Web designers: you need a Retina MacBook Pro - <AUTHOR> http://www.marco.org/2012/07/05/web-designers-need-retina <comment><USER2> _I've been using a Retina MacBook Pro for one week, only as a secondary computer,2 and I've already changed my font, redesigned my narrow layout's header, and conditionally replaced an image with text. I've noticed that fonts, especially, respond extremely differently on the Retina screen: many of my old, non-Retina choices simply didn't look good, and many fonts and metrics that were previously poor for screen use can be used nicely on Retina screens._

So you swapped out your old fonts that look good for 99% of people for fancy new ones that, while "poor for screen use" for those 99%, look nice on Retina screens?

</comment><comment><USER3> > Windows-using web designers, if such people still exist: I'm sure there's > something you can do to enable high-DPI mode on Windows

Is the snark really necessary here? Why so mean?

<comment><USER4> > Is the snark really necessary here? Why so mean?

Marco has long shown a visceral disdain for non-Apple products and those who use them. Unfortunately, this sort of behavior is on the rise in general, and not many people are willing to call out those who find it necessary to take a potshot at the "other camp" every chance they get.

As for Marco's comment about Windows-using web devs, one of the most respected members of our community and a serial web entrepreneur, patio11, appears to be a Windows user, at least as of 6 months ago: <http://hackerne.ws/item?id=3422608>

<comment><USER5> The comment was about web designers not developers. Patrick is well respected round these parts for good reason, but it is certainly not for his design skills.

I didn't read it as being particularly harsh or snarky. It seems Web designers using Windows are becoming a rare breed. At least from what I can tell anyway. FWIW, I am not a designer and run Mac/Windows for testing purposes only.

</comment></comment></comment><comment><USER6> This is just silly. Are there legions of websites that work on non-Retina computers that actually break on the Retina MacBook Pro (rather than just looking bad)?

Web designers should not default to the latest-and-greatest. When they do, they often produce sites that are completely unusable without it. Web designers should spend more time worrying about users that don't have the latest-and-greatest (aka most users).

Most web designers need old laptops and low-end smartphones far, far more than they need a Retina MacBook Pro.

<comment><USER7> Certainly not legions but it is worthwhile to step into an Apple store and give your sites a try. I was surprised to find my canvas-based code breaking on the Retina MacBook Pro.

FWIW, the cause was getImageData(0, 0, w, h) returning 4 _w_ h pixels and not w*h as I naively expected.

</comment></comment><comment><USER8> This article is ridiculous. The author essentially suggests that we pander to his demographic (see footnote 1, "Windows-using web designers, if such people still exist") for a non-existent reason, namely, that "you may not realize quite how bad it looks when any graphical assets show at 1X.". This is the type of irresponsible FUD that I would not expect to find here. Show me a website that looks worse on a Retina display, and I'll show you a crappy rendering system.

<comment><USER9> But retina display is the future. (At least I hope so.)

<comment><USER8> It may be, but no website I've looked at on the iPad 2 looks better or worse than it already looks like on a non-retina desktop/laptop.

EDIT: Gah, I meant the iPad 3. Slip of the finger or slip of the mind, make of it what you will.

<comment><USER10> Clearly this is the truth. Except (and I'm being quite serious here) to those who just dropped a big chunk of self image into their new toy. There's a huge psychological investment to a product like this. It's _better_! And anything that prevents it from being/seeming/acting better is an abomination. Marco Arment is deeply, personally offended that site designers aren't improving their work so that it looks better on his personal screen, because that situation reduces the value of the thing he so admires.

</comment></comment></comment></comment><comment><USER11> > No respectable developer would ever ship an app that wasn't extensively > tested on real devices.

I find this offensive. You are knowingly mixing facts up to support your argument.

Testing on a real device is entirely different thing than testing on a real device with Retina.

Your whole article is about testing on Retina devices, and suddenly an argument about something completely different. (Testing on real devices.)

What's up, do you think your readers are stupid?

</comment><comment><USER12> Ok, so the truth is raising the hackles of HN. Cool. Examine why you're upset, is he wrong or is it because he's right but he's talking about the other team/company that you don't like?

He is right to say that web designers need to start designing for high-dpi displays because high-dpi is going to be or already is the norm. Look at phones, they have what 150-200+ dpi? Tablets? Yep, high-dpi there too.

Windows? Well, actually yes. Windows 8 was designed to support high-dpi as well. [http://blogs.msdn.com/b/b8/archive/2012/03/21/scaling-to- dif...](http://blogs.msdn.com/b/b8/archive/2012/03/21/scaling-to-different- screens.aspx)

Perhaps the article would be better worded to say that web designers should buy Retna MBP because high-dpi is the future and Mac, Windows, iOS, and Android are all going to have high-dpi screens inside of a year or two, so it's going to take off pretty fast, and the Retna MBP is the best/only mainstream high-dpi workstation you can buy right now.

Of course, that would be rational and nuanced and those things don't get you clicks, links, or pageviews because after all this is the internet.

<comment><USER13> Windows has been scaling to various DPIs for ages (sometimes to undesired out- of-the-box resulsts, such when, a few years ago, I plugged in an XP desktop to an HDTV over HDMI and it tried to make the fonts display at the same physical size as on a monitor despite me sitting much further away). It's something it (and Linux, and Android) has ahead on the curve of compared to Apple—from an engineer's perspective, just going with doubling is a rather inelegant solution.

XP wasn't very good at it when it came to third-party apps, but on Vista or 7 (I forget which I was on back then now) once I got the DPI slider in the right place for that TV, it provided a quite enjoyable experience, even on older or non-standard apps.

</comment></comment><comment><USER14> It is important but not urgent (sorta depends on your site demographics). I'm not dropping a couple grand for a 1st run, rushed to market laptop. I can test now using the other methods he mentioned and I'll get a retina laptop when they are more reasonably priced, the hardware is more refined, and when most software is updated to look right.

</comment><comment><USER15> There are a number reasons to adopt retina graphics for your website today but it's not for everyone.

Consider the time it takes to update and maintain 2 versions of all images and ask yourself, is the >1% user base going to outweigh the time it takes to update this?

Make sure you consider the possibility that the >1% who are early adopters of the retina macbook may also be the type of early adopters who would try your alpha version.

As a designer, I know it's a major problem that if you primarily work on the best/brightest displays, you forget what your designs look like everywhere else.

So if you decide to "go retina", make sure you don't get carried away with fine lines and make the <99% squint to see your 8px #f0f0f0 text.

</comment><comment><USER16> Between the Mac, Cinema Display, iPad, iPhone/Touch and now a Retina Display/Mac -- being a web designer is pretty hard on the wallet these days me thinks.

And that's just Apple.

<comment><USER17> Perhaps akin to my thought: 'So, I need to spend $2500 on another laptop because I have no source for an equivalently featured monitor that I can plug in to what I have.'

Monopolies... [de facto, if nothing else]

</comment></comment><comment><USER18> Apple had a WWDC 2012 session on optimizing web sites for high DPI displays. Interesting but not terribly complex stuff. I think if you follow the best practices they outline you can feel pretty confident your site will look good on a high DPI display. If you have a high enough resolution display you could always switch to high DPI for testing.

</comment><comment><USER19> If the thing would ship. I ordered this thing weeks ago, and the Apple store ever since then has said "ships in 3-4 weeks." Every week I go to check on my order for the retina MBP and it says this.

They either really dropped the ball on manufacturing this laptop or it's the best selling Mac ever, because they just cannot ship any.

</comment><comment><USER20> I'm really excited for the high DPI Web. Higher resolution should be the last piece of the puzzle needed to finally kill the (terrible) practice of using images or Flash or (gulp) Silverlight to display text. Finally text can be beautiful to graphic designers, but still be text to developers and software.

</comment><comment><USER13> There is probably a simple explanation, but I'm stuck wondering why a pixel- doubled image looks worse than that same image at native resolution on a lower resolution screen? Why doesn't "combining" four pixels into one make it look the same?

</comment><comment><USER21> I bought one as my primary work machine for developing iPhone, iPad and Android apps and I can recommend it to any developer of all sorts. This is just a really nice developer machine, I love coding on that thing.</comment>


Sun Pranks From the Past - <AUTHOR> http://www.sun.com/aboutsun/media/presskits/25years/sunpranks.html <comment><USER2> They get a lot less outrageous as time goes on. The 2005 one is pretty sad in comparison to the "Ferrari in the pond."

</comment><comment><USER3> I almost was expecting the release of Java to feature in the list.

</comment><comment><USER4> I thought this year's was funny albeit nowhere near the scale of past pranks.

<http://blogs.sun.com/jonathan/entry/the_video>

</comment><comment><USER5> "And then the bubble burst"</comment>


Are free trials the answer? - <AUTHOR> http://alexblom.com/blog/2010/05/are-free-trials-the-answer/

<comment><USER2> I don't think that question can be considered outside of a specific product. Freemium makes sense in professional apps. As it promotes lock in right from the start. As an example consider 3d art apps. Maya and Houdini have freemium versions where the free version might as well have no limits for the beginner. So when you are starting out you learn the houdini work flow and way of thinking about things and there is a bit of lock in. Modo, silo both do 30 day trials that isn't enough time for me to learn how their software works let alone learn how to model, so they must be hoping for converts not new customers.

</comment><comment><USER3> Depends on the question.</comment>


Graphene breakthrough may yield contact lenses with night vision - <AUTHOR> http://www.independent.co.uk/life-style/gadgets-and-tech/contact-lenses-with-night-vision-could-be-on-the-way-thanks-to-graphene-breakthrough-9208212.html

<comment><AUTHOR> Current night vision technology needs bulky cooling equipment to stop the detectors getting confused by their own heat radiation, but the graphene-based models can do the same job using just a few layers of the atom-thick material.</comment>


Show HN: Brainfuck with threads and assertions - <AUTHOR> https://github.com/scotchfield/brainfuck_py

<comment><USER2> I made GUI for brainfuck, by 'including' libraries you can modify specific memory addresses to change pixels on a buffer. Something like a system call.

[http://enginmercan.com/?p=32](http://enginmercan.com/?p=32)

It is in Turkish, just hit run and you should be able to see a hello world.

