[HN Gopher] Reverse engineering Xiaomi air purifier NFC stickers
___________________________________________________________________
 
Reverse engineering Xiaomi air purifier NFC stickers
 
Author : thunderbong
Score  : 166 points
Date   : 2022-05-28 14:00 UTC (8 hours ago)
 
web link (www.flamingo-tech.nl)
w3m dump (www.flamingo-tech.nl)
 
| occz wrote:
| Good stuff. The author of the post has also previously made a
| defeat device that can fairly simply be installed in your
| purifier, which simply reports the filter to always be at 100%.
| Useful if you're in a place where the filter will last
| significantly longer than what Xiaomi thinks. I bought one and it
| works great, I can definitely recommend it.
 
  | KennyBlanken wrote:
  | Or just buy a unit from one of the companies that doesn't
  | engage in DRM nonsense.
  | 
  | Coway and Winex both do not do this and make top-rated units.
 
| causality0 wrote:
| Interesting. The concept seems obvious but this is the first I've
| heard of air purifiers using printer-cartridge style artificial
| scarcity.
 
| BasilPH wrote:
| I've built dynomight's DIY filter[^1], and I love it. No DRM
| issues either.
| 
| [^1]: https://dynomight.net/better-DIY-air-purifier.html
 
  | Someone1234 wrote:
  | Very cool. Anyone seen a mod that adds activated carbon? A lot
  | of DIY filters are very cost-effective, but the lack of
  | activated carbon is a big downside compared to commercial
  | solutions.
  | 
  | There's really only two air cleaning technologies that are
  | worthwhile right now:
  | 
  | - HEPA filters (remove PM 2.5 particulate and above).
  | 
  | - Activated carbon (neutralizes harmful gases).
  | 
  | The only other thing that may be worthwhile is a pre-filter,
  | but that is mostly a cost saving measure rather than actually
  | improving air filtration.
  | 
  | Unfortunately commercial filters are full of gimmicks that
  | don't work or may even be harmful due to Ozone generation (e.g.
  | Ionizers, UV lights, et al.).
 
    | papercrane wrote:
    | You could buy an activated charcoal filter built to attach to
    | the same inline fan booster from most garden stores that
    | carry indoor growing equipment. They're popular with people
    | growing cannabis indoors to remove the smell from their grow
    | area.
    | 
    | Something like this:
    | 
    | https://www.amazon.com/dp/B07GSKFBL8/
 
  | joshvm wrote:
  | Perhaps a stupid question. Why go to the trouble of bolting
  | together four filters, instead of attaching the duct fan to a
  | cylindrical HEPA filter? Then you just need two plates: one to
  | adapt the duct inlet and one to seal the base of the filter.
  | 
  | I think, as with many DIY projects, one must look to the pot
  | growing community. They solved the problem of "how do I not
  | stink out my apartment" a long time ago - duct fans and
  | HEPA/carbon filters are the mainstay of grow rooms.
 
    | bsder wrote:
    | Link? I'm interested.
    | 
    | However, I suspect availability plays into it. Almost anyone
    | can pick up a couple of rectangular HEPA filters and a box
    | fan from the local hardware or big box store.
    | 
    | I've never seen a cylidrical HEPA filter. So, I probably need
    | to order that from an industrial supplier.
    | 
    | And, aren't duct fans kind of noisy? Do they make quiet ones?
    | 
    | In addition, this fan/filter seems even easier:
    | https://smartairfilters.com/en/blog/cannon/
 
      | joshvm wrote:
      | The duct fan + filter combo is how lots of cylindrical
      | consumer units work (e.g. Levoit, Philips, etc). They just
      | use crappy fans which don't really pull any air through, or
      | they're very expensive for what they are. In terms of
      | availability, I think the current popularity helped,
      | otherwise you could also look at the auto market, lots of
      | cylindrical filters there and they'd be fine for pulling
      | out stuff like pollen, though you might want a carbon
      | filter as well.
      | 
      | I have no idea what's required for HEPA certification, but
      | lots claim to be:
      | 
      | https://www.amazon.com/LEVOIT-Core-Replacement-High-
      | Efficien...
      | 
      | It has an outer dust mesh, the HEPA filter and a carbon
      | insert. They're all the same though, I think you could use
      | any manufacturer's filter. Longevity isn't really an issue
      | if a supplier goes bust, just re-make the adapter ring.
      | Pretty much all you need and you don't need to worry about
      | sealing the corners.
      | 
      | According to OP's link, they use a duct fan booster which
      | is a lot quieter than a box fan (at least the claim is it
      | can go down to 16 dB).
      | 
      | Though a question is does a can-shape system work better?
      | Or would you get the same effect if you used a single flat
      | filter with the same "unrolled" area? I have no idea, and
      | there's so much uncertainty involved with DIY testing.
 
