5 ms·
Experiments on a $50 DIY air purifier you can make in 30s
- sp332 3y ago(2021)
- lamontcg 3y agoYou can do better with a Corsi–Rosenthal Box: https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box
- altairprime 3y agoThe gist of this post is that ‘better’ isn’t necessary; any will suffice. So long as there’s airflow traveling through the filter pleats, your air will get cleaned. If you’re in a wildfire scenario, you should — if you can afford to and can still find and purchase the parts — absolutely go the extra mile, because you need to maintain a filtration level sufficient to overcome the particulates brought in with outdoor air. Regardless, any time you have a box fan, just tying a filter to it will clean your air as effectively — but not as rapidly — as a commercial filter, under typical home scenarios.
- more_corn 3y agoThey are awesome and cheap but take up a lot of room.
- deleted 3y ago[deleted]
- mbishop 3y agoThey are indeed awesome and I made one with a simple box fan. It works great but it’s really loud. We can’t really have it on when company comes over. We got one of these instead and have been really happy with it. Pros: super-quiet low-energy computer fans. Uses standard air filters you can buy at Lowe’s. Cons more than a box fan. https://www.cleanairkits.com/products/brisk-box https://www.cleanairkits.com/products/brisk-box
- swozey 3y agoI have air purifiers and humidifiers in every room (I'm in horribly dry CO) and I still just live life sniffling and with a dripping scratchy throat no matter what I do. I take antihistamines, NAC (n-acetyl-..... cystine?) helps a lot, mucinex/gauff. I was hoping my big air purifiers would catch a lot more dog hair than they do. Have purifiers/humidifiers been a huge change for some of you? I can't prove that I wouldn't be worse right now without them. I love my huge humidifer it lasts about a week keeping a 10-20% humidity townhouse at 65%. But I think I'm expecting too much out of purifiers. Or have other respitory/sinus problems.
- thaumasiotes 3y ago> I have air purifiers and humidifiers in every room (I'm in horribly dry CO) and I still just live life sniffling and with a dripping scratchy throat no matter what I do. I take antihistamines, NAC (n-acetyl-..... cystine?) helps a lot, mucinex/gauff. I caught a cold seven years ago and there's been phlegm dripping into the back of my throat ever since. Medical opinions have been pretty uniformly "sucks to be you, huh? Now go away".
- lispisok 3y agoUltrasonic humidifiers (the ones that generate the fog) generate huge amounts of particulate matter to the point I'd argue they are a health hazard and shouldnt even be sold. If you have any ultrasonic humidifiers replace them with evaporative humidifiers. I actually discovered this independently when I used my air quality monitor to check the humidity in my house after buying a humidifier and saw PM was in the unhealthy range despite having my very large HEPA filter running in the same room. After some googling I discovered why. https://www.sciencedirect.com/science/article/pii/S0160412020318572 https://www.sciencedirect.com/science/article/pii/S016041202... https://www2.purpleair.com/blogs/blog-home/ultrasonic-humidifiers-a-source-of-pm2-5 https://www2.purpleair.com/blogs/blog-home/ultrasonic-humidi...
- s0rce 3y agoYou just need to use distilled/deionized water in ultrasonic humidifiers. You should not be using tap water as that creates hazardous particles, and you'll pretty soon notice dust over everything. They should come with more clear warnings regarding this issue as its severe and not everyone knows. Additionally the systems could have a simple conductivity sensor to stop running if the conductivity (ie. the TDS is too high).
- lispisok 3y agoI see articles pop up like this all the time on HN like it's some kind of revelation. All you need to remove particulate matter from your air is a fan that pushes air through an HEPA filter. You dont need wifi, bluetooth, lcd screens, or a phone app. All those things plus some fancy instagram marketing is tricking people to spend $700+ on an air filter.
- antisthenes 3y agoNone of these articles allude that you need any fancy tech to filter air. You're preaching to the choir. The people buying $700 air filters are typically not very tech or DIY inclined, although HN does tend to fall for "expensive is good" kind of marketing once in a while (most notably - Apple)
- conductr 3y agoAgree! However article is comparing to a $100 option and he spent about $60 on DIY supplies. The price differential is small enough that nobody should DIY. The convenience of having an auto-sensing device that turns on and off when based on changes to air quality is well worth the extra. As is the ultra low noise operation and added aesthetics.
- RangerScience 3y ago> nobody should DIY > nobody should DIY for price reasons FTFY. Lots of reasons to DIY other than price :)
- neogodless 3y ago
- yalue 3y agoOne thing the article doesn't seem to mention is noise. I've found that the "actual" air purifiers seem to be much quieter than box fans. Perhaps if you had greater control over the box fan's speed you could get the noise down to a comparable level, but I doubt the cheap type of fan used in the article is capable of such a thing.