@gui@ includes the library (for my JS brainfuck interpreter) which adds a canvas to my page, BF code writes into it

<comment><USER3> I've also written a visual BF interpreter[0], where you can watch memory and the instruction pointer as the program runs. (I think it's still broken for input though perhaps.) Pretty cool image buffer setup in yours though :)

[0]: [https://github.com/lfowles/brainporn](https://github.com/lfowles/brainporn)

</comment></comment><comment><USER4> I guess being able to code brainfuck is like understanding special relativity. You think it will impress the opposite sex, but it wont, unless you're a girl. :P

But it does however give you a better understanding on how things work.

<comment><USER5> Protip: General Relativity is harder than special relativity

</comment></comment><comment><USER6> I expect the next version of Brainfuck to have unit tests and agile scrum sprints.

</comment><comment><USER7> In case someone else also doesn't know what Brainfuck is: [http://en.wikipedia.org/wiki/Brainfuck](http://en.wikipedia.org/wiki/Brainfuck)

<comment><USER8> And for a "practical" example: [http://www.99-bottles-of-beer.net/language- brainfuck-2542.ht...](http://www.99-bottles-of-beer.net/language- brainfuck-2542.html)

Cheers.</comment></comment>


Majority of women who have an abortion don't regret it five years on - sahin-boydas https://www.newscientist.com/article/2229842-majority-of-women-who-have-an-abortion-dont-regret-it-five-years-on/ <comment><AUTHOR> > five years later 99 per cent said [having an abortion] had been the right > [decision].

> five years on, 84 per cent of the women said they either had mainly positive > emotions or no emotions about the procedure.

> The findings could have been biased by the fact that only 38 per cent of > those asked to take part in the survey accepted, and women who felt more > negatively about their decision might have been less likely to participate.</comment>


Ask HN: What do you think of mobile crypto mining? - <AUTHOR> Hey folks!
Before y'all pitchfork me, I am just curious with this aspect of mining. Let's say if Twitter suddenly decides to add a blockchain stack to their mobile app. You will get paid to provide processing power using a proof of stake (PoS) algorithm. I mean these social networks have millions of users, wouldn't it be great if they pay for usage?
Those are some of my dumb thoughts, but I have seen people have great thoughts that they could share here.
Best Regards,
Steve <comment><USER2> The problem is most of us are already limited in what we can do on our devices by battery life and mining will serve only to drastically shorten the runtime of your device

Also PoS is not generally mined or if it is it will have a PoW phase to mine the coins until all are created and it then becomes PoS

<comment><AUTHOR> Any thoughts on tech implementation that you might think could be feasible?

<comment><USER2> for mining i dont really think so unless you happen to have a large number of spare devices that you can use which are constantly plugged in. mining is pretty much always going to be a very resource intensive process so its going to eat your battery in most cases.

There may be another system which could be possible but i havent looked into other solutions much, i know there is Xtrabytes proof of signature system which may be a good fit for mobile

[https://blog.xtrabytes.global/technology/proof-of- signature-...](https://blog.xtrabytes.global/technology/proof-of-signature- triumphs/)

</comment></comment></comment><comment><AUTHOR> If you need a reference, you can take a look at Electroneum: [https://electroneum.com/](https://electroneum.com/)</comment>


How to have a better death - <AUTHOR> http://www.economist.com/news/leaders/21721371-death-inevitable-bad-death-not-how-have-better-death <comment><USER2> Uncomfortable topic that needs talked about more, far too many have long painful ends needlessly.</comment>


I made a browser-based chat app. Based on node.js and nodechat. - <AUTHOR> http://twich.me/hackernews

<comment><USER2> That was fantastic and fast, but it definitely needs Flood control <http://www.irchelp.org/irchelp/mirc/flood.html> and <http://en.wikipedia.org/wiki/Internet_Relay_Chat_flood>

<comment><AUTHOR> Definitely needs flood control. Thanks for the ref. I'll read up on it.

</comment></comment><comment><USER3> I got a series of "lol" popup dialogs, then was pushed out of the room and returned to Hacker News. I was fairly frightened by this turn of events and won't return using my normal browser without some assurances that I'm not going to be victimized. I guess I'll fire up a virgin firefox profile and try some more.

On the user interface side, it would make sense if any line starting with "/" was interpreted as a command (legit or not). Otherwise, you'll have a lot of "/help" and so forth in the channels. Especially since "/print" _is_ a valid command.

Update: Not sure, but I think someone has now injected some JS which causes everyone else in the channel to continuously spam it with the word "crash". Good times...

</comment><comment><USER4> wow too bad it tanked so quickly with spammer types

very cool and thought provoking. BTW, I was "foo". :)

Feature request: When I log out & come back to a room, the conversation should still be there.

edit: interesting, someone just downvoted a bunch of comments here. HN has grown large and attractive to idjits. I upvoted the zeros back to ones.

<comment><AUTHOR> Re: spam Well I was half expecting it. I suppose now we sorta know how it holds up to heavyish traffic, even if it's spam...

Thing is twich rooms don't hold any history. it works more like throwaway chatrooms atm.

Persistent rooms - I'm strongly considering implementing down the road.

</comment></comment><comment><AUTHOR> You can spawn your own twich room by just linking to

<http://twich.me/any_room_name> or <http://2wi.ch/any_room_name>

Works on iOS and Android too.

Comments and feedback appreciated.

<comment><USER5> looks great, can I control who is in my room if I make one?

<comment><USER6> This should definitely be a feature. Also, when somebody posts it scrolls down to the bottom. Sometimes the bottom half of the window showing the chat turns black and blocks out the text in opera on mac.

</comment></comment></comment><comment><USER7> Bug (or feature I guess): if I scroll up and someone posts, it autoscrolls me down to the page.

<comment><USER8> Annoys me too. But overall, a nice thingy.

<comment><AUTHOR> Agreed, the User Experience definitely needs a lot more work. Thanks for feedback.

</comment></comment></comment><comment><USER9> If someone types an extended string of unbroken characters, you should break that string for them. If you don't, the horizontal autoscroll bar appears and actually blocks the 1 most recent comment.

</comment><comment><USER10> Unless you've fixed a XSS bug in the hour since it was posted here, kudos on being the first Node.js chat site I've seen like this that was not vulnerable to XSS discoverable within ten seconds.

<comment><USER11> The actual app is pretty well xss proofed.

But, unfortunately if you go to this link...

        http://twich.me/<script>alert(document.cookie);</script>

(had to stick it in code block because HN auto marks it as spam)

<comment><USER10> Ah, alas, I stand corrected. That's a 10-second one. I didn't do much more than a 10-second pass, that's usually sufficient.

<comment><USER11> Unfortunately there was also another one in the youtube embedding feature, took half an hour to find :)

</comment></comment></comment></comment><comment><USER12> Open sourced code or it didn't happen.

<comment><USER13> bump

</comment></comment><comment><USER14> How's it different from <http://github.com/ry/node_chat>?

Here's my clone with a shared jukebox: <http://github.com/akkartik/node_chat>

<comment><USER15> infinte rooms. so you just go to twitch.me/foobar and send other people that link. You're chatting with just those people.

Sure, you could host node_chat yourself, but a) then you have to host node_chat yourself, and b) if you found yourself in a situation where you wanted 2 rooms open at once, you'd have to start up another instance of node_chat.

<comment><USER14> Ah.

</comment></comment></comment><comment><USER16> Great work, was fun till the spammers showed up.

You leaning towards open sourcing it or selling access to chat servers?

<comment><AUTHOR> Thanks. Yeah I'll definitely have to work on the spamming. Leaning towards open sourcing it and maybe run a hosted service.

</comment></comment><comment> mike-cardwell Beautiful.

However, your restrictions on names are too strict. I should be able to use the name 話筒. Nice that I can use chinese characters in the chat room name though.

Do you have any intention to monetise this? If so, do you have any ideas you'd be willing to share?

</comment><comment> mike-cardwell Also, do you intend on making it possible to use without javascript enabled? An iframe for the chat input and one for the output each doing long polls with meta refreshes should do it. Considerably less efficient of course, but opens the app to more users...

</comment><comment><USER17> Can't read the dark grey on black.

</comment><comment><AUTHOR> hi everyone. suggestion: start your own twich by just linking to <http://twich.me/[roomname]>

and post the link to get others chatting with you. it's getting too crowded in the main room.

</comment><comment><USER18> Interesting because injecting script tags shows them properly escaped but also seems to be evaluating them. Not sure how both can happen at the same time.

</comment><comment><USER19> here's another long polling chat, in Python and with source code: <http://chat.gevent.org>

</comment><comment><USER20> Really out of subject; but those colors are pretty cool. I wish I had a theme like that for Textmate or IRC.

<comment><AUTHOR> Color scheme is homage to original nodechat demo which uses the same. <http://chat.nodejs.org/>

</comment></comment><comment><USER21> Love it, I'm at <http://twich.me/chegra>

</comment><comment><USER22> I love the embedded YouTube :)

</comment><comment><USER23> I think I would be more impressed if this used WebSockets or something. How many Node chat apps have we seen? .. Actually, how many AJAX chat apps have we seen? I'd like to see a different network project, or at least one that uses sockets instead of AJAX polling ..

<comment><USER24> Would you like a pony too?

How about you build one?

</comment></comment><comment><USER25> Still vulnerable to XSS...

</comment><comment><USER26> for (i=0;i<=500;i++) { $('input#entry').val('kjhjkh' + i); $('input#entry- btn').click(); } or you could just push it to the url

heaps of people have injected js too

<comment><USER27> while(1){ $('input#entry').val('hahaha'); $('input#entry-btn').click();}

</comment></comment><comment><AUTHOR> hmm... someone's stress testing <http://2wi.ch/hackernews> atm. let's adjourn someplace else. suggestions?

<comment><USER11> Slight bug: you can pass in %31 as your nick which makes it '1' bypassing the 3char limit.

<comment><AUTHOR> Thanks for picking that up. I would've never picked it.

<comment><USER28> you need to re-evaluate how you are handling characters. you aren't escaping and encoding properly. there is no point in just smashing the little bugs that people bring up because it will still leave other things open. time to re- eval.

<comment><USER29> > _"you aren't escaping properly ... re-eval"_

      eval(eval(escape(string)))  ?

