably in the 0-20 ug/m3
         | range, and if you look at the figures of the SCAQMD tests, you
         | won't see much more than noise in the scatter plots in that
         | range, with increasing consistency at larger concentrations.
         | Some of this is due to mismatches in response times and
         | synchronization, but a lot of it is due to different
         | disturbances, noise processes, and varying sensitivities to
         | different particle size distributions in different sensor
         | types.
         | 
         | With inexpensive optical scattering sensors, the situation is
         | even worse. While it is easy enough enough to "count"
         | individual 2.5um particles, the scattering equations work out
         | to an order of 10^6 reduction in scattering amplitude, per
         | particle, going down to 0.3um (when measured with red or infra-
         | red light), and different particle compositions will scatter
         | differently. On top of that, the number of particles increases
         | significantly per unit mass concentration, making the signal
         | processing a lot harder once one can't just threshold
         | individual "blips" in the signal.
         | 
         | Whether the sensors are particle counting or nephelometric in
         | principle, the basic trade-off is that to see smaller
         | particles, they need higher amplification factors, which in
         | turn increases thermal noise, also amplifies stray light, and
         | makes the device more sensitive to EM interference. Many signal
         | processing pipelines do simplistic noise filtering, throwing
         | out much of the baby with the bathwater.
         | 
         | On top of these principal difficulties, the optical scattering
         | type sensors are quite sensitive to temperature variation, and
         | aging of the photoelectronic components, which is why field
         | tests under varied conditions often depress their accuracy even
         | further.
         | 
         | Long story short, it is very easy to build a sensor with
         | qualitatively good correlations to actual PM concentration, as
         | long as the PM concentration is sufficiently high, but the
         | health effects have no threshold, and every added bit of
         | pollution counts, starting at zero. Unfortunately, commodity PM
         | sensors are quite bad at quantifying these low, yet meaningful,
         | ambient pollutant levels, which is probably why IKEA chose
         | their traffic light thresholds the way the did: not because of
         | how it relates to health, but because this is what they could
         | do with a $12 device.
        
       | jansan wrote:
       | My takeaway from the article: Buy the sensor, make sure air
       | quality is in the "good" range (green light) and you will be
       | fine. I think I will order a few.
        
         | tdrdt wrote:
         | Exactly. Recently I bought a very cheap CO2 meter. It is
         | inaccurate, but still accurate enough for 99% of the people.
        
           | TheBlerch wrote:
           | Which CO2 meter did you get, how accurate is it and how much
           | did it cost? Agreed people just need a meter good enough to
           | tell them when air quality isn't good.
        
             | tdrdt wrote:
             | The brand is Simr, but I think there are only 3 or 4 meters
             | that are sold as whitelabel and rebranded a thousand times.
             | I think it was around $30.
             | 
             | Outside it measures around 400ppm so the base point is
             | good. Inside it measures 480ppm with good ventilation. When
             | someone farts it goes to 2000ppm for a while. So I think it
             | measures 'alright'.
        
               | mh- wrote:
               | I'd pay $30 for a fart detector. CO2 accuracy would just
               | be a bonus
        
           | numpad0 wrote:
           | Referring to acetone detectors with lousy linear lookup
           | feature as "eCO2 sensor" is infuriating but do I must admit
           | it's an okay reminder for room occupants to open windows...
        
         | etimberg wrote:
         | Agreed. I think I will buy at least one given that the cost is
         | so low.
        
         | blackbear_ wrote:
         | > Conclusion: [...] However, the defined cut off values for the
         | air quality and its description as "Good", "OK", and "Not Good"
         | are not based on science or international recommendations and
         | create the false understanding that the air is good, when in
         | fact it is not good at all.
        
           | jansan wrote:
           | Considering that the article was basically written by somone
           | who is selling competing products I would take this statement
           | with a truckload of salt.
        
             | colechristensen wrote:
             | I'm not selling anything and unless the writer is outright
             | lying about the number ranges, I agree with them. The
             | "green" range is way too lenient and the sensor will only
             | help you keep away from really terrible air quality, most
             | people would have it green always while doing nothing at
             | all.
        
               | jansan wrote:
               | As I understand it "yellow" will indicate better air
               | quality than "Unhealthy for Sensitive Groups" according
               | to the US standard. I see a difference between "Unhealthy
               | for Sensitive Groups" and "really terrible air quality"
               | as you describe it.
        
       | micheljansen wrote:
       | The article already mentions connecting a Wemos D1 mini, which
       | lead me to searching for a howto. Stumbled onto this excellent
       | article by my old friend Guy, complete with assembly pictures:
       | https://style.oversubstance.net/2021/08/diy-use-an-ikea-vind...
        
       | simonebrunozzi wrote:
       | It's almost incredible that for something as "simple" as an air
       | quality sensor, particularly in relation to PM2.5 (the most
       | important metric for most buyers, IMHO), there's no simple answer
       | as: product X costs $50 and provides 99.X% accuracy; product Y
       | costs $200 and provides 99.9X% accuracy.
       | 
       | Two years ago, during one of the most intense fire seasons in
       | California, I spent a few hours studying different solutions, and
       | ended up buying a refurbished PurpleAir sensor. It seemed to work
       | great, but I felt it was a bit too expensive for what it was
       | doing, too bulky, and in general not as easy to use for the
       | ordinary person as it should be.
       | 
       | Same problem with home air filters - if you want to purify the
       | air in your house, there's too many snake-oil solutions out
       | there, and few that are worth the spending.
        
         | ortusdux wrote:
         | Finding myself in a similar situation with last years fires, I
         | have had great luck with the WINIX air filters sold at costco.
         | I bought 2 on sale for $100/ea. They are 5 staged with HEPA and
         | charcoal filters, have a built-in air quality monitor of
         | unknown quality (I should open one up one of these days), and
         | they have an ok app that allows you to check air quality and
         | adjust their settings. Each unit includes 2 years of filters,
         | and they look to be about $30/year/unit to replace after that.
        