      | jrochkind1 wrote:
      | Hm, I feel like cylindrical HEPA filters are common for
      | shop vacs and widely available? Searching "HEPA filter shop
      | vac" on home depot gets what looks like plenty; or are
      | these not what would work for that kind of design, maybe
      | we're talking about different things? They are
      | "cylindrical" by being pleated.
 
    | kortex wrote:
    | Cost and availability. Cylinder filters tend to be way more
    | expensive ($30-50 per, I've seen true HEPA cylinder ones "for
    | allergy sufferers" aka medical space, >$130) than rectangular
    | (a few bucks). Rectangular also comes in a wider variety of
    | form factors than cylinders, with more different filter
    | styles (eg different thickness, with carbon, high flow, true
    | HEPA/MERV >13).
 
  | someotherperson wrote:
  | I go back to that page often. I might finally buy the parts
  | tonight and actually make it instead of just thinking about it
  | :)
 
| random3 wrote:
| Can someone explain what's the result of filter utilization /
| capacity. Is it efficiency? Does it start spilling out particles?
| 
| I feel like a 100% used filter will still do a pretty good job,
| so unclear how much of the utilization % has commercial
| reasoning?
 
  | sschueller wrote:
  | My assumption is that a "Full" filter has a reduced airflow
  | which means the fan pulling air in has to work harder. If it is
  | spected very tight then I could see it failing more quickly.
 
  | Waterluvian wrote:
  | My intuition is that the more "full" it is, the less air will
  | flow through it, meaning it just doesn't do as much.
  | 
  | Not to suggest that what the manufacture decides "100%" is is
  | actually that.
 
    | oh_sigh wrote:
    | That's exactly right for HEPA filters, not sure about other
    | types of filters though.
 
      | thaeli wrote:
      | This applies for any media filter. VFD drive on the motor
      | can keep airflow constant and increase energy usage
      | instead, but for most fans the increase in static pressure
      | means less air volume. Heavily loaded filters can also have
      | more air bypassing the filter, which may or may not be
      | significant depending on the application. For this kind of
      | air filter bypass just subtracts from the airflow through
      | the filter media.
 
  | KennyBlanken wrote:
  | Efficiency in terms of airflow goes down, and static pressure
  | difference goes up - but the filters trap more of the particles
  | going through them. Changing filters on furnaces and AC units
  | is really important, since lack of airflow hurts efficiency.
  | 
  | Wirecutter (which is usually trash) confirmed this in testing;
  | versions of units that had been running for months or longer
  | (ie one they bought a year ago and used in someone's home, vs a
  | new unit bought new with little run time) tended to perform
  | better in terms of how many particles they completely removed.
  | 
  | The unit starts using more electricity to do the same work, has
  | to run at higher fan speeds, etc. So it's a tradeoff between
  | that and the cost and waste generated by buying more filters.
 
    | ehPReth wrote:
    | curious - why is Wirecutter trash? I've been sorta feeling
    | iffy about them for no real reasons but they seem highly
    | recommended
 
      | inferiorhuman wrote:
      | With air purifiers at least Wirecutter completely ignores
      | known problems in order to collect sweet, sweet referral
      | fees. Comments about the high levels of VOCs in some
      | brands' filters, fans exploding, etc. all get/got ignored.
      | 
      | In my case I bought a couple Coway air purifiers only to
      | find that Coway doesn't honor their warranty. I hit all the
      | common complaints from the comments section - comments
      | Wirecutter staff refuse to acknowledge.
 
      | lostlogin wrote:
      | I was reading their list of coffee grinder recommendations.
      | Some they recommend I got rid of years ago as they aren't
      | very good. It may be the case that they had a price
      | ceiling, as the article mentions how costly grinders are,
      | but it's certainly dropped my opinion of Wirecutter.
 
      | rhexs wrote:
      | They almost always conveniently only recommend products
      | that allow for referral fees.
 
        | aardvarkr wrote:
        | The product manufacturers don't pay referral fees, it's
        | the retailer. So your entire argument against them is
        | you're mad they make money by linking to Amazon or
        | target?
 
        | wincy wrote:
        | I'd definitely prefer something like Consumer Reports who
        | has the budget to expose scams like Molekule who claim to
        | invent some magical new type of air purification.
 
        | inferiorhuman wrote:
        | > So your entire argument against them is you're mad they
        | make money by linking to Amazon or target?
        | 
        | That's not my entire problem with them, but it's a
        | problem. Because they're reliant on referral fees their
        | motivation is purely to get you to buy random crap
        | whether or not it's any good. So long as their reputation
        | holds up that's good, but once they start promoting crap
        | there's going to be a long tail of folks who think "oh
        | it's on wirecutter, it must be good".
        | 
        | Take a look at their reviews. It's not that they promote
        | stuff that they might get a kickback on, Wirecutter
        | _only_ promotes stuff they can generate a referral link
        | to.
 