</comment></comment></comment></comment></comment><comment><USER30> Love the BitchX inspired theme :)

</comment><comment><USER31> I love this one!!! I can start the group chat in a second!!!</comment>


Build a do-it-yourself home air purifier for about $25 - <AUTHOR> https://www.uofmhealth.org/news/sinus-hepa-0630 <comment><USER2> I built my own air purifier in 2016, living in London, I was living in a basement and was having breathing problems due to mould. My landlady was gaslighting me at the time, so I built the air purifier. It worked for a while but mould spores cling to the paper filter and eventually grow into the filter material. I think Dyson uses glass fiber filter to stop this problem. My filter helped a lot, but eventually I had sclerosis infection on my brain and ended up in hospital with lung infection and brain lesion, still recovering after two years, and I will never be my old self again. I was subletting so had no grounds for complaint, I had to choose between homelessness or phoning a distant relative I hadn't spoken to for 24years, I chose the latter and I think it's the reason I'm still here.

<comment><USER3> Woah, this is pretty scary. Thank you for sharing. How did you know it was mold that was in the air? Is there some sort of test kit that you can buy to test for this. Mold is pretty hard to detect because you can't really see it because it typically hides between the walls.

Any advice appreciated.

<comment><USER4> The CDC has some recommendations on it (yes you can have mold tested to see if it's dangerous):

[https://www.cdc.gov/mold/stachy.htm](https://www.cdc.gov/mold/stachy.htm)

I'm not really sure about keeping the humidity below 50% though. The UK and most of Northern Europe has rather high humidity in the winter. It commonly reaches 80-90 RH outside, so you'd have to heat your house to 25c/77F to bring the humidity below 50%.

<comment><USER5> "The UK and most of Northern Europe has rather high humidity in the winter."

Indoors? No, not at all. In the winter the temperature in my house/office is 21-22C and 17 at the lowest at night, and I have to run a _humidifier_ 24/7 to keep the humidity over 30% (otherwise the wooding floors shrink too much).

<comment><USER6> (anecdata but...)

Currently in the bedroom (thanks Netatmo) it's 17.8° and 69% humidity (with one of the three windows open about 0.5"). That compares to 14.0° and 78% on the balcony. Looking at the graphs, 50% is the lowest indoor humidity over the last month.

<comment><USER5> Yes, bedrooms have the windows open more often, and usually less/no heating. How many hours a day do you have the windows open? Is there a heating source on or nearby? If you close the window, you'll see RH drop quite fast (in most houses). I'm going to try this same experiment tomorrow, I'm quite interested to know.

Still - mold in houses is not a problem in houses in Western/Northern Europe, except for the most pathological cases (for example, mold scores you iirc 2 points in Belgium on the 'uninhabitable property' test, where 9 gets your building declared unfit for living in. Having small holes in the roof or small cracks in the walls (still structural defects) gets you 3. That's how unusual mold is around here. OTOH when I lived in New Zealand, mold was met with 'eh, there's bleach in isle 5 at Countdown, just wipe it down.'. I was like 'wut?'.

<comment><USER6> > If you close the window, you'll see RH drop quite fast (in most houses).

Alas, it does not, but that's possibly because other windows are open around the place and there's relatively good airflow.

> I'm going to try this same experiment tomorrow, I'm quite interested to > know.

I'll see how it goes tomorrow with the window closed and various doors closed to minimise the effect of the other windows.

</comment></comment></comment></comment></comment></comment></comment><comment><USER7> Important tip: if you set up an air purifier in your home, make sure to plug all drafts around your house: windows, doors, etc. Even a DIY purifier with small airflow can make your indoor air excellent if given enough time to do so and no leaks to fight against.

If you want to get some fresh air in your home, do not leave a window half- open all day long—instead, open all your windows at once to cycle the air as fast as possible, then close them again and let the purifier do its job. If you do that in the morning (ideally just before leaving, if you aren't staying home), you'll have great air quality through the entire evening and night.

Since we're on HN, I'll also mention a toy project I built a while back [0]. It uses a Raspberry Pi to read particulate matter sensor mesurements over serial link from a Dylos 1100 Pro, then pipes it into Redis and InfluxDB and ultimately Grafana for presentation. I've used it to track the air quality in my home in for the past year or so and it's pretty fun. In my case, cooking is usually the biggest contributor to poor indoor air quality!

[0] [https://github.com/peferron/air-quality](https://github.com/peferron/air- quality)

<comment><USER8> Very interesting!

How does the Dylos 1100 Pro compare to, for example, the Nova SDS011 sensor? By my cursory review, the SDS011 is much cheaper and appears to offer a more native Raspberry Pi-compatibility experience.

Is the Dylos more precise? Can it produce readings the SDS011 can't? Are the two sensors measuring fundamentally different things?

Finally, if you had to do it all over again, would you choose a different sensor or stick with the Dylos?

Thanks for sharing your project and for your insights!

<comment><USER9> SDS011 is the basis for luftdaten.info; have a look here for a diy guide (optionally including humidity/temperature as well): [https://luftdaten.info/en/construction- manual/](https://luftdaten.info/en/construction-manual/)

<comment><USER10> Hi, this is an interesting project. It seems to be targeted for outdoor measurements. Do you know if this also suitable for indoor measurements (meaning if you want something for indoor air quality, would you measure the same things?)

I recently watched a video from dhh ([https://youtu.be/MRqh8oLY7Ik](https://youtu.be/MRqh8oLY7Ik)) about air quality at home and was thinking if there was a nice diy solution for measuring it.

</comment></comment></comment></comment><comment><USER11> Generally there are two classes of objects that you want to filter for.

Particulates and VOC (Volatile Organic Compounds). Think of particulates as specs of dust with varying size and VOC's as random chemical compounds such as spray paint, smoke, oders.

The general go-to clean room/industrial filter stack is Prefilter(F5 Bag)->HEPA->Activated Carbon. The pre-filter catches all the big particulates to prevents clogging the HEPA filter. The HEPA filter catches all of the really small particulates. The activated carbon captures most of the VOC's/oder/smoke.

The official way to monitor when a particulate filter is bad, is to measure the pressure drop across the filter, and compare to manufacture specs. For the carbon filters, you would install a gas sensor measuring whatever chemical your trying to scrub. When there is a spike in that particular gas compound from your sensor. You know the carbon filter is saturated, and should be changed.

It looks like the the filter mentioned in the article video,combines all the filter products into a single product. Nice! If your air handler can manage the increased pressure drops, please buy the most legit filters you can buy. It's literally the cheapest insurance you can buy.

<comment><USER12> > "The general go-to clean room/industrial filter stack is Prefilter(F5 > Bag)->HEPA->Activated Carbon."

yup, i bought a blueair 211+ ([https://www.blueair.com/us/blue/blue- pure-211/1695.html](https://www.blueair.com/us/blue/blue-pure-211/1695.html)), that has exactly those filter elements in a nice (if bigger than expected) package. this model was recommended by both consumer reports and the wirecutter (until recently, cynically thinking they didn't pay wirecutter's "endorsement fees"). it's effectively eliminated my constant coughing, sneezing and runny noses before i got it.

<comment><USER13> I just bought the same model. What makes it so effective is that it has a filter on four large sides so it can process a large volume of air very quickly.

<comment><USER14> Does it spew out ozone? My memory may be off but I remember this model not meeting CA air purifier standards which was why Amazon couldn't ship it to me

<comment><USER12> no, there is no ozone generator in this model (usually that's done using electrostatic plates).

<comment><USER14> I'm still curious then as to why this specific unit doesn't meet California air purifier standards, which is why Amazon won't sell it to me.

<comment><USER12> i'm not sure. i live in california and bought mine on amazon. wish i could be more helpful!

</comment></comment></comment></comment></comment></comment></comment><comment><USER15> Huh! I independently "invented" this myself a couple of days ago when the Camp Fire blanketed the bay area in smoke. I got a 20x20 filter and some duct tape from Home Depot and a box fan from Target. (After discovering that Home Depot only sells fans in the summer.)

I don't think I was the only one, though. HD was doing a brisk trade in 20x20 filters, and I think I bought the last box fan at any Target in the entire bay area.

My "creation": [https://i.imgur.com/jeJfqeW.jpg](https://i.imgur.com/jeJfqeW.jpg)

<comment> matt-attack Don't you want the filter on the incoming side? Air handling systems always put the filter on the inlet as far as I'm aware.

<comment><USER16> The main reason why furnaces and cars have it on the incoming side is because the dust and particulate can damage the engine/blower. So you want to filter it out before it reaches there. In a system like this, the box fan will not be damaged by the particulate so you can instead push the air through the filter instead of pull it.

</comment></comment></comment><comment><USER17> Can we talk about Molekule? Their team and some SF tech community folks have been plugging it all over Twitter during this tragic wildfire crisis. But it seems like snake oil to me. It's $800. Certainly for smoke particles it can't possibly offer any more protection than a standard HEPA filter. But even for its claimed ability to nuke VOCs, the claim seems ridiculous. While particles can deterioriate under prolonged exposure, the airflow must be too high and the exposure too short to make much of a difference.

What gets me is how these guys misuse "science marketing" to play on people's fears about germs. Add the shameless exploitation of a real tragedy here.

<comment><USER14> I had one. It has multiple issues:

1\. CADR is really low to the point where the unit is near useless due to #2

2\. In addition to a low CADR, it has the highest noise. It looks and sounds like a jet engine when you have this thing on high, which is needed due to the low CADR. This is the loudest air purifier that I've ever owned

3\. If you get a defective main filter, the unit will emit an unpleasant metallic smell. I haven't tested the particles yet but I doubt the air is clean.

4\. Unlike other smart air cleaners in the same price range, it's app and smart features don't work. You can't even create a schedule for it

It's a very flawed device

<comment><USER14> Forgot

5\. The unit works using some LED light. A. it is bright B. It is not replaceable. Meaning after 2-4 years of operation, the unit becomes a throwaway. This is not a good thing for a unit that costs over $700

</comment></comment></comment><comment><USER18> Note that restricting airflow on a radial fan can cause the motor to heat up. Make sure you get a 20-inch fan with a fuse. To reduce heat, increase air flow by making a box with three filters and by using 2 inch deep filters. Also, when I built my three filter "box" last fall, I was able to order a set of three MERV-13 20x20x2 filters directly from Nordic Pure for less than what they cost on Amazon. Finally, to make a cube, cut the remaining sides from the filter box. Then roughly tape it together with small pieces of duct tape. When the filters and panels are in the right spots, seal it completely with duct tape. Remember to put the box of filters on the "pull" side of the fan with right sides of the filters facing outwards.