         | hedora wrote:
         | Air filtration and monitoring are a classic market for lemons.
         | 
         | Wirecutter has decent-ish tests of air filters, though they
         | assume tiny New York apartments, so you have to dig around a
         | lot to find results for larger units.
         | 
         | (From reading their review, you'd think >1000 sq ft homes are
         | unheard of in the US, but the average is closer to 2000 sq ft)
        
         | s0rce wrote:
         | If you have some electronics experience you can buy the
         | Plantower sensors that PurpleAir uses and connect it to a
         | microcontroller, there are guides mentioned in the comments
         | here.
        
       | baxuz wrote:
       | Oh, I was just about to buy a few.
        
         | [deleted]
        
       | rceDia wrote:
       | Cheap, easy to use is o.k. not sure of reliability. Another IOT
       | at home air quality solution is Purple Air. Offers units for
       | outdoor or indoor. Not as cheap as IKEA but affordable.
       | https://www2.purpleair.com/
        
         | micheljansen wrote:
         | $200 for the cheapest model though. That's a factor 20!
        
       | Someone1234 wrote:
       | Informative article with fair, fact based, conclusions.
       | 
       | I'd like to add that:
       | 
       | - The VINDRIKTNING is extremely consumer accessible ($11.99, good
       | build, simple traffic light system).
       | 
       | - It may be put into spaces that previously had no particulate
       | air quality monitoring.
       | 
       | - The spouse-acceptance-factor is extremely high (unlike e.g. a
       | couple of circuit boards wired together off of Aliexpress).
       | 
       | There are other consumer friendly offerings, but they aren't
       | affordable (e.g. Amazon Smart Air Quality Monitor 4x cost,
       | Airthings 10x cost). That being said, IKEA could fix their
       | traffic-light system's cut off points for free and should
       | consider it.
        
         | azth wrote:
         | > - The spouse-acceptance-factor is extremely high (unlike e.g.
         | a couple of circuit boards wired together off of Aliexpress).
         | 
         | Which circuit boards do you recommend that have high accuracy
         | that can be ordered?
        
           | ahaucnx wrote:
           | I can recommed the Plantower 5003 PM sensor. Plantower also
           | has smaller ones, e.g. 7003 or A003 but we get the best (most
           | accurate and stable) readings from the 5003 model.
           | 
           | We also experienced with more expensive ones e.g. from
           | Sensirion but did not really measure a significant advantage
           | compared to the Plantower.
        
         | ahaucnx wrote:
         | It is actually pretty easy to build a much more accurate air
         | quality sensor with the Plantower PM2.5 module as a base and a
         | Wemos D1 mini as WiFi connected MCU. We have build instructions
         | on our website on how to do it [1] + a nice 3D printable
         | enclosure to pass the spouse-acceptance ;).
         | 
         | [1] https://www.airgradient.com/diy/
        
           | Someone1234 wrote:
           | I don't think our usages of "accessible" are the same.
           | 
           | For example expecting to consumers to have a 3D printer and
           | know how to use one would preclude it from my definition by a
           | lot. Let alone needing a breadboard and to manually solder on
           | components onto it.
           | 
           | Accessible is walking into a store, putting a reasonable
           | amount of money down, and plugging the thing in. Then
           | providing output anyone can understand without training or
           | expertise (e.g. traffic lights, smiley faces, etc).
        
             | zahma wrote:
             | Fortunately this is even easier:
             | https://sensor.community/en/sensors/
        
             | hedora wrote:
             | I once bought an air filter that had the pm 2.5 rating
             | surrounded by a blue/yellow/red halo. The only things it
             | was missing were logging, and the ability to run the sensor
             | without the fan. It could change fan speeds based on PM
             | 2.5, but it was calibrated for a small room, and always ran
             | way too slow.
             | 
             | I wish there were standards around thermostats these days.
             | If there were, then people could sell gizmos that measure
             | PM 2.5, then (if the windows are closed), use it to set the
             | speed of the variable speed blower in central air furnaces
             | accordingly. This would cut our electricity usage by at
             | least 20-30% during fire season.
             | 
             | (I'd love to see a legal mandate for interoperability in
             | this space.)
        
               | Tijdreiziger wrote:
               | > I wish there were standards around thermostats these
               | days.
               | 
               | https://en.wikipedia.org/wiki/OpenTherm
        
               | genewitch wrote:
               | My furnace blower isn't in use any longer, but it has
               | connections for varying speeds, 6, I think. It only uses
               | 1, though. I'm unsure of how it would even be used in
               | practice, as it appears it's just various voltages.
               | Ideally furnace blowers would be inverter ran so you
               | could just tell the inverter how fast to run the fan,
               | rather than changing the supply voltage.
               | 
               | Mine was a 3.5 ton HVAC, I replaced it with a five head,
               | five and a half ton "mini split"; while the split air has
               | had it's share of issues (like, I got a full refund of
               | the purchase price a few months ago due to manufacturing
               | defects of the copper lines), I prefer having air
               | handling done bear the ceiling and using 20x20x1 inch
               | filters on box fans (or fancy filters if those are your
               | style) on the floor. The mini split has the inverter
               | driven motors everywhere, and is completely silent during
               | normal use.
               | 
               | I have two AQM, and occasionally one or the other will
               | register high CO2 or whatever and I will open a couple of
               | windows and run exhaust fans (built in to the home) to
               | cycle the air, it takes about 20 minutes. The main
               | furnace style system did no filtering or air quality
               | management.
        
             | mellavora wrote:
             | to be fair, ahaucnx didn't use the word 'accessible', he
             | just said 'easy to build' -- and this is hacker news, not
             | consumer reports.
             | 
             | but if you do want 'accessible' in your sense of the word
             | (pay some money, get a working assembled unit), AirGradient
             | does sell assembled units. And can provide a back-end
             | system for remote monitoring if you would like.
        
               | Someone1234 wrote:
               | The comment was edited to remove the word. "Easy to
               | build" wasn't originally there.
        
           | formerly_proven wrote:
           | I see that there's a tiny 20x20 fan in these modules. Do
           | these make audible noise or are the fans in these running
           | rather slowly just to have air movement "better than
           | convection" through the sensor?
        