        | [deleted]
 
        | eli wrote:
        | so pretty much anything sold by a major retailer?
 
      | SemAntics0 wrote:
      | Years ago, they really drilled into the performance of the
      | various products they compared and frequently the winner
      | was a specialist product from a brand you had never heard
      | of, but it really was the best on the market. Wirecutter
      | articles did good testing with defined rationale that might
      | not be up to laboratory standards, but it was enough to
      | clearly identify which products were offering the best
      | performance. When they labeled a product "The Best X", you
      | could be fairly confident that it was going to outperform
      | almost everything else on the market. They tested
      | everything from the highest range products to the garbage
      | chinesium specials and if you read the entire article, you
      | could see where some products might outperform in certain
      | areas, but under perform in others, letting you make an
      | informed decision that wasn't simply picking the "Winner".
      | Effort had clearly been put into discovering a full range
      | of products instead of simply comparing the amazon options.
      | Any product that was disqualified from comparison had a
      | clear and reasonable rationale.
      | 
      | Starting around 2018 the quality of testing plummeted into
      | clickbait territory. Many articles appeared to justify
      | their choices entirely based on reading amazon reviews
      | without actually putting hands on the product, a theory
      | reinforced by waves of comments appearing that despite a
      | wirecutter recommendation, the product was absolute junk.
      | My personal "Wirecutter is a lost cause" moment was when I
      | was looking for a new comforter and the writer had simply
      | disqualified every single option that was polyester based
      | because "I don't like how polyester feels." That's not good
      | testing. That's opinion. If I wanted subjective opinions on
      | products I wouldn't be at Wirecutter.
      | 
      | For an contemporary example, pull up their "The Best Drill"
      | article. The reviews highlight things you could discover
      | from holding the drill and looking at it. The testing is a
      | single test performed by a single person with no edge cases
      | or alternative uses considered. If ergonomics are such a
      | critical consideration that it gets entries shot down,
      | shouldn't you have multiple people testing to see how
      | different models perform in different people's hands?
      | Furthermore, the only products tested are mid-range
      | household drills available from big box stores. Nothing
      | from the professional brands like Festool or Hilti or some
      | brand I've never heard of. No explanation why I shouldn't
      | just buy a Harbor Freight special for half the price. No
      | explanation why any other consumer-grade brands weren't
      | included. The articles don't provide "The best drill",
      | they're providing "The best consumer-grade drill for light
      | duty work", and this attitude has spread to every corner of
      | the site. You can't go to wirecutter and find a specialist
      | tool that outperforms the commonly available options any
      | more, because they're not even including it in testing.
 
        | diziet wrote:
        | The Best Drill article doesn't even mention impact
        | drivers, which are going to be tremendously easier on the
        | wrist/hand for screwing in screws. An explanation for the
        | lay audience would help. Nor are questions such as: "How
        | much torque is there? What is the torque curve? How much
        | torque do you need? Do you need a hammer drill? What is
        | the noise like?" addressed.
        | 
        | I do think more specialty gear is hard to cover, as for
        | example the the impact driver here:
        | https://www.youtube.com/watch?v=l_pCeGmQU8w or AvE's
        | youtube coverage of tools goes beyond that. Project Farm
        | tends to have better coverage of general equipment with
        | pretty good objective tests:
        | https://www.youtube.com/channel/UC2rzsm1Qi6N1X-wuOg_p0Ng
        | but even he can't cover all the brands/models: He covered
        | Festool but not Hilti's SF 2H-A Hammer, for example.
        | 
        | Techgearlab has pretty unbiased coverage, and they also
        | have an small incentive to cover products that have
        | affiliate programs -- however, for example their parent
        | rock climbing site Crash Pad Coverage:
        | https://www.outdoorgearlab.com/topics/climbing/best-
        | boulderi... includes Organic pads which have no affiliate
        | program.
 
  | 5e92cb50239222b wrote:
  | I live in an very polluted area (average PM2.5 level in winter
  | around 300 ug/m3) and have been running the same filter non-
  | stop in a cheapest Xiaomi purifier for 1.5 years. It's almost
  | black, but works fine, as confirmed by DIY PM sensors. I think
  | it puts more strain on the motor, but I don't see any
  | difference in efficiency.
 
| jrockway wrote:
| The big problem I see with DRM on air filters is that air filters
| don't do anything complicated. Remove the electronics module and
| connect the fan directly to power. Done. They should have done
| that in the factory and pocketed the profit from not buying
| electronics and NRE.
| 
| (This is less possible on things like printers, which have to
| synthesize somewhat complicated motion, carefully release ink at
| the right time, etc.)
 