<comment><USER19> I agree with placing the filters on the pull side, since that is what all hvac units do and what the filters are designed for. To be effective, you are also corrected that a deeper pleated filter with more surface area is the only way to go. But I am unconvinced the motor will heat up. Certainly there will be less air so if it is air cooled it will heat up from that, but at the same time, a fan in a partial vacuum uses less energy and should heat up less. Just slap a meter on it and you will see the draw can be significantly lower, since it is doing less work.

<comment><USER20> to perhaps reinforce your point: I put a filter on the front (as in this video) and the fan died a few weeks later.

</comment></comment></comment><comment><USER21> I spent the weekend researching, implementing, etc. air filtration as one of those affected by the CA fires. It was worth it!

The first step for me was getting a device to measure particles in the air. The air quality index (AQI) is an aggregate score that is made up of contributions from several harmful components. Of these, the quantity (weight/volume) of small particles (<2.5um) is often the large contributor. This is called the PM2.5.

Directly measuring PM2.5 is very hard, requiring a device that eliminates the larger particles from the air (typically a cyclonic separator it seems) combined with some way of capturing and weighing of the very small quantity of remaining particles (we're talking ug/m^3).

Many home air quality sensors instead measure the count/volume of particles _larger_ than 2.5 um and call that the "2.5um measurement". You can see the problem. I bought a laser particle counted called Dylos DC1100 Pro. The Dylos measures particles counts larger than 2.5um as is common, but also counts particles larger than 0.5um. Of these two numbers, the 2.5 count is only vaguely correlated with the actual PM2.5 measure, but the 0.5um count is highly correlated.

A bit of internet research (it seems many people have used the Dylos meter in various projects) and I was able to construct a scale to correlate 0.5um+ counts to PM2.5, and therefore AQI. (0.005*count~=ug/m^3)

OK, all that done, to the filtration. First, I installed 3M 1550 MPR furnace filters (~MERV11). The "1550" is a measure invented by 3M 'MicroParticleRating' (or something) and is supposed to speak to how well the filters remove small particles. However these furnace filters don't really knock down very small particle counts in once pass. Sure enough, putting the particle meter at an air duct, the large (2.5+) particle count was way down, but the small particle count was only down a little bit (15-25%?) from the ambient air. Net effect is that after running for several days my house numbers are about 1/3 of the outside air counts.

I also bought a BlueAir HEPA filter for my bedrooms. HEPA is supposed to be 99+% effective for particles 0.3um and up. This filter is in a whole different league. The particle counter placed on top of the filter returns near-zero small particle counts and does a much better job eliminating smells. The room they were in got down to 1/10 of outside levels.

Overall I'm glad I got both types of filters, we are sleeping better, and the meter was very helpful to understand what was going on.

<comment><USER22> Did you put the filter on the intake or outflow side of the fan?

I have built one of these (20x20 furnace filter on a box fan) and always put the filter on the intake side of the fan. However it seems like people are placing the filters on the outflow side of the fan instead, for reasons that are not clear.

Since it seems like you did some measurements, do you have any idea whether it's preferable to have the filter on the intake or outflow side of the fan? (I note that in furnaces and other air handling equipment, filters are almost universally on the intake, not the outflow, side, presumably because this keeps dust out of the blower/heating mechanicals.)

<comment><USER19> when you place it on the intake, it is sucked against whatever you are using to stop it pulling into the fan, if it is on the outtake, it can bubble out on the edges and the air can escape rather than pass through the filter. Intake is the only correct solution for these homemade devices without a metal diaphram.

</comment></comment></comment><comment><USER23> Nifty idea, but I'm not sure I agree with the technique used to prove effectiveness:

[https://www.youtube.com/watch?v=kH5APw_SLUU](https://www.youtube.com/watch?v=kH5APw_SLUU)

The narrator puts a particle counter in front of the fan and notes the 90% reduction. So far so good.

The problem is extrapolating this result to the entire room. Yes, maybe you'd get close to 90% if the device were allowed to run a few days.

On the other hand, it could leave the situation worse (by blowing existing particulates around) or unimproved (by failing to filter room air efficiently enough.

Either way, I'd like to see see a controlled study. Two identical rooms with identical usage. One gets a homemade filter. The other gets just a fan of the same make and model, maybe with a dummy filter to baffle airflow.

What's the average particle count in both rooms after, say one week?

<comment><USER24> If you check out Matthias wandel's YouTube channel, he does some experiments with hours-long recording of room particle counts. This is in a woodshop (sawdust) setting with a similar diy filter setup.

</comment></comment><comment><USER25> I do this and it works wonders if you have pets. Tips: \- run this homemade air purifier when you are vacuuming, as that tends to agitate particulates a lot \- get 2 filters, a cheap low grade and a premium, high-HEPA-rated filter. Stack them together and you can replace the cheap one frequently and the expensive one less frequently.

<comment><USER26> Does it go:

Fan --> Cheap Filter --> Expensive Filter

Fan --> Expensive Filter --> Cheap Filter

Cheap Filter --> Expensive Filter --> Fan

Expensive Filter --> Cheap Filter --> Fan

?

<comment><USER27> Cheap Filter --> Expensive Filter --> Fan

You put the filters on the intake, so that the airflow helps making a seal instead of creating leaks.

You put the cheap filter first everything that it catches will not clog the expansive one.

</comment></comment></comment><comment><USER28> I wonder if you'd put cotton wool, how effective it would be. Here is my set up:

\- I bought XIAOMI Mi Air Purifier 2 straight from China for $137.00 and spent 1 euro on a EU plug. It's so quiet that I can sleep next to it, looks nice and it's quite compact, so doesn't take up much space. It has a particle detector to adjust the fan speed. The app is useless, so a cheaper version without WiFi and bluetooth would be great.

\- Buy some HEPA filters to put into window ventilation. You may want to remove some plastic inside to increase the flow [http://img.archiexpo.com/images_ae/photo-g/69621-5895915.jpg](http://img.archiexpo.com/images_ae/photo-g/69621-5895915.jpg)

\- Buy roomba like vacuum cleaner [https://www.goodcheapandfast.com/articles/best-robot- vacuums](https://www.goodcheapandfast.com/articles/best-robot-vacuums)

It will cost you less than 500$ to buy these and about 55$/year for new filters. It is worth the money. The air quality is much better (I'm allergic and I haven't had any problem with my sinus since).

What is more, is it worth it. It will save you time cleaning your place (about 10h/year)

Anyone has tried robot vacuums with mop or automatic dirt disposal function?

<comment><USER29> > I wonder if you'd put cotton wool, how effective it would be.

Not very. Wet wool is better, but only as long as its wet and clean.

> XIAOMI Mi Air Purifier 2 straight from China

Interesting question. Does the removal of particulates offset the health impact of its cheap plastics?

<comment><USER30> Does anyone know what the actual smell of "chinesium" comes from? The smell of artificial rubber products from china, like remelt and cancer.

<comment><USER31> I bought a mechanical product like that one time and had to leave it outside for about a month before it off gassed completely

<comment><USER32> Happened to me, too. Once with a dog house, and again with a set of car floor mats. The floor mats are still out there.

</comment></comment></comment></comment></comment><comment><USER33> I made a custom wooden computer case with 8 120mm fans and a furnace filter over the intake. The computer side is positive pressure and is as clean as the day I built it 4 years ago.

I buy filters in bulk from McMaster Carr for $5 apiece.

<comment><USER34> Mcmaster carr[1] is a wonderful commerce website and I am so happy I found them. I buy all of my fittings and hoses and so on from them.

[1] [https://www.mcmaster.com/](https://www.mcmaster.com/)

</comment></comment><comment><USER35> Check out the blog

[http://particlecounting.tumblr.com/](http://particlecounting.tumblr.com/)

The writer has tested a lot of combinations of fans and filters (Simple, HEPA, Activated Charcoal). It's astonishingly easy to build a combination that costs _way_ less than a "professional" Air filter.

The writer has put his findings into a "social startup" that builts these simple, but very effective airfilters in some developing countries:

[https://smartairfilters.com/cn/en/product-category/diy- air-p...](https://smartairfilters.com/cn/en/product-category/diy-air- purifiers/)

<comment><USER36> I use the SmartAir filter setup in Shanghai. It works great and the founder's blog is very useful. I'm glad to support the project.

</comment></comment><comment><USER37> If anyone is looking for general air purifier recommendations. I'm a huge fan of Coway systems.

I have pretty bad allergies purchased a Coway Airmega 300 for my 850sq ft studio. I've had it for about 6 months and been incredibly happy with it. I wrote some initial thoughts about it here.

[https://productdork.com/t/coway- airmega-300-vs-400/56](https://productdork.com/t/coway-airmega-300-vs-400/56)

It has to be the best looking air filter on the market—I wanted something that would look good in my place when I have people over. Beyond that it is extremely well designed and the pre-filters are super easy to clean. I got mine on sale for about $400.

For smaller rooms the Coway mighty is a better and more affordable pick. It doesn't look as nice, but it is currently at the top of The Wirecutter's air purifier recommendations. You can find it on sale for around $180.

[https://thewirecutter.com/reviews/best-air- purifier/](https://thewirecutter.com/reviews/best-air-purifier/)

<comment><USER38> I have 2 of the $180 Coways and so far am pleased with them.

Once in a while, I will light a candle and when I blow it out, will hear the air purifier go on full-blast (Speed 3) to clear the air.

Interestingly, it sometimes turns to medium power (Speed 2) when I'm just shuffling around the room. I imagine its because I have a few rugs and its pushing up a lot of dust.

</comment></comment><comment><USER39> I wonder: if one is generally healthy and the air quality is unproblematic, should one get an air filter? Does air filtration potentially lower long term immunity and make us less tolerant to particulates?

I worry about the long term effects of being "too clean", that is, I think there's something to hygiene theory of disease. The body needs small stressors and perturbations in order to thrive.