             | GekkePrutser wrote:
             | The person who did the original hack on these says they are
             | audible and the controller is constantly switching the fan
             | on and off so they reconnected it to 3.3v all the time. So
             | it runs at a lower speed and constantly.
             | 
             | See this link under the low noise mod heading
             | 
             | https://github.com/Hypfer/esp8266-vindriktning-particle-
             | sens...
        
         | beckingz wrote:
         | Spouse acceptance factor is an underrated engineering
         | constraint.
        
           | monopoledance wrote:
           | And likely an unnecessary sexist remark.
        
             | ev1 wrote:
             | No sex or gender was implied by the word spouse?
        
               | monopoledance wrote:
               | "technically, ..."
               | 
               | Yeah, I know. That's why I said likely. C'mon, don't play
               | stupid.
        
               | illumanaughty wrote:
               | What makes it likely when nothing about sex/gender is
               | mentioned? Seems like you're the one that has a gender
               | bias and you're projecting lol
        
               | monopoledance wrote:
               | Sure. Must be me projecting, because sexism in tech does
               | not exist.
               | 
               | > Spouse acceptance factor is an underrated engineering
               | constraint
               | 
               | So, tell me, how could this be interpreted without
               | implicit gender assumptions? Get creative, you got this!
        
               | simondotau wrote:
               | Can you explain why it would be sexist, even if we
               | applied mid-20th century framing to it? Why is it
               | degrading to describe someone as having a different
               | threshold of tolerance for aesthetics?
        
               | monopoledance wrote:
               | > having a different threshold of tolerance for
               | aesthetics
               | 
               | Lol. How you all trying hard to reframe it, to make it
               | sound innocent.
               | 
               | I am not going to explain shit. Look how y'all got
               | triggered, totally normal reaction... The original post
               | flagged... If you don't see the generalized "women/wives
               | don't like nerdy/tech stuff", there is no point to this.
        
               | UnFleshedOne wrote:
               | Well, but is it wrong? Even you knew which gender is less
               | likely to like bare baseboard with chips sticking out. Do
               | you expect people to actively disregard their lived
               | experience?
        
               | monopoledance wrote:
               | > Well, but is it wrong? Even you knew which gender is
               | less likely to like bare baseboard with chips sticking
               | out. Do you expect people to actively disregard their
               | lived experience
               | 
               | Thanks, for confirming it. Ridiculous, how everyone is
               | trying to bend interpretation.
        
         | LeanderK wrote:
         | I think being low-cost is very important, otherwise I wouldn't
         | consider it. I don't live near a major road, but in a small
         | city. I don't think the air-quality is bad, but I also don't
         | know for sure. I would not invest a significant amount of money
         | (more than 10-15EUR).
        
           | TheBlerch wrote:
           | You may find the Breezometer app helpful - I've found it
           | quite accurate for local outdoor air quality in several
           | different areas.
        
           | Someone1234 wrote:
           | I've found a lot of indoor sources of contaminants for
           | example cheese that fell off a Pizza onto the oven floor will
           | put you into "yellow" the next time you run the oven.
        
       | jve wrote:
       | Really glad this was published. I was looking at airgradient
       | solution for PM2.5 monitoring, but while thinking - saw this @
       | IKEA and bought it. And it is in my short term plan to wire it
       | with Wemos D1 so I plot values and make sense on whether IKEA air
       | purifier helps anything or not. Because if I follow the LEDs,
       | it's chaos - it can be RED for hours with purifier nearby. And
       | the same without purifier - colors just like to change in my
       | house.
       | 
       | I have a question about precision: If the precision +-20mg/m3 -
       | isn't it actually normal that they "extend" the green led up to
       | 35mg/m3 then? Because that 12mg/m3 is maybe 32? Uh, looks like
       | not even PMS5003 can reliably show you that green line with a
       | high confidence, doesn't it?
       | 
       | Btw here is a nice thread that shows you how to wire it up with
       | Wemos D1 and connect to Home Assistant. People compare their
       | readings with other meters, too. But someone says he bought
       | multiple of those and even those show different numbers. Someone
       | sees IEKA values 10x higher (for lower values, but within
       | specified accuracy) than other sensor https://community.home-
       | assistant.io/t/ikea-vindriktning-air-...
       | 
       | But at least they FOLLOW the plot of more accurate sensors. I see
       | value in that. I want to know if air purifier helps something or
       | how much it helps.
        
         | genewitch wrote:
         | As a quick aside, both the air quality things I bought say not
         | to rely on instantaneous readings but instead to use the
         | aggregator average reading. One has the ability to show
         | averages and the other is more like "if the value is
         | consistently higher than normal it's probably correctly 'high'"
         | - so unless there's some weirdness in the Ikea one it shouldn't
         | be switching colors unless you are very close to the threshold.
         | 
         | It is possible that your air filter shakes or vibrates enough
         | that it's kicking dust up, or you have poor indoor air quality.
         | How often do you have to replace filters and how dirty are
         | they? For reference I live in a forest, with pollen and dirt
         | dust and people and pet dust, poor seals on windows, and open
         | doors/screens, as well as high humidity year round; I buy the
         | 3M 1000-1500 filters which are pretty beefy, and they last
         | about two months before becoming uniformly dark grey on front
         | and back. Ideally I'd replace them monthly but they're about
         | $15 each and that adds up across three filters.
         | 
         | I ask because I don't think my system does anything for VOC, I
         | don't use carbon filters for the three, so I'm mostly filtering
         | dust, pollen, clay, etc.
        
           | jve wrote:
           | I bought this unit just ~2 weeks ago?
           | https://www.ikea.com/us/en/p/foernuftig-air-purifier-
           | black-6...
           | 
           | So I haven't had chance to change filters yet.
           | 
           | Yeah, but it has high outgoing airflow, so I suppose it
           | shakes up dust for me. It changes to red pretty fast when
           | starting to cook, then hours, hours to bring it down.
        
       | thecal wrote:
       | Direct link to the item:
       | https://www.ikea.com/us/en/p/vindriktning-air-quality-sensor...
        