| rbrtdrmpc- wrote:
| This is nice! And the timing is perfect for my purifier to
| complain about the second filter that I've so far
 
| iSloth wrote:
| I've never experienced an air purifier, what's the general
| consensus?
| 
| Do they make a difference? Perhaps a placebo? A must have?
| 
| Genuinely interested if I'm missing out - For what it's worth I
| do live right on a main road in the UK, so I expect there is some
| level of pollution in the air.
 
  | legulere wrote:
  | The soot they filter out of the air is very visible when you
  | change the filters (they turn from shining white to grey). Air
  | pollution is one of the world's leading risk factors for death
  | https://ourworldindata.org/air-pollution#air-pollution-is-on...
  | . Though that varies a lot from country to country, it is a
  | problem you can strongly reduce with throwing a tiny bit of
  | money on it.
 
    | gruez wrote:
    | If the filter is only turning Greg it sounds like what you're
    | seeing is dust rather than soot. I have a pm2.5 meter and
    | over the winter/spring the reading is almost always 0 or low
    | single digits, and my filters still turn grey
 
  | DragonStrength wrote:
  | The biggest effect is in homes without any sort of central air
  | system, which would usually include various levels of filters
  | up to HEPA and UV systems at this point. During the worst of
  | fire season in the Bay Area though, a single Coway HEPA filter,
  | basically a box fan with a HEPA filter strapped to it, kept my
  | apartment in the "safe" range for AQI. Just stepping out my apt
  | front door into the hallway I'd be hit with the heavy stench of
  | smoke.
  | 
  | Truly remarkable how well they work, but whether you need one
  | or not depends on whether you have allergens/pollution as an
  | issue in your home. You can purchase an air quality monitor (I
  | have a Temtop M10) or check online measurements of AQI, pollen,
  | etc. for your area. If you have an issue, they work, but not
  | everyone has an issue.
 
    | techwiz137 wrote:
    | Okay so I bought a cheap-ish Air Purifier, now because the
    | brand is...I think it's Chinese(Rohnsonn), I can't determine
    | if it really does anything, if these filters do anything at
    | all to improve my air quality and if the UV light is even
    | strong enough to kill germs. Is there a way to verify it's
    | effectiveness?
 
      | DragonStrength wrote:
      | I'd look at what the purifier claims to eliminate and find
      | a quality monitor that will give you a reading. Most are
      | portable, so you can compare to outdoor values directly.
      | You're going to need some baseline to compare to though. If
      | you have an AQI in the safe range already in your home,
      | you'd have to contrive some actual experiments or find
      | someone who already has.
      | 
      | I'll say I'm pretty distrustful of anything but filters
      | personally. My mom purchased a purifier at one point which
      | claimed to use UV light to purify but had no fan to
      | actually pull air through the light, so obviously, it
      | wasn't doing anything.
 
  | jaqalopes wrote:
  | Ancedotally they work 100%. Not only do they remove noticeable
  | odors, they suck up tons of allergenic dust and invisible
  | particulates that can mess with your breathing (if you have a
  | sensitive respiratory system).
  | 
  | Non-anecdotally, I've heard it claimed that indoor air
  | pollution is the #1 factor in reducing the lifespans of
  | otherwise healthy people. No idea if this is the case or what
  | the evidence is, but I don't find it hard to believe.
 
    | Rastonbury wrote:
    | In developing countries they have poor stoves at home which
    | give of smoke/CO which is harmful aka indoor air pollution. A
    | good easy way to prevents deaths/harm from these is to
    | provide them with quality stoves. So depending on where you
    | heard it, air pollution could mean these stoves which typical
    | don't exist in the developed world
 
      | Rebelgecko wrote:
      | Even in developed countries, I think most homes still have
      | gas stoves which are bad for indoor air quality.
 
      | legulere wrote:
      | Frying things even on induction still easily drives
      | particulate matter pollution to levels of bad days in
      | China/India.
 
  | azuredragon wrote:
  | They also double as a mosquito trap. I used to suffer
  | persistent mosquito annoyance at night, but, since I got an air
  | filter, the problem is gone. I often clean out dead mosquitos
  | from the air filter
 
  | hammock wrote:
  | I was so skeptical. Living in SF in 2018(?) during the
  | wildfires, my apartment was drafty and I'd come home from work
  | to a hazy indoor environment. I'd wake up with a sore throat
  | and that's what got me to take action (can't sleep with an n95
  | on)
  | 
  | I got the cheapest air purifier from Amazon and just put it on
  | my bedside table. After one night my sore throat was gone.
  | 
  | As simple as these machines are, they do work.
 
    | CoastalCoder wrote:
    | I can see how an air purifier makes sense in that 2018
    | scenario.
    | 
    | I guessing that the benefits are less certain in more typical
    | cases.
 
      | AlotOfReading wrote:
      | Higher air pollution, especially during childhood, is also
      | strongly linked to the development of asthma and other
      | respiratory issues later in life. Pretty much everyone
      | should at least be aware of their home air quality.
 