<comment><USER40> I wouldn't worry about this if you live in a city. The amount of vehicle exhaust, brake dust, and just general stuff in the air will make up for and most likely counter the time you spend in a clean breathing environment.

</comment></comment><comment><USER41> I built a similar model over the weekend: [https://twitter.com/valarauca1/status/1061362369702445056](https://twitter.com/valarauca1/status/1061362369702445056)

Used an existing box fan. I had to buy duct tape ($3) and the filter I used one rated for 0.1micron pollen and viruses cost me $17 (rounding up after tax). I cut up a plastic safeway bag to make the seal around it. Seeing as most smoke particles is around 2.5-.5 micron I figured it'd be okay.

I threw this together at about 7am on Saturday after I woke up coughing my lungs out at 6am (I live in the bay area). Just a quick trip down the the Homeless Despot to get the parts and throw it together.

All things consider it works great. The air in my apartment is easy to breath, but if I leave without a respirator (even today) I cough uncontrollably.

\---

As of Tuesday evening it has been running for 4 days straight (no overheating). And has started to become noticeably brown. Needless to say I'm thankful for it.

</comment><comment><USER42> Where do you get these parts in the UK?

The MERV 13 20" filter is 140GBP on amazon.co.uk and 20" box fans are 40-50GBP.

</comment><comment><USER43> Is there an advantage to attaching the filter to the front of the fan so air is blown through it (as shown in the video) versus taping it to the back of the fan so air is sucked through it? Just curious if that would make any difference. It might be easier to get the filter to stay if it's getting sucked to the fan.

<comment><AUTHOR> I would guess that it works similar to a water pump- pushing is always more powerful than sucking - but check this out for some detailed analysis (and more data on DIY air filters) [https://smartairfilters.com/en/blog/where- should-an-air-filt...](https://smartairfilters.com/en/blog/where-should-an- air-filter-be-placed-relative-to-the-fan-for-best-efficiency/)

<comment><USER44> I never would've guessed turbulent air would be more difficult to push but it makes total sense! Great find.

</comment></comment></comment><comment><USER45> I used a very thick (4") filter rated for smoke particles when the wildfires this year blew their smoke down to Seattle. The filter went from white to a very interesting shade of grey in 3 days. Wife was able to sleep again though, so it does work very well in my experience. (20x20 fan, filter on intake side)

<comment><USER22> Out of curiosity, where were you able to find the big 4" thick filters in the 20x20 size? I wasn't able to find anything other than the usual 0.75 thick furnace dust filters in 20x20 for a box fan.

<comment><USER46> I just bought a 4 pack from Amazon Prime Now in SF, YMMV.

</comment></comment></comment><comment><USER47> I been pondering about this solution for months since my air purifier died back early summer. I also have an additional idea to make it more automatic by using a raspberry pi, hooking it up to a powerswitch tail (essentially cutting power to a fan) and have it automatically turn on and off depending on time of day, etc.

<comment><AUTHOR> I have mine on a homekit enabled outlet ($20) for scheduling and presence- based triggers. Unfortunately I haven't found a homekit enabled air quality sensor to pair with it.

<comment><USER48> Eve room? [https://www.evehome.com/en/eve- room](https://www.evehome.com/en/eve-room)

<comment><AUTHOR> Thanks! Last I checked they were no longer selling version 1 of this product and hadn't released version 2 yet. This might fit the bill.

</comment></comment></comment></comment><comment><USER49> Repurpose this device as a jerky dehydrator too: [https://altonbrown.com/beef- jerky-recipe/jerky-blowhard-3000...](https://altonbrown.com/beef-jerky- recipe/jerky-blowhard-3000/)

</comment><comment><USER50> They used to sell these--box fans with connections for furnace filters. I found it strange that they never caught on, and now you can't find them anywhere.

</comment><comment><USER51> I was looking up air quality monitors but can't seem to find any on amazon with a calibration certificate that will accurately measure 0.3 micro particles. Am I the only one who thinks this is a great opportunity for a smart product with an app that has the features of a professional air quality monitor and simple UI / UX? If such product exists, does anyone know where I can find it?

<comment><AUTHOR> With the recent California fires, I've been looking for a decent option. Unfortunately the Elgato Eve sensor is no longer sold, and the few other consumer products still hover in the $100+ range with poor reviews.

PurpleAir sells an indoor sensor, but it appears to be limited release and somewhat 3D printed. [https://www.purpleair.com/](https://www.purpleair.com/)

<comment><USER48> The new version of the Eve Room sensor seems to be out: [https://www.amazon.com/Elgato-10EAM9901-Generation- Technolog...](https://www.amazon.com/Elgato-10EAM9901-Generation-Technology- Temperature/dp/B07GKVBYKV)

<comment><USER52> How does Eve Room compare to the Netatmo Home Coach?

</comment></comment></comment></comment><comment><USER53> I've been running a 3M Filtrete MPR 2800 in my furnace filter. [https://www.purpleair.com/](https://www.purpleair.com/) confirms it works. There house averages maybe 60 PM 2.5 vs 200 outside. Don't know how good it is for furnace, but it hardly runs otherwise in Northern CA.

<comment><USER54> Do you have two air sensors, or do you just have one indoors and compare it with weather data?

<comment><USER53> I am relying on 2 purple air sensors 10 miles away in opposite directions for an outside estimate. They are usually within 10%, and we are in the same valley, so should be close. I also see when I stop the furnace fan, levels spike. Then drops when I turn on again...

</comment></comment></comment><comment><USER55> Edit: plants do nothing to particle matter in air they can soak up co2, benzene, formaldehyde etc but do ample resesrch before placing plants in your bedroom. Typically snake plants are fine in bedroom as they don't give out CO2 at night.

There is no need for an air purifier if you have ample light in your room. Just plant a few indoor plants

Peace lily

Rubber plant

Snake plant

Spider plant

Aloe vera

Money plant

Orchid

NASA has done a study in the 80s and these plants have purified a lot of harmful gases including Benzene, formaldehyde, CO etc

Please use more plants!! And on top of that few plants like Snake, Aloe give oxygen during day and night so they are refreshing (as in they don't just clean air they give oxygen as well) and plants are cheaper and require just water and fertilizer every once in a while.

I own 40+ plants in my balcony garden itself. I've experienced these effects first hand!

<comment><USER56> Apparently this NASA study needs a huge asterisk next to it.

[https://news.ycombinator.com/item?id=18193622](https://news.ycombinator.com/item?id=18193622)

<comment><USER55> What? I have read the report myself. They put in Benzene inside a sealed room and one of these plants. A few hours later the Benzene was gone! Absorbed by the plant.

They did the same with formaldehyde too and other harmful substances.

Isn't that the bar for purification? This is still better than mere air dolter that are costly and requore frequent maintenance

<comment><USER56> I think the key term here is _sealed room_.

And this does not invalidate the study, only helps evaluate the results in context of applying at home or office. I.e. it's still gonna help, but unless you restrict your airflow, not as much as you'd like.

Though the same caveat probably applies to all air purifiers too.

<comment><USER55> >Though the same caveat probably applies to all air purifiers too.

So whatever reservations you have against plants as air purifiers apply verbatim to commercial air purifiers. Then why the bias against plants?

Funny how you contradicted yourself, not to mention those downvoting me for speaking about plants and yet being enthusiastic about air filters!!

<comment><USER56> I didn't downvote you and I didn't contradict myself, I only posted a link that urges precise understanding of what the study does and does not show, and to what extent. I have no bias against plants or in favor of commercial air purifiers.

<comment><USER55> You did not downvote me. But you did contradict yourself.

On one hand you say the focus on NASA study is on the word "sealed". That would directly mean that you believe that plants as indoor purification would not be helpful if there was no sealed environment

And then you say that "the same thing would apply to air purifiers"

You clearly have a bias against plants, as do the few who downvoted me. I know you didn't downvote because HN doesn't allow you to do that!

The study which you have linked says that "more research needs to be done to check air purification" and guess what? They are going to do a study in a sealed environment because if a plant can remove Benzene, Formaldehyde and Toulene in a sealed environment then it can do the same when its not in a sealed environment. You cant5 shrug the results of NASA study saying "it was done in a n atypical environment", of course it was done in a sealed room.

The NASA study would have been refuted if no amount of Benzene was removed by plants. That'd mean that it is a waste of time and space for air purification, but they are not. Peace lily and Orchids removed Benzene. Period. Whether it was a sealed environment or not doesn't matter because results matter.

When a plant that costs less than 100$ has proven to remove harmful gases in a sealed room, I can't wrap my head around the logic of "debunking", the myth and going for a commercial air purifier that is costly af.

And why I say you contradicted yourself is that you criticized plants for being in a sealed room for being effective and then at the end you said "the same things apply to a regular sir purifer too"

This is exactly the fallacy Mr Trump had spoken to in a rally. He had said "I'll build a 100foot wall", the Mexicans will climb the wall, sure but they won't jump, unless of course they use ropes"

Yeah, they will use ropes and they will cross if they want to cross. That's not contradicting, it's a stupid logic.

Same issue with your case against house plants. "Keyword is sealed"

Which study has proven that air purifiers available in the market have done well in an aerated environment? The recommended way to use a commercial air purifier is to close doors and windows. __Same __issue as plants so if you recommend commercial purifiers over plants despite them both facing same shortcomings then you are biased against plants. End of story.

</comment></comment></comment></comment></comment></comment></comment><comment><USER57> So I did this with a cheap $15 box fan and a MERV 13 filter. It performs very poorly, the filter impedes the airflow too much and the fan actually will intake most of the airflow from the front corners of the output side because it's less resistance. Axial flow fans only operate efficiently at low static pressures. This is why your home forced air system uses a centrifugal blower, which is more efficient at high static pressures.

tl;dr I'd use a MERV 11 or less on a cheap box fan. You aren't going to make a Class 100 clean room out of your house with this kind of setup.

<comment><USER58> Your comment should be at the top of this thread. This guy never mentions fan performance after applying a strong filter like Merv 13. I did the same and the airflow is reduced significantly. Since other systems use a strong motor, this box fan contraption does not compare in the slightest. You'd have to have it run at high setting ALL the time. Imagine that...