       | GatorD42 wrote:
       | The color guides seem similar to the IQAir AirVisual Pro and
       | Apple's weather app. Like the article mentions this is likely to
       | be inside and most useful for alerting when cooking has caused
       | significant particle emissions, that's what I use my AirVisual
       | for.
        
       | [deleted]
        
       | maltalex wrote:
       | Say I'm convinced enough to order an AirGradient kit. Is this
       | accurate? Does it take up to 5 weeks for _most_ destinations?
       | 
       | > We currently ship approximately 1-2 weeks after receipt of
       | payments. Delivery takes 2-3 weeks to most destinations (North
       | America, Europe, Australia).
        
         | ahaucnx wrote:
         | The shipping times mentioned on the website are a bit
         | conservative and often it is faster.
         | 
         | We currently have kits in stock and ship within a few days of
         | orders received.
         | 
         | Shipping times really vary depending on destination and are
         | hard to predict but 2-3 weeks is a good estimation.
        
       | Foivos wrote:
       | For the price it is offered, it performs very well. I am not
       | aware of any other PM2.5 sensor at $10. It cheapest I have seen
       | is $40.
       | 
       | You can still use it to get a rough idea of your air quality and
       | it is definitely "better than nothing (or not having it)".
        
         | Semaphor wrote:
         | The one they use for their DIY Kit [0] actually costs $16-19
         | [0] at aliexpress
         | 
         | [0]: https://www.airgradient.com/diy/
         | 
         | [1]: https://www.aliexpress.com/item/32944660534.html
        
       | djanogo wrote:
       | Playing devil's advocate, this device is obviously made for mass
       | market($11.99), what if the WHO/AQI "Good" numbers are too hard
       | to achieve for general consumers?, the buyers of this device
       | might be venturing into clean air for the first time and the last
       | thing they want to see is "orange/red" ALL the time.
        
         | blacksmith_tb wrote:
         | I bought three Vindriktnings when they came out, and on a day
         | when we had some wildfire smoke making outdoor air quality
         | around 150 put all three outside. Two went yellow then red,
         | while the third stayed green... I guess I'd prefer a false
         | positive to a false negative personally. It's true, they only
         | cost me $13 each, so not a huge loss but it does suggest there
         | are quality control problems with either the sensor or the
         | whole device.
        
       | Animats wrote:
       | That's just particles. No CO2 sensor.
        
         | mpalczewski wrote:
         | Just to add to this:
         | 
         | CO2 is important because it is a proxy for how much air you are
         | rebreathing. This is especially important because of Covid. If
         | you have a few people in a poorly ventilated room co2 will
         | climb. Whereas in a well ventilated room, it might be nearly as
         | good as being outside.
         | 
         | Even for just being at home this is important because if the
         | air is poorly ventilated it will feel "stuffy". It can affect
         | how well you are able to think and work.
         | 
         | Most air quality meter's only measure pollution, and you have
         | to get an expensive one to measure co2 which is why it is
         | frequently omitted despite importance.
        
       | dsizzle wrote:
       | Does anybody have any stories of how devices like this revealed a
       | problem -- what the problem was, does an air filter fix it, etc?
        
         | kccqzy wrote:
         | There was a time when my air quality sensor (a Temtop device)
         | showed suspiciously high PM2.5 in the kitchen. It turned out
         | the kitchen oven had too much oil build up inside and required
         | cleaning. And no, I tried both cheap and expensive air
         | purifiers; none of them could beat opening the kitchen window
         | or turning on the range hood (a dedicated one, not the kind
         | attached to a microwave). In this particular case, it was also
         | a good reminder to clean the oven.
        
         | colechristensen wrote:
         | You would be surprised how much particulate certain cooking
         | methods produce, your home can go from 0 AQI to forest fire
         | levels for a few hours without a filter.
         | 
         | With the right filter and sensor, you can keep your AQI in the
         | single digits consistently and react appropriately to particle
         | buildup. If you have a CO2 sensor as well you can react to CO2
         | buildup which is something I have experienced plenty of times
         | in a modern apartment (not necessarily dangerous levels but
         | levels high enough that cognitive effects should be expected).
         | It is hard to keep indoor CO2 levels anywhere near outdoor
         | levels without forced ventilation with the outside or living in
         | a large house.
        
           | dsizzle wrote:
           | Do you have any recs for the right filter and sensor?
        
             | dylanz wrote:
             | Someone referred me to https://oransi.com/ and I purchased
             | one of the large EJ120 models. I've had it running for a
             | few days and my place no longer has a smell and the air
             | just feels clean. It's bizarre.
        
               | dsizzle wrote:
               | Doesn't look like any of those have sensors, unless I
               | missed that? I guess one sensor is your nose in this
               | case, ha.
        
               | amatecha wrote:
               | Nice, thanks for the recommendation. Is the EJ120 very
               | audible? Where do you place it? Like someone mentioned
               | elsewhere, the spouse approval factor is relevant for
               | what air filtration solution I go with... haha
        
           | kfarr wrote:
           | We have an indoor purple air sensor with a color gradient
           | indicator (from green all the way to purple and many
           | gradients in between). Exactly as you've said we are
           | surprised at the number of times cooking has turned the air
           | quality horrible indoors. Further we are able to see how when
           | air outside is smoky from wildfires that the internal air
           | filters are doing their job. Definitely worth the cost for us
           | in the Bay Area:
           | https://www2.purpleair.com/products/purpleair-pa-i-indoor
        
         | dirtyid wrote:
         | I have a xiaomi air purifier with AQ detector. Scrubber seems
         | to to help with allergies. Detector itself is pretty much a
         | glorified smoke detector Tamagotchi toy for me. I haven't found
         | much use for it other than to keep numbers as low / nominal as
         | I can. For which living in a pretty clean part of the city with
         | good air quality means being more mindful when I cook to reduce
         | smoke. That said the high AQ alarm has saved me a couple times
         | from leaving stove top on / burning pots. Kind of paid for
         | itself in that sense.
        
