Reverse engineering Xiaomi air purifier NFC stickers
flamingo-tech.nl
flamingo-tech.nl
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.
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/
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.
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.).
Something like this:
(This is less possible on things like printers, which have to synthesize somewhat complicated motion, carefully release ink at the right time, etc.)
It’s a very simple concept hidden behind a lot of unnecessary technology.
Strange that some models are affected but others not.
The forum where I read this was also EU based though. Weird.
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.
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).
You are of course right that automatic mode does not do much. At the same time, higher fan speeds are noticeable (and annoying).
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.
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.
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.
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 µg.
Candles, cleaning, frying. All very good ways to increase air pollution in your home that nobody speaks about.
Unique to Japan is the pollen. After WW2 Japan was reforested in mass with a single variety of tree. Thus making the exact pollen release an annual torture test for anyone without air filters. My theory is everyone eventually gets pollen alergies, it's just a matter of time. My wife is affected during pollen season, and I've starting to notice myself become affected as well.
We do not stir fry, that's not a thing in Japanese cuisine. And our cooking is all IH so no gas particle. Yet even we will notice if the air purifiers are not running. We'll first notice our noises are a bit stuffy, and omly then check to find a kid has turned off the air purifier.
An upshot to low pollution is filters last ages.
Xiaomi filter processing Canadian air in a semi high traffic area after 2 years looks better than my Asian country filter after 6 months.
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.
Coway and Winex both do not do this and make top-rated units.
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?
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.
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).
Enabling the user to do what?
I feel like a 100% used filter will still do a pretty good job, so unclear how much of the utilization % has commercial reasoning?
Not to suggest that what the manufacture decides “100%” is is actually that.
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.
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.
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.
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.
For most household tasks, a 12-volt drill is more than adequate. It’s the smallest
class of drill, and due to advances in battery and motor technology, such models
have become formidable with regards to power. … If you’re a rabid DIYer with plans
to build a deck, a doghouse, and a tree house, we recommend a stronger, 18- or 20-
volt drill.
WC did cover the popular "pro" brands available in America (Milwaukee, DeWalt, Ridgid). Potentially they should've included Makita but Festool and Hilti are way beyond the price point of the home gamer target audience. Hilti especially goes after the fleet market, so even if you're a pro they're not necessarily going to be your goto brand unless you're at a larger company. Anecdotally Milwaukee kit seems to be very popular amongst tradesmen out here. But like with circular saws there's probably some regional variation.
I think WC did miss some important stuff for home gamers and they definitely got it wrong with the Bosch drill. It's small. It's tiny. It's about as long as the DeWalt and about an inch and a half shorter in height. You don't buy it for the power you buy it for the size. If you need to stand it up on the battery, get a bigger one with a foot.
https://www.nytimes.com/wirecutter/reviews/the-best-drill-fo...
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.
The air here is already really good (~10 reading) most of the time so I reckon I can run my filters much longer than Xiaomi thinks is appropriate.
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.
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.
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.
I guessing that the benefits are less certain in more typical cases.
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.
And healthy is something like <100
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.
It really depends on where you're coming from.
I have one of those air purifiers from Ikea (Förnuftig). 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.
What doesn't work well for me is the auto mode, it barely does anything at less than 50µg/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.
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.
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.
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.
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.
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.
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.
-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.
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.
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.
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.
I've since ended up with a variety of air cleaners:
* IKEA FÖRNUFTIG[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 FÖRNUFTIG, 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...
https://www.texairfilters.com/a-variation-on-the-box-fan-wit...
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.
I've had more than one instant of airfilter going wild reminding me I had forgotten a cooking plate on