      | hammock wrote:
      | The benefits, yes. Those would be dependent on the local
      | environment and if it's causing you specific suffering. But
      | that experience sold me on the functionality at least.
 
      | imajoredinecon wrote:
      | > that 2018 scenario
      | 
      | It's a little hard to believe if you haven't lived there
      | recently, but basically the entire US west coast now has an
      | annual fire season where you can expect at least several
      | days of air quality in the "unhealthy" to "hazardous"
      | range. AC (which does ~the same thing for air quality as a
      | purifier) or a purifier is pretty much mandatory.
 
        | samstave wrote:
        | When the fires were raging, I was looking at all the
        | areas air quality from purple air monitors and some areas
        | near folsom California were at ~700
        | 
        | And healthy is something like <100
 
  | haunter wrote:
  | My parents live in a very old house (~1700s) and it reduced the
  | dust significantly. Not perfect but maybe it's on the model
  | too. Like it's not an $1000 one which would probably work much
  | better
 
    | input_sh wrote:
    | They're pretty much all the same, just a fan in front of a
    | HEPA filter. If you can get a square fan and tape a HEPA
    | filter in front of it you'd get pretty much the same result
    | as many modern air purifiers.
    | 
    | You're paying for convenience and some bells and whistles
    | (like a mobile app and an air quality reader), but the
    | underlying technology behind it is pretty bare-bones, heavily
    | tested, and heavily used in industrial applications.
 
  | arinlen wrote:
  | > _Do they make a difference? Perhaps a placebo? A must have?_
  | 
  | It really depends on where you're coming from.
  | 
  | I have one of those air purifiers from Ikea (Fornuftig). It's
  | cheap but not the cheapest. On any high dust/polen
  | concentration level day, a minute or so with the device turned
  | on at full blast is enough to make any problem go away in that
  | particular room.
 
  | dxhdr wrote:
  | > Do they make a difference? Perhaps a placebo? A must have?
  | 
  | Purchase an air quality monitor, something like the Dylos
  | DC1100. Then run a HEPA filter in a closed room for 30 minutes.
  | It will remove almost all particulates! They work extremely
  | well. Whether it "makes a difference" for your health is less
  | clear.
 
    | criddell wrote:
    | Are the lower priced options on Amazon junk compared to the
    | DC1100? I'd like to get a monitor, but I know I'll probably
    | only use it 10 times. The Dylos would end up being about $25
    | / reading...
 
      | dxhdr wrote:
      | Good question, I bought a Dylos back in 2015 and can't
      | remember how the other options stacked up when I researched
      | it. I've been happy with the purchase and would recommend
      | it if you're interested in watching air quality. It has a
      | convenient "monitor mode" where it will re-sample the air
      | every hour so it's not constantly running. It's neat to see
      | how the air quality in a room changes based on having the
      | windows open or shut, after cooking, just being in the
      | room, etc.
      | 
      | I'd expect there are smaller / sleeker / more advanced
      | monitors out now though. Generally speaking I think you
      | want a laser detector instead of the cheaper infrared
      | detectors.
 
        | criddell wrote:
        | I found this link with test results:
        | 
        | https://www.aqmd.gov/aq-spec/evaluations/summary-pm
 
  | trompetenaccoun wrote:
  | If you don't understand the purpose, it means you don't need it
  | - as so often. The reason they exist is that in some parts of
  | the world the air is so bad it literally has significant
  | negative health effects just breathing it. That's why people
  | use them, and for what it's worth as far as I understand the
  | quality ones do work, in the sense that you can use an air
  | quality meter and detect a noticeable improvement in air
  | quality. They have filters that you need to change regularly.
  | 
  | -Edit- Since so many people are raving about them and
  | recommending you buying an air purifier I want to add this: If
  | you live in a place where the air is truly that bad, my main
  | recommendation would be to move. I have personal experience
  | with this, it's not worth it living like that. You may filter
  | the air in your home but then whenever you go outside you're at
  | risk, if you do sports even more so. Some people wear surgical
  | or cheap cloth masks but these don't actually work.
  | 
  | Don't listen to people who tell you that you can "see"
  | pollution of "feel" the difference. I've lived in some of the
  | most polluted cities in the world and the truth is in most
  | cases for regular healthy people they don't notice anything for
  | years, even at pollution levels far beyond the imagination of
  | folks in Western countries. Most of this is their imagination
  | or placebo like you suspect. For example I've had people
  | complain to me that the air is "so bad" in a place that's
  | naturally foggy and where visibility is often low, but had good
  | air quality. Others were happy about the lovely "clean" skys in
  | a city that gets lots of sunshine but was actually horribly
  | polluted. Also sure, smoke from wildfires is visible (and short
  | lived) but a lot of the pollution from industrial sources
  | isn't. It's a slow and stealthy killer.
 