         | fma wrote:
         | Yes...formaldehyde exposure is a big issue in the US. Not many
         | know of it. I bought a new construction house, so it has new
         | carpet, paint, cabinets, wood flooring etc has an off gas
         | effect. I honestly it's criminal to allow builders to build
         | like this, or material to be manufactured like this. That "new
         | car" smell, that smell when you open up new furniture made of
         | plywood (the glue contains formaldehyde) .
         | 
         | There are threshold laws in the US and Europe. There are laws
         | from OSHA that regulate where you work - but no laws that
         | regular where you sleep! It's all driven by money, of
         | course...material with lower formaldehyde cost more to
         | manufacture. Just walk into a Sherwin Williams and compare
         | their paint. The highest ones are eco friendly "Low VOC"
         | (volatile organic compound) - so industry definitely knows
         | about it.
         | 
         | The numbers in my house were effectively off the charts and
         | OSHA would be closing down your employer if you had this
         | exposure at work.
         | 
         | Remediation for this is essentially allow to off gas, keep
         | windows open. Off gassing also is impacted by humidity, so may
         | be low during winter but high in the summer or when it rains.
         | 
         | Air filter DOES NOT fix this. The amount of air moved by a HVAC
         | is peanuts compared to just opening windows for a few minutes.
         | 
         | California has regulations: https://ww2.arb.ca.gov/our-
         | work/programs/composite-wood-prod...
        
       | AdrianoKF wrote:
       | I have a Vindriktning with the ESP8266 makeover sitting on the
       | desk behind me, feeding its data into my Home Assistant instance.
       | So far it's working great, except for one annoying detail: I'd
       | much prefer the forced airflow fan to be on at all times, since
       | the constant on-off cycling (around every ~10s) is quite audible
       | and distracting in a quiet environment.
        
         | solomonb wrote:
         | How do you know it is working great? Have you compared it
         | against other known sensors?
        
       | ortusdux wrote:
       | Does anyone know how amazon's new unit fares? It monitors PM 2.5,
       | CO, VOCs, temp, & humidity for 70$. I wouldn't buy one
       | considering the source, but I am interested in how effective it
       | is.
       | 
       | https://www.amazon.com/dp/B08W8KS8D3?&linkCode=ll1&tag=andro...
        
       | intrasight wrote:
       | http://energysmartohio.com/indoor-air-quality/which-indoor-a...
       | 
       | I've always returned to the Dylos sensor as the gold standard
       | 
       | Another good review of sensors: http://www.aqmd.gov/aq-
       | spec/evaluations/summary-pm
        
       | flybrand wrote:
       | I work at H&V - we're one of the biggest makers of air filter
       | media (the rolled goods / fabrics - not the actual filters).
       | 
       | We love seeing the innovation going on in this space - any
       | suggestions on how we could better support this growing awareness
       | of the value of IAQ?
        
         | dribblecup wrote:
         | Sponsor open source code and open source hardware solutions
         | that DIY folks can put together at $300 or below price point.
         | 
         | Gold star if you sponsor an independent test of this solution
         | to verify its effectiveness.
         | 
         | Bonus points for explaining what matters in terms of testing.
         | 
         | Self-serving (which is OK in this context) points for
         | explaining how your product mitigates the problem by
         | demonstrating the DIY metered results.
        
           | jve wrote:
           | I mean... first of all I would like to hear what are the
           | consequences of good/bad IAQ (Indoor Air Quality?)
           | 
           | I'm actually more driven/interested in data/compare it to
           | other folks, but I don't have a clue what does it mean for my
           | health. What's the difference between PM2.5, PM10, PM1,
           | PM0.1. What is TVOC (as in sensor description: benzene,etc
           | Volatile organic compounds), HCHO (is for formaldehyde). How
           | do I measure them (parent expands on these questions), what
           | are the "norms" and, most importantly: WHY should I care
           | about those values?
           | 
           | Then ofcourse tips on HOW to decrease those particles. That's
           | where filter comes in, yeah. First time someone said he just
           | slaps filter on an air ventilator, I was like: "Wow, it's SO
           | simple? Yeah, sounds logical"
        
       | zahma wrote:
       | I think I've plugged this here before. Sensor is an open
       | community trying to track pollution. You can build your own
       | sensor by ordering a dozen or so parts for 50-100 USD off
       | AliExpress or Amazon (or wherever else you'd prefer because
       | there's really nothing extraordinary here). Some sensors even go
       | down to 1 micrometer. The firmware is built to distinguish
       | between 1, 2.5, and 10 micrometers. I believe AQI is the standard
       | metric that is used for the map's visualization.
       | 
       | It requires minimal technical expertise, no 3D printing, no
       | soldering, and minimal configuration.
       | 
       | It's a noble mission, and I find the granularity of data for both
       | pollution and temperature far more telling than the estimates of
       | more centralized systems.
       | 
       | Check out the map and guide here:
       | 
       | https://sensor.community/
       | 
       | https://sensor.community/en/sensors/
        
         | rplnt wrote:
         | Looking at the map of EU, any idea why the hole in Czech
         | Republic?
        
         | dheera wrote:
         | I've been using a Adafruit Plantower PMSA003I and it always
         | reads 0 even if the AQI is 90 at my place.
         | 
         | It basically always reads 0 if the AQI is anywhere under 200,
         | and pretty useless.
         | 
         | I wonder if there is a better I2C sensor that I could use?
        
       | dahart wrote:
       | I don't think using the brand new WHO guidelines is very fair.
       | Not sure when it was released, but regardless this product was
       | likely completely designed and manufactured before the WHO
       | guidelines were published, just a few months ago.
       | 
       | Also, Airnow.gov still has a published scale that is _worse_ than
       | the IKEA product. https://www.airnow.gov/aqi/aqi-basics/. Green
       | is 0-50, Yellow is 51-100, Orange 101-150, and Red 151-200.
        
         | ahaucnx wrote:
         | Airnow is using US AQI and not mg/m. US AQI 50 corresponds to
         | approx. 12 mg/m.
        