</comment></comment><comment><USER59> Similar items are commercially available:

"The Fan Buddy is an electrostatic washable fan filter that attracts and captures airborne dust, pollen, dust-mite debris, lint, mold spores and pet dander. It will also help reduce smoke and smog. This Fan Buddy fits on most 20 in. box fans... "

[https://www.homedepot.com/p/Fan- Buddy-20-in-x-20-in-x-1-in-W...](https://www.homedepot.com/p/Fan- Buddy-20-in-x-20-in-x-1-in-Washable-Fan-Air-Filter-FB- BF-20/206210062#product_description)

</comment><comment><USER60> Might be a stupid question but does this work for external air pollution? I live at the 20th floor in a city with terrible air quality and we open the windows once or twice a day.

<comment><USER61> I imagine it would help with particulate matter (such as smoke, whether visible or not), but I do not think it would have any effect on gases such as ozone, sulfur dioxide or nitrous oxide.

<comment><USER28> That's correct. HEPA filters anything bigger than 2,5 μm e.g. [https://en.wikipedia.org/wiki/Benzopyrene](https://en.wikipedia.org/wiki/Benzopyrene) and NO2, SO2 etc. are 1000x smaller.

</comment></comment></comment><comment><USER62> I've been using a setup like this for the past year. I use a 4" think filter to reduce strain on the motor though (it's pleated, so a lot more surface area to pull air through than the thinner ones), the idea being reduced strain on the motor. I also stick a carbon pre-filter in front of it.

I get smoke wafting in from outside via window air conditioner - and I think my neighbor occasionally smokes in his room.

I'm planning to setup another to better cover my open floorplan.

</comment><comment><USER63> In case you're curious how this does with wildfire smoke -- Oakland 1 bedroom, put a 14"x20" MERV 13 (filtrete blue) filter on a box fan (covering the extra 6" with paper). Had a PMS5003 from adafruit monitoring before and after. In the span of 3 hours indoor PM2.5 dropped from 25 to 5 ug/m3 and has stayed low since.

[https://imgur.com/IxdxhV2](https://imgur.com/IxdxhV2)

</comment><comment><USER64> I have the ~$800 pro version early in the video. It's an IQAir. I bought it when I bought my house. We were refinishing the hardwood floors and have a small child. My goal was to knock down the VOCs to make the room safe for him prior to move in.

It runs 24/7 in my bedroom now. Huge improvement in sleep quality. I've only had to change one of the filters once for about $100 after 1.5 years of run time.

</comment><comment><USER65> I have been quite happy with the top pick from this review: [https://thewirecutter.com/reviews/best-air- purifier/](https://thewirecutter.com/reviews/best-air-purifier/)

Although the price of that purifier is now $40 more then when I bought it, so it may make more sense to look at their other picks.

<comment><USER66> I have the same one and think it's great. Bought it when the wildfires in British Columbia blew over and turned Calgary into an apocalyptic wasteland.

Air quality was bad and I'm still not sure what kind of filtering my condo building has.

</comment></comment><comment><USER67> Tried this exact same thing. Unless you are a "fan" of noise, and the inability to sleep next to it, go ahead. It's not worth it IMHO. I ended up just turning it on whenever I left the house, but even then my roommate started getting annoyed from the other side of the apartment.

</comment><comment><USER68> To what extent will a box fan like that successfully circulate most of the air in a room through the filter?

</comment><comment><USER69> Given how cheap the commercial ones are I'm not sure I see a point. Esp given the fact that the motors in box fans are unsuitable for the task.

I just ordered a wifi plug for mine though so that I can set it on a timer / hacked amazon dash button. It's not but the slight whoosh is annoying

</comment><comment><USER70> Over the past two years as BC and WA have had terrible forest fires, this exact solution has become quite popular for people who are willing to DIY. the air quality in mid summer 2018 in Vancouver was really quite bad, exceeding Delhi or Beijing pm2.5 figures for weeks.

<comment><USER71> Was Seattle as bad PM2.5 wise?

<comment><USER70> Yes...

[https://www.vox.com/energy-and- environment/2018/8/21/1776190...](https://www.vox.com/energy-and- environment/2018/8/21/17761908/seattle-air-quality-haze-smoke-wildfire-health)

</comment></comment></comment><comment><USER72> I have found this on amazon seems like someone is already build a complete prototype. [https://www.amazon.in/Smart-Air-DIY-Purifier- White/dp/B01CP5...](https://www.amazon.in/Smart-Air-DIY-Purifier- White/dp/B01CP55QXS/ref=pd_sbs_79_2?_encoding=UTF8&pd_rd_i=B01CP55QXS&pd_rd_r=979f7ddc-e969-11e8-8bb0-a509d9a0f381&pd_rd_w=fULSI&pd_rd_wg=QMAYi&pf_rd_i=desktop- dp- sims&pf_rd_m=A1VBAL9TL5WCBF&pf_rd_p=9fc668a0-2aac-4fb6-970f-606919bc0185&pf_rd_r=QA1DHXPWYMCWEE2HCYPG&pf_rd_s=desktop- dp-sims&pf_rd_t=40701&psc=1&refRID=QA1DHXPWYMCWEE2HCYPG)

</comment><comment><USER73> Do we have any other alternative to HEPA filtering, or something that last 5 years without me paying to replace it every 1 - 2 years? All the current Air Filtering system are like Printers, they earn more money with the yearly filter replacement.

I also wonder if it makes sense to have an Air Filter if I have my windows opened 80% of times? I like the better Air Circulation, but the Air Quality aren't exactly great either.

We now live in a world with pipes that have potential toxic materials and water contaminated so we need Water filtering system, and Air pollution that needs Air filtering system.

<comment><USER74> Particle filters such as HEPA are unfortunately by nature only effective for roughly 6 months, then they are clogged. You can vacuum them to get rid of the biggest particles and then use them for another 6 months (total 1 year), but then they are clogged at molecule level and are perhaps only 25% effective of its original efficiency and won't do you any good. The washable ones are not good and the ionization air purifiers without filtration are a scam. Particle filters are the best way to give you good air quality. And unfortunately you get what you pay for. When it comes to carbon filters they don't work for more than 6 months - no matter how good air quality you have. Carbon will absorb till it finds equilibrium then start to release smells and some gases. Shelf life of an opened package is about 6 months even if you don't push air through. Depending on the air quality in your local area (Bombay smog/wild fires/countryside clear skies), your filters will be clogged eventually and a rough estimation is 4-6 months in high polluted areas, and 1 year in less polluted areas). Turn the air purifier off when you have the windows open. It makes no sense to use it if you let pollutants in from outside, even if your indoor quality is bad.

</comment></comment><comment><USER75> Also works for dehydrating fruit:

[http://frugalvagabond.com/the-box-fan-dehydrator- experiment/](http://frugalvagabond.com/the-box-fan-dehydrator-experiment/)

</comment><comment><USER76> These work excellent. I put a finer filter on the output. Clear difference in the pollen seasons, but I just let it run all year and swap the (visually clogged) input filter every few months. The FPR10 output filter lasts longer, but you gotta take a look at the side facing the fan to inspect it.

Also, consider adding output filters on any AC units (ducting etc). Even a "new" AC system can quickly become a source of particulates, or (way) worse.

</comment><comment><USER77> Nice synchronicity that this was posted the same evening I got a ~160 USD Xiaomi Air Purifier 2 ([https://www.mi.com/global/air2/](https://www.mi.com/global/air2/)) delivered home. Might be a good alternative for those who want an off-the-shelf product, a pretty design and "smartness" like scheduling.

<comment><USER58> Scrolljacking on this site is unbelievable.

<comment><USER78> I didn't notice any? I just tried with my ad/tracking blocking disabled as well.

</comment></comment></comment><comment><USER79> I think this is a cool project idea, but I would not use this as a primary means to filter air unless you can't afford a proper hepa filter unit and you happen to have parts laying around to cobble this together. Smoke and mold are dangerous to breath and you only get one life. This is probably a good way to augment your existing filters, in my opinion.

</comment><comment><USER80> Wouldn't turning on the extractor in your kitchen have the same effect? If you've got the correct filter in there anyway.

<comment><USER81> If the filter type is right (as you mention) yeah that would make sense.

If it vents outside though, not necessarily. Running the extractor would drop air pressure and pull from elsewhere (particularly bad during times with low air quality).

</comment></comment><comment><USER82> Has anyone tried constructing a UV-C based filter before? You would need to be careful to make sure no light leaks out.

</comment><comment><USER83> When and for how long should I leave this turned on to be effective in removing dust particles in my small bedroom?

<comment><USER84> Are you ok with white noise while you're sleeping and air flowing in the room? If you're ok with those things, run it while you're at home and sleeping. If you go to work during the day turn it off then, and turn it back on when you get home. It should rapidly clean up the air in a small bedroom.

The only real issue is any continual air flow into the room. There will be a big impact from what kind of air system you have in the greater building. For example, central air without a good filter on that system will make your fan- filter's job a lot harder.

The filters are relatively cheap to replace and will last a long time filtering a small bedroom. I get a solid year out of the filter on my central air system and it's filtering an entire home (non-smoking, no pets). Outside of the small electrical cost or annoyance from having the fan running, there's no reason not to run it very frequently if you derive a benefit. If you don't desperately need purified air for eg allergy purposes and your small bedroom isn't receiving inbound air (eg from a central air system), run it for 20-30 minutes, a few times per day, and that should easily do the job. If that's a hassle, just let it run more often than not.

</comment></comment><comment><USER13> I worry about air pollution especially when I'm in Jakarta or Singapore so I bought the Dylos DC1700 air quality monitor. It is great to know exactly how bad the pollution is and how effective my air purifier is - I feel like I'm walking around with x-ray vision.

<comment><USER85> Know any merchant who sells Dylos DC1700? I'm in Jakarta too, kinda hard to find these kind of hardware

<comment><USER13> Sorry I don't know anyone who sells in Jakarta. I purchased it on Amazon.com and used the myus.com service to forward it to me. It's expensive but worth it for my health.

</comment></comment></comment><comment><USER86> That's a really good idea. I was planning to buy one for a few hundred dollars, but I should just do this instead. The burning season is really bad in Chiang Mai (lots of smoke in the air for about 2-3 months), so it's good to stay indoors and have an air filter.