  | radicality wrote:
  | I recently got a Medify Air MA 125 after a lot of research. Can
  | recommend the brand.
  | 
  | And yes it definitely makes a difference. Sometimes when I open
  | my windows to get some "fresh" air and remove the co2 from my
  | room, the ppm momentarily goes up. Also very useful for cooking
  | since I don't have a great vent. Ocassionaly when frying
  | something ppm goes over 200 but it quickly drops down with the
  | air filter.
 
  | KennyBlanken wrote:
  | If you have central air heating/AC and a vacuum cleaner that
  | has a hepa bag, you likely don't need one; just buy filters
  | that aren't the blue spiderweb kind and vacuum regularly.
 
    | dzhiurgis wrote:
    | HRV frequently has filters too
 
  | ms4720 wrote:
  | Depends on a few things:
  | 
  | 1. what that particular filter filters out: ppm, mold,
  | chemicals 2. What is in the air being filtered 3. How sensitive
  | you are to the things in your air 4. How often the rooms air
  | gets filtered through the filter 5. How effective the filter is
  | 
  | I worked in Beijing for a while and going somewhere with
  | filtered air literally felt like a weight was removed some
  | days.
 
  | Joeri wrote:
  | We live in the city and always are struggling with allergies.
  | The whole family is always coughing or sneezing. We bought a
  | xiaomi air purifier like in the article last week, started
  | using it in the bedrooms for a few hours in the evening, and
  | the allergies cleared up overnight. The particulate sensor is
  | mostly useless, a known problem with the xiaomi models, but
  | running it at a fixed setting seems to clean the air quite
  | effectively.
 
    | andor wrote:
    | The particulate sensor on my Xiaomi air purifier correlates
    | really well with the numbers from my city's air quality
    | network.
    | 
    | What doesn't work well for me is the auto mode, it barely
    | does anything at less than 50ug/m^3, way too high even for
    | the mediocre air in my area. So instead I use automation in
    | their app to let it run at full speed for 30 or 60 minutes.
 
      | 5e92cb50239222b wrote:
      | They use Chinese air quality standards, which are very high
      | relative to most other countries for (probably) obvious
      | reasons.
      | 
      | https://en.wikipedia.org/wiki/Ambient_air_quality_criteria
 
  | MengerSponge wrote:
  | If you live on a main road, there's likely a lot of pollution
  | in the air. How much is actually in your home will depend on a
  | lot of complicated things (prevailing winds, home construction,
  | etc), so it's best and easiest to just measure.
  | 
  | HN's own https://news.ycombinator.com/user?id=ahaucnx has a
  | company with a DIY version:
  | https://news.ycombinator.com/item?id=27124671
  | 
  | I got a Dylos before I learned about AirGradient, and I really
  | like it too. Depending on your budget and tech savviness, it's
  | a great option too.
  | 
  | One important note: these detectors don't do chemistry, and not
  | _everything_ that causes a spike of PM is actually a problem.
  | Showering, for example, will cause a spike for hours, but those
  | salts are probably fine. Running the oven will also cause a
  | spike, and those particles probably _aren 't_ fine.
 
  | [deleted]
 
  | throwaway290 wrote:
  | There is no level of pm2.5 that is considered safe to breathe,
  | and it is easy to find out levels in your area so make your own
  | call based on that.
  | 
  | It will be a placebo if your home cannot be isolated from
  | outside air or if you don't make an effort to keep windows
  | closed when air is bad.
  | 
  | Also, many expensive purifiers are overpriced junk compared to
  | even simple DIY solutions like those found on particlecounting
  | Tumblr and similar. Ideally the first thing to do is get some
  | reputable air quality monitors.
 
  | Mister_Snuggles wrote:
  | One of my cats, who's since passed away, was asthmatic. Air
  | purifiers throughout the house and a motion activated box fan
  | plus furnace filter near the litterboxes resulted in an
  | immediate and noticeable improvement in his quality of life.
  | I've noticed a similar improvement in my own health.
  | 
  | I've since ended up with a variety of air cleaners:
  | 
  | * IKEA FORNUFTIG[0] is a small and relatively quiet unit. It
  | can be wall-mounted, so it can take up virtually no space. The
  | unit is reasonably priced. Filters are cheap.
  | 
  | * IKEA STARKVIND[1] is a much larger unit (also available in
  | end table form[2] to save space), but also relatively quiet on
  | the lower speeds. It's an interesting unit - integrates into
  | Home Assistant (the unit speaks Zigbee), and has a PM2.5 air
  | quality sensor. This unit is a lot more expensive than the
  | FORNUFTIG, but the filters are reasonably priced.
  | 
  | * The box fan plus single furnace filter is incredibly noisy,
  | but really good at dealing with cat litter dust. There is a
  | huge range of price/quality when it comes to filters[, I just
  | use the cheaper ones since I'm focusing on large dust
  | particles.
  | 
  | * I have a couple of units that use Bionaire aer1 filters[3].
  | The units I have are quiet and reasonably sized, though they
  | get louder as the filter fills up. The filters are expensive,
  | and one of the units takes two of them which doesn't help
  | matters. There is a variety of filters available.
  | 
  | There's a huge spectrum of tradeoffs between noise, size of the
  | unit, filtration effectiveness, replacement filter cost, and
  | extra features. I'm not convinced I've found the sweet spot
  | yet.
  | 
  | [0] https://www.ikea.com/ca/en/p/foernuftig-air-purifier-
  | white-5...
  | 
  | [1] https://www.ikea.com/ca/en/p/starkvind-air-purifier-
  | black-40...
  | 
  | [2] https://www.ikea.com/ca/en/p/starkvind-table-with-air-
  | purifi...
  | 
  | [3] https://www.bionairecanada.com/en_CA/service-and-
  | support/aer...
 