           | dahart wrote:
           | Oh thank you, pre-coffee units fail on my part.
           | 
           | So I'd guess most air sensors on the market aren't
           | necessarily classifying their readings into green-good / red-
           | bad, or at least come with a now-outdated chart. Are there
           | sensors that have been released and/or updated to match the
           | new guidelines already?
        
       | punnerud wrote:
       | Archived version (from today):
       | https://web.archive.org/web/20211206144732/https://www.airgr...
        
       | dheera wrote:
       | I've been using a Adafruit Plantower PMSA003I and it always reads
       | 0 even if the AQI is 90 at my place.
       | 
       | It basically always reads 0 if the AQI is anywhere under 200, and
       | pretty useless.
        
       | prashnts wrote:
       | I have a question since the author is around:
       | 
       | My sensor was working fine for a few months. It's located near
       | the area I smoke, so whenever I'm smoking it changes to red
       | quickly. And after a few minutes (10 or so) it'd go back to
       | green.
       | 
       | But for past few weeks it's stuck at red. I disassembled it and
       | cleaned the intake hole (which is covered with a fabric) and it
       | worked after. However it went back to displaying red again all
       | the time.
       | 
       | So my question is whether this sensor needs frequent cleaning? If
       | so what are the alternatives?
        
         | renewiltord wrote:
         | Out of curiosity, and with no judgment intended, what is the
         | purpose of the air quality sensor if you are actively smoking?
         | Is it a mechanism for you to determine whether the smoking is
         | exposing other members of the household to second-hand smoke,
         | etc.?
         | 
         | I only ask because it seems to me (with no concrete research)
         | that the smoking risk is much greater than generalized air
         | quality risk.
        
         | ahaucnx wrote:
         | I don't really have much experience with the PM1006K in the
         | Ikea sensor but it is not untypical that PM sensors can get
         | "stuck" and showing high concentrations.
         | 
         | Sometimes it helps to blow compressed air inside to push out
         | any dust that might cover the optics but that also often does
         | not help too much or only temporary.
        
           | prashnts wrote:
           | Thank you! I'll try that. Building an airgradient sensor is
           | next in my list of projects!
        
           | skybrian wrote:
           | I've seen this and rebooting my Temtop sensor seems to help,
           | sometimes.
        
       | pnathan wrote:
       | When I was looking into air quality a year or two ago, I realized
       | that the color-coded "AQI" so popular are not precisely a
       | scientific analysis, as they are a blend of different
       | measurements, with cutoffs specified by committee. Different
       | countries have different formulas for AQI. That doesn't make them
       | wrong, but it makes them not a "gospel truth".
       | 
       | I have a Dylos rigged up inside my apartment, feeding particle
       | measurement data to a serial port, which stores the data on my
       | own cloud. I don't bother with AQI.
        
       | liversage wrote:
       | Some trivia: 'Vindriktning' is 'wind direction' in Swedish.
        
       | jerjerjer wrote:
       | Anything proven and with a better sensor quality?
        
       | ahaucnx wrote:
       | Author here. I forgot to mention:
       | 
       | With a Wemos D1 mini (ESP8266) MCU that costs around USD 2.00,
       | you can pretty easily make the Vindriktning WiFi connected and
       | get the data to a backend [1].
       | 
       | You just need to solder three wires, and there is enough space
       | within the enclosure to fit the D1 mini inside.
       | 
       | This would then allow you to get the exact measurements and to
       | better understand if the "green" is more on the lower end or the
       | higher side.
       | 
       | [1] https://github.com/Hypfer/esp8266-vindriktning-particle-
       | sens...
        
         | [deleted]
        
         | pingec wrote:
         | Are there any air quality devices that work well outdoors in
         | all kind of weather?
        
         | 404mm wrote:
         | Hi, thanks for the article!
         | 
         | Are there any non expensive sensors you could recommend? I care
         | about the indoor air quality but it gets very pricey. I have
         | Awair at home but it covers only one room and the unit runs
         | $300 a piece :(
        
           | ahaucnx wrote:
           | I am not aware of a good and low-cost wifi connected sensor
           | but as I mentioned it is relatively easy to build one
           | yourself.
           | 
           | If you don't want to buld yourself, there are a few
           | relatively good non-connected PM 2.5 sensors for example the
           | "SmartMi PM2.5 Air Quality Monitor" that I can recommend. It
           | costs around USD 30 here in Asia.
        
           | mellavora wrote:
           | I'm a fan of the airgradient, they offer a very nice DIY. You
           | can build a quality sensor for under $50.
           | 
           | https://www.airgradient.com/diy/
           | 
           | Components:                   Wemos D1 Mini USD 2.24
           | Wemos OLED display USD 2.47         Plantower PMS5003 PM
           | Sensor USD 13.89         Senseair S8 CO2 Sensor USD 28.00
           | SHT30 or SHT31 Temperature and Humidity Sensor Module USD
           | 2.55
           | 
           | I think the lead article was posted by the founder of
           | airgradient. I've had some email exchanges with him, he is
           | supportive and helpful.
        
             | geerlingguy wrote:
             | I can also attest to the inexpensive simplicity (and decent
             | reliability) of the AirGradient sensors.
        
           | bobiny wrote:
           | I like my Netatmo. I see that it costs $200 on Amazon for
           | main module + you can connect 3 additional ones for other
           | rooms -- they cost $86 each. It shows CO2 (notifies when it's
           | high on smartphone), temperature, relative humidity and noise
           | level.
        
             | [deleted]
        
           | ortusdux wrote:
           | I've been looking at ordering a variety of environmental
           | sensors from Seeed Studio's Grove line. They look
           | approachable and affordable, but I cannot vouch for their
           | quality.
           | 
           | https://www.seeedstudio.com/Grove-Laser-PM2-5-Sensor-
           | HM3301....
        