<comment><USER87> Off topic, but hey so I just moved to Chiang Mai. Do you think it's worth even sticking around here during that time? I was thinking about just heading to Bali instead. Not sure how bad it really gets.

<comment><USER86> It's really awful, especially if you're sensitive. Some people aren't bothered by it too much, but it really affects me, so I try to get away. We have some pets, but it hasn't been too hard to find a house-sitter. (Although I always feel a bit guilty, and try to be honest about the smoke.)

These articles are concerning:

* [https://www.theguardian.com/environment/2018/aug/27/air-poll...](https://www.theguardian.com/environment/2018/aug/27/air-pollution-causes-huge-reduction-in-intelligence-study-reveals)

* [https://www.scientificamerican.com/article/air-pollution-a-l...](https://www.scientificamerican.com/article/air-pollution-a-leading-cause-of-ca/)

I think we'll move to a new city or country in the next 12 months. I don't think it's wise to go through burning seasons once a year for a few decades. (It's actually the only reason we want to move, otherwise Chiang Mai is an amazing place to live.)

Bali would be a good option, or even the south of Thailand if you have some more time on your visa. Koh Lanta is great.

<comment><USER87> Awesome thank you much for the links! It seems like a very awesome place so far. I'm loving it.

</comment></comment></comment></comment><comment><USER88> I've been luring the Dyson hot and cool air purifiers, it's pretty silent from what I've heard, it also serves as both an electrical heater during the winter and a cooler during the summer. The price tag is the reason I've never bought one...

<comment><USER89> > cooler during the summer

Where does the heat go?

<comment><USER90> It's just a fan + heater. It's not an air conditioner, nor is it marketed as such.

I have one. It works pretty well. The air filter isn't as good as the massive Austin Air I use for my living room, but it's okay for a smaller room... not to mention much quieter, smaller, and easier to integrate with home automation.

</comment></comment></comment><comment><USER91> How fast does this burn out the motor? Legitimate question. I _just_ built one of these.

</comment><comment><USER74> I've been reading and following these comments now and I'm both impressed and horrified at the same time. As a mechanical engineer, product developer and developing air purifiers specifically for 5,5 years in combination of filter expert till just 6 months ago. I now work in another industry. You can ask me anything and I'll do my best and be as unbiassed to brands as possible if you want me to.

There are a few things you need to know for your own safety if you do DIY and want to reduce costs: Fan and filter are the heart of the unit. This is where you put the money even if you want to do a temporary solution. The housing can be cheap, but please be smart and never leave a DIY unit alone since electricity is involved, they are not safe. Once you've bought all this equipment, you'll soon realize you have put out a cost of a reasonably good air purifier.

\- You need to have a good amount of space between the filter and the fan to cut pressure drop – otherwise you will overload the fan, you get a high electrical bill and it becomes a fire hazard or it will break down = your money is not well spent. This is why you see some units on the market looking hollow – the space is there for a reason. \- Fans. Look for a strong motor that can handle air resistance. Regular fans are not made for resistance and will break, stop (programmed) or even start a fire. Also look at the airflow rate and the safety regulations of it. The higher airflow rates the better. When it comes to fans, you get what you pay for. \- If you use a weak fan and a thick filter you will only clean the air closest to the fan, not the actual room air = money not well spent unless you use the purifier right in front of your mouth/nose. \- HEPA filters are actually not that great... There are newer filter types on the market that are less dense but still not as effective. HEPA can be too thick/dense for the fan to be able to pull air through, or the air doesn't have high flow enough to clean more than just the air next to the purifier. You need to have circulation. Especially fans that are made to only move air without resistance, the motors are not adapted for this. If you have a strong fan you can use HEPA (Merv) since it can power through. Also, if the filters are too thick, air leakage will occur, motor will sound horrible, and the air will pass on the side instead of through the filter = noises, whistle sounds and less clean air. Yes, duct tape is good here if you build it yourself. \- Put the filters in front of the fan (before fan) to spare the life of the fan – the dirt will not accumulate and destroy the fan over time. To get (collect) dirt in the filters is the goal. Some fans can handle dirt passing through and then you can have the filter after. However, if you just buy a regular air fan in a regular store, I don't suggest having the filter after the fan (air flow direction). \- If the filter gets super dirty quickly, you can vacuum or gently whip it outdoors to recover some lifetime. However, after some time (roughly 1 year in normal use) it will be clogged no matter what you do. There are no filters or technologies better than particle and carbon filters available today. The 6-months to a year lifespan is actually accurate in normal conditions. I've been doing these tests in China, India and Europe and US several times in different conditions (both lab standard and normal homes) and with different units/tech/brands etc and can confirm particle filters + ionization is the best tech available and the filters last 4 months-a year depending on local conditions. The filters are usually functional after a year as well, but with very low efficiency. \- Pre-filters are great since they take on large particles like pollen or ashes before it hits the main filter. Just make sure it's not too dense. \- Fully made air purifiers are tested by 3d party institutions unbiased to payments or commercial, certified and heavy controlled before released on the market. You can check consumer reports, AHAM and California Air resource board (ARB) or Chinese GB-standard websites for different type of tests and results if you want to know which ones are really, really good. Some complain that they are in "lab environments" but it's still really good products that does the job even in real life conditions. \- If the unit you want is not in their lists of tested products, it's a warning sign that the product is not good, or might not even qualify as an air purifier… It's a surprising large number of big brands that make terrible products but are good in marketing or simply rely on their names. \- Fully made air purifiers have fans developed specifically to match the filters resistance and won't break down after a few months or start a fire if put under heavy resistance (clogged filters). The filters last longer since its optimized for air treatment in home environments. Usually other technologies are a part as well such as ionization or UV or similar. That's why they are more expensive. They are super important in a development of air purifies. Some of them also have IP44 certified fans meaning they can work during humid conditions without breaking or causing short-circuit/burn outs or worse. \- These DIY things work, but are usually not cheaper in the long run and are not as effective as the real purifiers. If you suffer from fires, smog, allergies etc I highly suggest getting a real purifier incl filtration+ionization since those things are very harmful, especially for children. If you just like to temporary fix something these DIY will work if you do it right.

I hope I could answer some of your questions.

<comment><USER92> Thoughts on Photocatalytic Oxidation?

I have a Vornado's unit and the call it "Silverscreen."

</comment></comment><comment><USER93> I've been doing this for years. Cheaper drugstore fans can't handle the drag of the filter and will burn out. Kind of amazing that no one makes a box fan with slots for such a filter.

</comment><comment><USER94> Insanely simple idea when you think about it. Side perk: My furnace uses the same size filters, so it won't even be a hassle to stock ones that fit a box fan.

</comment><comment><USER95> Is there anywhere you can get a good blower fan for the purpose of filtering the air, instead of a box fan that has a lot of space around the blades?

<comment><USER96> Grainger [1] search for "industrial Blowers and Accessories" would probably be a good place to start looking. They tend to be expensive though. Take a look at McMaster-Carr [2] too.

[1]: [https://www.grainger.com](https://www.grainger.com)

[2]: [https://www.mcmaster.com/](https://www.mcmaster.com/)

</comment></comment><comment><USER97> Can those filter be washed? People living near car congested areas would benefit from them the most but should also swap them more often.

<comment><USER58> I don't think so. The filter he uses has to be replaced every 3 months and it costs ~$15 (that particular brand). So you are looking at $60/year in filter costs - all in all not bad! Also, you could stick a carbon pre-filter right in front of the fan (behind this filter) of it to filter out some of the odor- causing particles.

</comment></comment><comment><USER98> You've got to be kidding me. But yes, if you literally have a fan and a filter then why do you need to spend more money.

</comment><comment><USER99> Cool! You could use a smart plug and a fine dust (PM10 and PM2.5) sensor to start the fan only if the air is bad.

</comment><comment><USER100> That guy's wearing a doctor coat and has lots of books on the shelf so he is legit for sure. THUMBS UP.

</comment><comment><USER85> Is there a place where I can get information about the MERV rating of certain HEPA filter products?

<comment><USER101> MERV info: [http://www.mechreps.com/PDF/Merv_Rating_Chart.pdf](http://www.mechreps.com/PDF/Merv_Rating_Chart.pdf)

</comment></comment><comment><USER102> Does anyone know if this type of setup would be good for smokey air from California wildfires?

<comment><USER63> It works - we measured 25 down to 5 ug/m3 drop over 2 hours in an oakland townhouse. Measured with hobby grade (pms5003 from adafruit) hardware, so absolute numbers probably not that accurate, but the effect was clear.

</comment></comment><comment><USER103> I see some comments on fighting mold and smells, I have an experience devising my own protocol that was extremely successfull in my case.

Few years back I was desperate to find a large apartment in an area where they are just not available. I found one, extremely cheap, that the owner could not find anybody to rent to. The apartment was all but destroyed by previous occupants -- there was substantial mold in most rooms, heavy cigarette smell that was completely masked by even worse problem -- monkey pee and feces on every flat surface in the apartment.

Being geek I decided I will try what I can do and in the end I devised a protocol to treat the apartment. My girlfriend was very sceptical. A month later I brought her to apartment to the smell of fresh furniture and she was instantly converted. There was no fresh furniture, it was just the other smells were completely eradicated.

The only smell I could not get easily off and lingered for many months was banisters that were painted over with lacquer by the owner before I had the chance to treat them.

The treatment was:

1\. industrial ozone generator (200 USD) + 200W fan + air dehumidifier (ozone decays quickly in humid air) + programmable timer and remotely controlled (over Internet) AC socket to control fan and generator (this let me turn the fan for 20 minutes every hour and let me turn everything off 3 hours in advance so I can visit safely without being subjected to high levels of ozone). This setup was on for an entire month except for when I was visiting to do other stuff in the flat.

2\. 35% hydrogen peroxide mixed with baking soda. Ozone kills mold, binds and oxidises any smells except for urea crystals. To neutralize urea crystals you first have to dissolve them and treat while in dissolved state, before they crystalize again. I don't know what baking soda does, exactly (except for making cleanup tougher...) but I found dissolving some improves the treatment with hydrogen peroxide. I sprayed every surface (walls, floors, furniture, etc.) in the flat with this mixture enough to get it wet so that it dissolves and reacts with urea crystals.