  | phphphphp wrote:
  | I (in London) bought one recently (a COWAY Airmega) to try and
  | improve the air quality in my apartment, specifically, the dust
  | which has been reeking havoc on my breathing because of
  | allergies.
  | 
  | There is a noticeable improvement but it has not solved the
  | problem by any stretch: so while I don't regret the purchase,
  | and will keep using it, I am not how sure I'd recommend them
  | for the someone without breathing difficulties / allergies etc.
 
    | teaearlgraycold wrote:
    | I got the same one and it's amazing for California when the
    | air is smokey.
 
  | herbst wrote:
  | If you smoke indoors it's a must have I would say. It's a
  | difference between day and night.
 
  | fragmede wrote:
  | PM2.5 particles are considered harmful, ingest at your own
  | peril. Some air filters will also include an air monitoring
  | device, so you can just for yourself how many of those
  | particles are present (partially burnt food is an extremely
  | common source of these).
 
| stavros wrote:
| Is there something that works well for cat hair? I can't stand it
| everywhere, but I don't know if these filters will catch them. I
| tried to build a box fan filter, but it moved basically no air :(
 
  | Aerialoo wrote:
  | Use a bigger fan
 
| romseb wrote:
| > This will significantly decrease the waste footprint from a
| whole filter.. to just a sticker
| 
| I don't think I understand which problem this solves. I can turn
| on my Xiaomi Air Purifier with or without a filter. It's just a
| fan. Is this about a new version that does not work with an old
| filter?
 
  | GekkePrutser wrote:
  | Mine too, I have the 2S.
  | 
  | However I have read that the new air purifiers (from the 3
  | onwards) switch off after a couple of hours when they don't see
  | a filter sticker, or a used-up one.
 
  | pawelos wrote:
  | I have Air Purifier 3H, and with an old filter it displays big
  | red "0%" most of the time, instead of showing PM2.5 level.
  | Which is annoying.
  | 
  | And the filter works effectively a few times longer than what
  | is displayed (at least according to the PM2.5 sensors on the
  | same device).
 
| throwaway4good wrote:
| Nice hack. But my xiaomi air purifier works just fine with a non-
| xiaomi filter - only thing it will do extra is show a warning at
| power on.
 
  | GekkePrutser wrote:
  | True for the older models but the new ones switch off after a
  | certain time
 
    | throwaway4good wrote:
    | Mine is a 3H.
 
      | GekkePrutser wrote:
      | Oh ok, I heard some of them switch off for sure (after a
      | few hours). I read this on an online forum discussing
      | integration with Home Assistant, some users got around it
      | by just setting an automation in Home Assistant to switch
      | it back on again :) Which is what I would have done if my
      | 3S had had the same problem. But it doesn't.
      | 
      | Strange that some models are affected but others not.
 
        | throwaway4good wrote:
        | Maybe it is because I am in the EU? This stuff is
        | obviously in software and all my xiaomi gadgets get ota
        | updates regularly.
 
    | JohnJamesRambo wrote:
    | The air purifier people must have met some printer ink people
    | at a conference.
 
| VoidWhisperer wrote:
| I think my question with this would be:
| 
| How accurate is the filter durability that the normal filter <->
| air purifier tracks? If it tracks reasonably well (which, without
| more info, I have my doubts for the same reason printer ink
| cartridge capacity tracking is bad), wouldn't using these
| stickers kind of defeat the purpose of using the filter in the
| air purifier, since these kinds of filters do have finite
| durability and after that it isn't purifying the air as well as
| it could be.
 
  | GekkePrutser wrote:
  | I have one and it tracks very poorly. It tracks only the usage
  | time regardless of how fast the fan is running.
  | 
  | When on auto, it is mostly spinning at idle, hardly sucking air
  | through the filter, and as such it's hardly contaminating the
  | air filter (in fact the airflow is so low I stopped using auto
  | mode at all, there is just no point).
  | 
  | It also doesn't take into account how contaiminated the ambient
  | air is (even though it has an air quality sensor on the one I
  | have).
  | 
  | I run mine at about 40% so I use the filters about 2-3
  | lifetimes :) Even that is a pessimistic approach IMO because
  | the air here is very clean. I mainly have it because of
  | hayfever (pollen allergy).
 