           | tnorthcutt wrote:
           | You might be interested in the author's DIY kits:
           | https://www.airgradient.com/diy
        
           | fossuser wrote:
           | Not the OP, but I tried a bunch of these and wrote up details
           | here: https://www.reddit.com/r/AirQuality/comments/ikf1ed/are
           | _ther...
           | 
           | Most of them (including the awair) are complete crap.
           | 
           | I found one that seems okay and is also one of the cheaper
           | ones.
           | 
           | I use and like this one best:
           | https://www.amazon.com/dp/B07DHXQXGK/
           | 
           | Simple screen with relevant details, no crappy 2.4ghz wifi,
           | no crappy app, etc. it just works.
        
             | noja wrote:
             | That looks like the Eve Room
             | https://www.evehome.com/en/eve-room
        
             | 404mm wrote:
             | Aqmd tested Awair and it came with really good results
             | actually. I'm struggling to find the report online at the
             | moment.
        
               | fossuser wrote:
               | It doesn't tell you AQI or PM2.5 so it's results may be
               | consistent but are fairly useless.
               | 
               | I'd be curious what report you saw, last I looked the
               | consistency of the results wasn't even that great either.
        
               | nitrogen wrote:
               | Awair's phone app lists both AQI and PM2.5, and PM2.5 is
               | available on the device itself by pressing buttons to
               | change the display. Somewhat confusingly, the indoor AQI
               | is on the Outdoor tab.
        
               | Matrixik wrote:
               | This one?: https://www.aqmd.gov/aq-
               | spec/evaluations/summary-pm
        
               | 404mm wrote:
               | Unfortunately no, not this one. I also came across these
               | but I recall a several page long reports for each device
               | individually. Tested in controlled environment and
               | compared with some professional $20k+ sensor. I wish I
               | could deliver better than promises lol.
        
           | ruffrey wrote:
           | I've used this one [1] then ordered similar ones from Ali
           | express after getting the Adafruit one working.
           | 
           | 1. https://www.adafruit.com/product/3686?gclid=CjwKCAiAhreNBh
           | AY...
        
             | stavros wrote:
             | I can second this one, I soldered four wires to connect it
             | to an ESP8266 and flashed ESPhome and that was it, it's
             | worked fine for months.
        
         | jb1991 wrote:
         | It would be great to hear some alternative suggestions for a
         | consumer air quality meter that is accurate, reliable. I.e. are
         | the AirThings products good? Or do you have any other
         | recommendations?
        
         | zibzab wrote:
         | Are you recording sensors output?
         | 
         | If the sensors have been calibrated in software, wouldn't you
         | get the uncalibrated values?
        
         | newman314 wrote:
         | Given that the correlation is pretty good, I wonder if it's
         | sufficient to just add a compensating factor to get a better
         | sense of air quality.
        
         | balaji1 wrote:
         | Should we just consider buying an air purifier?
         | 
         | Currently in Bay Area where air outside seems good but these
         | apartments seem poorly ventilated, old fixtures, old floors,
         | lots of electronics, etc.
        
         | namdnay wrote:
         | Nice article! One small typo:
         | 
         | > It can be seen that all three sensors correlate very well but
         | that the Vindriktning only shows about 65% of the PM2.5 values
         | of the other two sensors and thus seems to considerably
         | _understate the air quality_.
         | 
         | I think here you mean "overstate the air quality" right? Or
         | "understate the air pollution"
        
       | errcorrectcode wrote:
       | Nope, just nope. Ikea: purveyors of chemical-laden flat packs and
       | cheap, unrepairable items that don't last. PMS5003 modules are
       | much better (PM1, 2.5, and 10) and only cost $20. PM1 and 2.5 are
       | far more damaging to health than PM10.
        
         | Swenrekcah wrote:
         | Almost all furniture I've ever owned has been IKEA. With very
         | few exceptions they have all been very durable. Repairability
         | is excellent because everything is designed to be taken apart
         | by amateurs and spare parts are easily found. They are also
         | easy when moving because they can so easily be taken apart.
        
           | errcorrectcode wrote:
           | It wouldn't need spare parts if it didn't break. "Very
           | durable" compared to what since you have no experience with
           | anything else? Not solid wood furniture.
           | 
           | A table that weighs 8 lbs and costs 10 dollars should only be
           | used on a Hollywood set as breakaway furniture for safety.
           | 
           | You sound like you're rationalizing a religious tribe rather
           | than making a rational argument.
        
             | avh02 wrote:
             | > It wouldn't need spare parts if it didn't break
             | 
             | I guess you've never lost a single screw in your life.
        
               | errcorrectcode wrote:
               | Cheap shot. Maybe you shouldn't be commenting today.
        
               | [deleted]
        
             | maltalex wrote:
             | > You sound like you're rationalizing a religious tribe
             | rather than making a rational argument.
             | 
             | I can't believe that I find myself defending Ikea on HN,
             | but... what?
             | 
             | The parent's argument is very rational - in their
             | experience products have been durable, and the
             | repairability high for obvious reasons. What's religious
             | about that?
             | 
             | I owned several pieces of Ikea furniture myself, and some
             | were well made out of solid materials. Others were not.
             | Unsurprisingly, the material quality was strongly
             | correlated with the price of the item.
        
               | errcorrectcode wrote:
               | Myopia from limited experience is absurdly arrogant.
               | 
               | I have experience with O'Sullivan, IKEA, and fine
               | furniture like Stickley. You can't sand or paint sawdust
               | when it crumbles. If it gets wet, it's ruined. Fine
               | furniture often appreciates in value, while pressed dust
               | doesn't, falls apart when disassembled, and cannot be
               | economically repaired.
        
               | slantyyz wrote:
               | > falls apart when disassembled
               | 
               | Funny, in the 30+ years that I've had IKEA furniture,
               | I've moved several times. That you can disassemble IKEA
               | furniture is a benefit when moving, and I've had no
               | issues disassembling and reassembling multiple times.
        
             | slantyyz wrote:
             | > You sound like you're rationalizing a religious tribe
             | rather than making a rational argument.
             | 
             | So do you, actually.
             | 
             | IKEA has products of varying price points. Yeah some of the
             | cheap stuff might be pretty bad. Having said that, I have
             | family members with IKEA furniture that is now around 30
             | years old without issues.
             | 
             | I have expensive solid wood furniture as well as IKEA
             | furniture. Some of my own IKEA pieces that I bought after
             | finishing uni have lasted 30 years and are still in use. I
             | don't think I've thrown any IKEA furniture out, only passed
             | them on to other people.
        