- storyinmemo 3y agoIndeed, the thing that keeps me happy with the Coway 400 I've got is the very small power use when particulate is low and the automatic ramp up when it goes high. My fan I keep near my bed for my own comfort pulls 30 watts. The Coway pulls something more like 5 watts in low use. Expensive up front but low ongoing cost and 4 years running now.
- jerlam 3y agoYep, the DIY may work in an emergency but there are good reasons like noise, size, and power usage to get a commercial product if you're going to be living with it. The layout of the purifier is important in a crowded space - the DIY requires open space both in front and behind for good airflow, but the commercial ones have a front intake but vent straight upwards, so you can shove it against the wall. No one is going to put their air purifier in the middle of the room away from other furniture.
- StillBored 3y agoThe box fan's CFM is probably a good order of magnitude higher than most commercial purifiers, meaning in theory it should move more air through the filter, thereby cleaning the room faster. That said, it probably doesn't provide much vacuum/head, so the air that gets drawn through it probably doesn't change much with tape, although I'm guessing the energy draw goes down... So two comments for DIY air filters, put fiberglass or similar prefilter over the hepa filters, and/or add more filters instead of tape around the fan. Even if they aren't hepa they will catch stuff.
- cheald 3y agoThe primary perk for a more expensive unit is the ability to modulate that fan speed based on the particulate level in the room, IMO. I've got a couple of units that I paid ~$140 for which can step their fan speed up and down based on the measured air particulates. Most of the time, they're running at low speed and are effectively silent - just cycling the already-pretty-clean air in the room at a low rate - but if something causes a spike in particulates (say, cooking), they'll crank up to a significantly higher speed (and level of noise) until the air is cleared. If you've got a box fan running all the time anyhow and don't mind the noise, though, strapping a HEPA filter to it makes plenty of sense.
- klipklop 3y agoSadly the state of California bans simple box fans + filters from being sold. For example if you try to buy a "Lasko Air Flex Steel Portable Home Office 3 Speed Air Purifier Machine Box Room Fan with Manual Ergonomic Control Knob and 6 Foot Cord, White" from Amazon you will be greeted with this when you try to order: """This product does not meet California air cleaner regulation requirements, and cannot be shipped to California""" This is essentially like the video, but a slightly beefed up box fan to handle the extra load from the filter. It also takes standard household furnace filters. People have tested these and they totally work. For a state that often has horrific air quality due to wild fires it's total BS you can't quicky order something like this off Amazon in a pinch.
- teeray 3y agoIt looks like there’s an opening for someone to market one of these as a scientific instrument for the outdoor collection of airborne pollutants.
- mustacheemperor 3y agoThere is also an opening for someone to market this exact product exactly the same, but just undertake the testing to prove it actually works as advertised to comply with California law. As a state where air quality is a major public health concern, it seems very reasonable for the regulations to protect consumers from being sold scam products that do not actually filter the air. I understand this concept is well tested and proven, but I think we're all familiar with the general counterfeit product issues on Amazon and I would be 0% surprised to get a fake of even such a simple design.
- ethanwillis 3y agoIt would be more reasonable for the government to protect its citizens in a state where air quality is a major public health concern.
- SECProto 3y agoReading [1] about the regulations, it sounds like the only requirement (for self contained air cleaners) is that it has to be certified, and can't produce ozone. That seems pretty painless, and I would like the comfort of knowing that if I buy an air cleaner, it actually does what it says. Same as masks should have testing requirements to show efficacy. [1] https://ww2.arb.ca.gov/our-work/programs/air-cleaners-ozone-products/air-cleaner-regulation-ab-2276 https://ww2.arb.ca.gov/our-work/programs/air-cleaners-ozone-...
- randa222 3y agoThis experiment could use an additional negative control: Fan with no filter. There are many possible explanations for the observed data, for example, the air movement through the fan changes the static charge of the smoke particles, causing them to cling to objects in the room. Or, the smoke particles could be binding the plastic blades of the fan. Or, distributing the smoke throughout the room dilutes the smoke concentration at the sensor. For fun, ask your TA for the full list of possible hypotheses! At this point, we can't say that the HEPA filters are causal. The tape versus no tape experiment produced unexplained and surprising results, which is even more reason to run careful negative controls. Now, if we could easily label the smoke particles, e.g., using a fluorophore, and measure their distribution after filtering, we'd know exactly where they're going.
- Sporktacular 3y agoAnother homemade air purifier post from dynamite. Last update 2021. Posted to HN here: https://news.ycombinator.com/item?id=28394752 https://news.ycombinator.com/item?id=28394752
- _neil 3y agoI have a setup like this in my office (but with a larger filter and gaffers tape for the edges). It isn’t smart and it’s loud. I’ve mitigated that slightly by putting it on a wifi plug and running it full blast when I vacuum or when I leave my office for snacks. Seems to work well enough.
- Sporktacular 3y agoRepeat post