    | chmars wrote:
    | In automatic mode, different ppm level should result in
    | higher fan speeds. That is at least the case with my filters.
    | Cooking for example can be a trigger.
    | 
    | You are of course right that automatic mode does not do much.
    | At the same time, higher fan speeds are noticeable (and
    | annoying).
 
      | GekkePrutser wrote:
      | For my environment it never ramps up in that mode at all.
      | Ambient levels are never higher than 10ppm or so.
      | 
      | I know the sensor works because once there was a small bin
      | fire outside. There was no visible smoke indoors, I only
      | noticed a slight smell. But the purifier immediately ramped
      | up and showed over 200ppm.. So it does work.
      | 
      | I'm surprised it's so low as I live at the 2nd floor on a
      | fairly busy street with many diesel buses passing.
 
  | chmars wrote:
  | The filter durability is time-based in my experience:
  | 
  | I set up several air purifiers at the same time in December
  | 2021 but used them in different areas, i.e., with different
  | filter loads. The air purifiers ran 24/7 and mostly in
  | automatic mode, except for some hours after known possible
  | coronavirus exposures.
  | 
  | Official end of filter life was reached after about five months
  | and for all filters on the same day. The air purifiers are
  | still running tough, that's a plus!
  | 
  | Xiaomi recommends to replace filters every 6 to 12 months. The
  | recommendation, however, is based on the use in polluted Asian
  | cities, I guess. We have rather clean air here. I therefore
  | assume that it is safe to use the filter for an additional few
  | months.
 
    | Danieru wrote:
    | HEPA filters get more effective overtime in exchange for more
    | restricted airflow. Thus the failure mode is "air is not
    | flowing" and not "air is not getting cleaned".
    | 
    | At home I use 3 air filters in various rooms. These are
    | standard/mid-range Japanese Sharp filters. Japanese because
    | we live in Japan, not because Japanese HEPA filters are
    | special. The filters themselves can be bought for about 30$
    | online. When the filters get near end of life I've had
    | success by switching to a higher fan speed. This is not
    | magic, at some point even on the highest setting airflow
    | starts to match the old medium speed. The high speed mode
    | consumes about 4x the electricity of medium speed.
    | 
    | The net result is there exists an intersection point where
    | continuing to use a filter costs more money than replacing.
    | For us in Japan with expensive electricity this point exists
    | sometime after the airflow has diminished but the filter is
    | viable on high speed. In cheap electricity countries the
    | filter might become unusable before electricity becomes a
    | significant cost.
 
      | 5e92cb50239222b wrote:
      | > because we live in Japan
      | 
      | May I ask why you're using them at all? Every time I look
      | at Japanese cities they seem to have PM2.5 levels in a
      | second-digit microgram range. A bad day seems to be
      | something like 15 ug.
 
        | bjoli wrote:
        | Poor ventilation and a stir fry on medium-high heat will
        | bring you above harmful levels for several hours in my
        | experience.
        | 
        | Candles, cleaning, frying. All very good ways to increase
        | air pollution in your home that nobody speaks about.
 
  | deno wrote:
  | In my unit it's just 365 days countdown.
  | 
  | OTOH a lot of the Xiaomi purifiers have built-in air quality
  | monitor so really you can just ignore the useless filter health
  | value and figure out if the filter is working for yourself,
  | based on how it performs.
 
  | userbinator wrote:
  | If they wanted to really track the filter life, they would use
  | a static pressure sensor like a lot of HVAC installations have.
  | It's clear what the companies doing this DRM shit are
  | prioritising, and it's not accuracy.
 
| qgin wrote:
| This is maybe the wrong place to post this, but with fire season
| approaching, a pretty decent high-volume air purifier can be made
| using filters, tape, and a box fan:
| 
| https://www.texairfilters.com/a-variation-on-the-box-fan-wit...
 
  | oppositelock wrote:
  | I used box fan filter setup to get through a couple of CA
  | wildfire seasons, but they're loud and take lots of room. I
  | used 4" filters in a triangle with the fan as the base. This
  | setup is far more effective than a single filter because it
  | makes the fan work better with some air space behind it.
  | 
  | These days, I have a BlueAir 211 in each room. It's the same
  | idea, just professionally made, it's not an eyesore, and it's
  | quiet. Going by my AQI meter, they're also more effective.
 
  | [deleted]
 
    | [deleted]
 
  | muxneo wrote:
  | Absolutely brilliant. Saved 100 to 300 bucks right there.
 
___________________________________________________________________
(page generated 2022-05-28 23:00 UTC)