Now, mandatory WARNING: both concentrated ozone and 35% hydrogen peroxide IS EXTREMELY DANGEROUS, you absolutely MUST spend time researching how to handle this stuff safely.

The hydrogen peroxide at that concentration INSTANTLY BURNS ANY ORGANIC MATTER IT IN CONTACT WITH. This includes your lungs and eyes if they come in contact with vapors or mist.

Concentrated ozone may also leave lasting effects on your eyes and lungs.

MAKE ABSOLUTELY SURE NOBODY ENTERS YOUR FLAT WHILE IT IS BEING TREATED, MAKE SURE OZONE IS NOT VENTING TO OTHER APARTMENTS, ETC.

One minuscule drop of 35% hydrogen peroxyde touched my finger and it felt as if I was shocked with electricity and the skin was instantly burned white. Don't even think about getting close to it without heavy nitrile gloves and face mask.

The fumes and mist will be extremely dangerous, I have used full face mask with external breathing aparatus to be on the safe side while I was spraying entire flat with it.

Test the effect on any surface before treatment and dilute with water until it becomes safe for that surface. I have destroyed some stuff at the kitchen where it reacted with plastic foil on otherwise metal oven exterior, etc. I ended up diluting it for everything except stained walls. For furniture I diluted it to around 5-6% hydrogen peroxide, for floor panels to around 9%.

ALSO, very important, 35% hydrogen peroxide naturally decomposes producing lots of hydrogen so if you store the containers for longer than few days you have to constantly monitor them and vent hydrogen before containers burst. Once you finish your treatment, get rid of it as quickly as possible -- it is a liability while you are storing it.

On the upside, and this was very important to me, this does not leave any lasting dangerous chemicals in your flat. Both the ozone and hydrogen peroxide decompose naturally into harmless products and baking soda is the only think you can really work to get rid of but only for cosmetic reasons -- so that your entire flat does not look as if it is covered in dust.

<comment><USER104> Hydrogen peroxide decomposes to water and oxygen, not hydrogen.

<comment><USER103> Ah, you are of course correct. Still, it will burst your bottle the same way hydrogen would.

</comment></comment></comment><comment><USER105> I use this same setup and it works great. Been doing it for years.

</comment><comment><USER106> I wonder if you can put a filter on both sides of the box fan.

<comment><USER107> There would be very very little gain from doing so, but you'd probably kill the motor.

HEPA filters are very very very good. Running through 2 of them isn't going to pull much more out because there just isn't much more.

Actually, you'd probably get less actual filtration due to the greatly reduced airflow.

<comment><USER106> Why would it kill the motor? Load is reduced when airflow is restricted.

If the first filter reduces 90% of pollutants, can we assume that the second filter reduces an additional 90%?

</comment></comment></comment><comment><USER108> Anyone knows how to DIY microfilters ? or even nanofilters ?

</comment><comment><USER109> At first glance this looks ridiculous until you realize it's a doctor from U of M's health center demonstrating its effectiveness

</comment><comment><USER110> mine brother too working in construction business and having same breathing problem.

</comment><comment><USER111> reddit.com/r/thereifixedit

</comment><comment><USER112> > "Videotaped"

haha. Seriously? It was on tape?!

</comment><comment><USER113> You could also buy a plant.

<comment><USER114> Plants don't remove particulate matter like an air purifier does

</comment></comment><comment><USER115> Hi

</comment><comment> black-tea Would this do anything to help with air pollution from a nearby road? I'm thinking particulates from diesel fumes.

</comment><comment><USER116> What kind of furnace needs this high level of air purity to operate? I would have thought a grating that prevents rats and squirrels from wandering in would suffice. I would assume small particulates would just burn with the rest of the fuel with no ill effects.

</comment><comment><USER117> literally HACKER news</comment>


Using Scala in Amazon Lambda for Processing Fastly Logs - <AUTHOR> https://tech.iheart.com/using-scala-in-amazon-lambda-15d30c562247#.fc5q2t42i <comment><USER2> "For java, there is absolutely some "jvm warmup" time that was noticed when there was low activity on the lambda function. To avoid this, we increased the frequency which Fastly was pushing S3 logs and we saw a 2x decrease in run time (from about 6 seconds to 3 seconds). "

Huh? Faster because AWS Lambda is now pre-warming JVMs, or just because it is keeping more of the said lambda function extracted from the zip file into the cache?

</comment><comment><USER3> > Firstly, only Java 8 is supported, so your build.sbt needs > to have some > configuration in it that enables 1.8 only > support

NONONONONONONONONO ! Who told you that? If you don't compile on Jdk 9 with target/source 9 it just doesn't matter which JVM version you use they should be Downwards Compatible, especially OpenJDK 8 which actually Lambda uses.</comment>


Ask HN: How much would you pay for an extremely scalable, resilient database? - <AUTHOR> Let's say that there was a database with a magic consensus protocol that allows it to easily scale from one to tens to hundreds to thousands to tens of thousands of nodes.
Tens of thousands of transactions may be performed per second, each taking about 1 to 4 seconds to be applied (sufficing for any use cases that are not necessarily near-real time).
The database supports procedural functions written in all kinds of hipster/systems-oriented programming languages, and may be bootstrapped to support all kinds of data structures and queries.
It was made to be developer-friendly as possible.
The database can run on minimal hardware, from as little as 512MB of RAM and 2vCPUs to more along the lines of 2GB RAM and 4vCPUs. The database may be hosted for a minimal cost.
The database is resilient in spite of all but one of your nodes crashing, allowing you to fulfill Tier 4 SLA agreements in terms of uptime without the need of a team of Site Reliability Engineers (SRE), or engineers with domain expertise in distributed systems.
My question to you in managerial or in development positions at small/large startups or enterprises in HN: how much would you pay for such a database?
How would the price differ if it was through a one-time/monthly licensing fee? What fee structure would you personally prefer?
If instead this database was bootstrapped around with a developer productivity framework like Meteor that would significantly speed up time-to-production, where you can build an entire platform - from backend to frontend - in a single codebase, would you pay more? <comment><USER2> I would prefer -

1). Either "open source code solution" \- allowing other members to fix, enhance, optimize the app.

2). OR, "one-time licensing fees with open source code allowing a change in code for own use case -AGPL"

3). "if monthly then - expecting constant updates and innovation on the product on a regular basis" to justify the subscription fees [still self- hosted and not on other parties cloud].

<comment><AUTHOR> Gotcha! Makes sense to me :). What price tag would you put on this software?

There's been a pretty interesting development from what I've seen on annual licensing fees for enterprise features, with the code open-sourced.

</comment></comment><comment><USER3> > The database is resilient in spite of all but one of your nodes crashing,

Well, once I hear that, I wouldn't be willing to pay anything. I admit, you did say magic consensus protocol. But by definition, this is impossible, unless you can reliably detect a node has gone down and isn't up and serving requests somehow. TBF that is to some extent possible. But a network partition will still take it down.

At a certain point, the biggest reliability factor is the complexity of the software, not the reliability of the hardware. You want the clustering logic as simple as possible. You need parts of query evaluation, hipster programming language evaluation, to be precisely deterministic.

<comment><AUTHOR> It would be possible if say for example, the database was fully replicated in a masterless fashion.

The tradeoff is slower writes (there are ways to make it so that the more nodes you replicate across, write latency won't be affected!).

Reads will scale linearly for the more nodes you replicate across.

So, the novelty in some sense is fast replication of data in a masterless fashion (without any leader such as, for example in Raft or Paxos).

If this protocol was surprisingly simple (which dumbs down the complexity of the software significantly), would you pay for this sort of database?

<comment><USER3> Yeah, no, the database being replicated "in a masterless fashion" doesn't help. The problem is that under some network partition conditions, you can't do some writes or any writes, unless you want to sacrifice resilience and/or consensus.

<comment><AUTHOR> Why wouldn't there be failures only under a complete network partition? So long as one node in one partition may communicate with another node in another partition, then writes may still be performed.

Availability would be what is sacrificed in the advent that a node is partitioned away from the main network.

<comment><USER3> Only when that's true of those two nodes and no other disjoint subset of nodes.

</comment></comment></comment></comment></comment><comment><USER4> I'm reading this post and really confused.if you have something, it might be easier to show it. It also seems like some of what you are selling is devoid of any understanding of the real world nuance and specificity that you encounter at scale.

Whatever you have built, clearly doesn't do all of these things today, if ever. What have you built or what are you building? How is it different, today, from whatever else is in the market.

I have a sushi restaurant. But, instead of us making sushi for you, we show you and your guests how to make it and by the end of the night, you're doing it like a pro and having a great experience, with wonderful food.

Then, we'll let you know if it's worth giving it a shot.

<comment><USER5> OP sounded very hypothetical to me - not asking as a startup idea...

<comment><AUTHOR> Yep! Just to clarify, this is entirely hypothetical! I want to know the value- add people would put on such a database if it were to exist.

There's little insight from what I've seen in the database market as to what people really want the most out of a database, or what makes a database "appealing" to people apart from its reputation from being time-tested.

</comment></comment></comment><comment><USER6> > Tens of thousands of transactions may be performed per second, each taking > about 1 to 4 seconds to be applied.

That is just too slow for anything that I would need. I'd be impressed with hundreds of thousands of transactions per second with double digit millisecond latencies.

</comment><comment><USER7> Difficult question.

But look at the closest competitors and see what they charge perhaps?

For example, take a look at Cockroach Labs, or MySQL InnoDB Cluster, or one of the many database as a service providers, or whatever you think is the closest competitor, and see what their licensing terms and pricing are...

</comment><comment><USER8> Look at the cost of existing databases that do this. Snowflake, Elasticsearch, etc. Their pricing models are public.

</comment><comment><USER9> One bajillion snake oil dollars.</comment>


MessagePack: the missing serializer - <AUTHOR> http://blog.treasure-data.com/post/12232702451/messagepack-the-missing-serializer

<comment><USER2> I've been very happy with MessagePack. It pretty much just does what I want it to: serialize and deserialize things in an efficient, streamable binary format. It can be used as a drop-in replacement for a lot of the things that I would otherwise do with JSON.

Also, the libraries are very good. It's not often you have similarly high- quality language bindings for Python, Java, and Haskell, among others, but that's the case here.</comment>