               | errcorrectcode wrote:
               | You're appear to be seeking conflict with a lame,
               | baseless, personal attack because you are also a part of
               | that cult and can't handle criticism.
               | 
               | 30 years is nothing. I have 200 year old solid wood
               | furniture. I seriously doubt anything made from sawdust
               | will ever last that long.
               | 
               | I hope you and your family enjoy your IKEA decor.
        
               | slantyyz wrote:
               | > You're appear to be seeking conflict with a lame,
               | baseless, personal attack because you are also a part of
               | that cult and can't handle criticism.
               | 
               | Um, ok. I guess you got me there.
               | 
               | > 30 years is nothing. I have 200 year old solid wood
               | furniture. I seriously doubt anything made from sawdust
               | will ever last that long.
               | 
               | Ok, good for you then? I don't need anything to last 200
               | years, but I wouldn't be surprised if my sawdust
               | furniture lasts longer than me, since I take pretty good
               | care of my furniture.
               | 
               | > I hope you and your family enjoy your IKEA decor.
               | 
               | Yep.
        
         | hedora wrote:
         | Ikea has multiple price tiers (e.g. "good", better, best). The
         | bottom tier is basically disposable dorm furniture, which is
         | likely to be ruined/tossed anyway. Move up a tier if you want
         | something that's cheaper than other alternatives and lasts.
         | 
         | The only thing I've found that competes with their mid tier is
         | used furniture. (Which is obviously better for the environment
         | than buying new.)
        
           | mnw21cam wrote:
           | I have a folding dining table from ikea. It's %&(*! heavy,
           | surprisingly so for a small table, and is solid wood. It has
           | already lasted 15 years and I can see it lasting another 100.
           | 
           | Agreed, ikea sells some flimsy stuff, but they also sell some
           | really solid stuff.
        
           | robin_reala wrote:
           | [Disclaimer: IKEA employee]
           | 
           | We've got buy back / resale programmes globally, and the US
           | trialled it a couple of months ago. I'd expect to see this
           | expand over time.
           | 
           | https://www.ikea.com/us/en/newsroom/corporate-news/ikea-
           | us-h...
        
             | hedora wrote:
             | Oh wow, that's great! The less resources Ikea consumes, the
             | better.
             | 
             | However, I was referring to Craigslist "free" listings and
             | antique shops. I suspect those will continue to win out on
             | price or craftsmanship over most stuff Ikea sells. It's
             | hard to beat items that are free and/or hand-crafted from
             | old growth hardwood.
             | 
             | Our house is split roughly evenly between free stuff,
             | antiques, and ikea stuff.
        
           | handrous wrote:
           | I can only assume people who complain about Ikea--price,
           | assembly instructions, quality, et c.--have never experienced
           | other flat-pack furniture, like what Wal-Mart or Target
           | stock, which is worse on _all_ of those measures. Or most
           | bulky, ugly, fake-fancy big box furniture, even not flat-
           | packed.
           | 
           | I can only beat them on quality-per-dollar by going used, as
           | you note--mid-century-modern used furniture is expensive (and
           | is what a lot of Ikea stuff is designed after) but anything
           | earlier or later is usually very cheap.
           | 
           | Brands that consistently provide better quality for non-flat-
           | pack furniture tend to be _way_ more expensive than Ikea,
           | outside the range of what most normal folks are even
           | considering.
           | 
           | And yeah, it's true that their cheapest tier is practically
           | disposable, but it's hard to complain when an end table costs
           | $20 or whatever. Of course it's not gonna last decades, at
           | that price.
        
       | stdbrouw wrote:
       | The choice to display anything under 35 mg/m3 as "good" does not
       | seem unreasonable at first glance. Indoor PM2.5 can often be
       | higher than outdoor so that the yearly average will be pushed
       | down by time spent outside and there is no need to have <5 mg/m3
       | inside too. Also, by the author's admission the unit also
       | measures particles larger than PM2.5 which are less harmful.
       | There's no point in having a unit that will flash orange or red
       | for almost everyone almost all of the time.
        
         | ahaucnx wrote:
         | As I mentioned in the article it really depends on the length
         | of the exposure and how you use the sensor.
         | 
         | Yes in many places in Europe or North America, the outdoor air
         | quality is most of the time good.
         | 
         | However -unfortunately- there are also many places where the
         | outdoor air quality is very unhealthy most year round and then
         | an annual exposure to 35 mg/m3 vs 5 mg/m3 makes a big
         | difference.
        
           | aaron695 wrote:
           | > the outdoor air quality is most of the time good.
           | 
           | This is the point, knowing when it's bad so you can change
           | behaviour?
           | 
           | When does it spike in a forest? You'd guess when it's windy?
           | But is it seasonal? Does dust matter more the pollen, I think
           | pollen is more PM 10. Salt from the sea breeze is bad
           | (PM2.5), how does that mix with leaf matter in Fall?
           | 
           | > Indoor PM2.5 can often be higher than outdoor so that the
           | yearly average will be pushed down by time spent outside and
           | there is no need to have <5 mg/m3 inside too.
           | 
           | This line form OP is totally incorrect.
           | 
           | Indoors should be less than outdoors, unless you have a fire
           | or smoke indoors.
           | 
           | And why does "yearly average" matter? Smoking cigarettes
           | (which is exactly the same as what we are talking about) is
           | not about a "yearly average".
        
         | srg0 wrote:
         | I think it was a conscious design decision to reduce false
         | alarm rate. Assuming that this low cost device can be/become
         | very inaccurate, then the designers had two choices:
         | 
         | 1) Report all alarms as detected. Eventually, the device
         | becomes a red LED which users learn to ignore.
         | 
         | 2) Report a problem when the device is reasonably sure there is
         | a problem. Green light does not necessarily mean that the air
         | quality is good, but when the LED becomes red, it should be
         | taken seriously.
        
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