Experiments on a $50 DIY air purifier that takes 30s to assemble • Hacker News Board

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#91

Post by post_break » Thu, Dec 17, 2020, 4:56 PM UTC

rootusrootus wrote: post #89

westurner wrote: post #54

From "Better Box Fan Air Purifier" https://tombuildsstuff.blogspot.com/2013/06/better-box-fan-a... : > Air purifiers can be expensive and you've probably seen articles recommending to just put a 20" x 20" x 1" furnace filter on a cheap 20" box fan and POOF! instant cleaner air for not a lot of money. It really does clean the air pretty cheap. > There's a problem with this though. These fans weren't designed to be run…

> we'll use two 20x25x1 filters which increases the filter surface area over 250%. That seems like an overly complicated first attempt, why not just switch to a 20x20x4?

Those can be harder to source I've found. Cheaper to use two filters than one as well since you can replaced the prefilter more often.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#92

Post by dbsmith83 » Thu, Dec 17, 2020, 5:00 PM UTC

Love the data on this experiment. I made one of these during the wildfires, and it was apparent that it was working after just a few days. The once colorless filter had become noticeably grey/yellowed.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#93

Post by azmodeus » Thu, Dec 17, 2020, 5:00 PM UTC

cinntaile wrote: post #27

azmodeus wrote: post #23

Earlier quoted context omitted.

It would be nice if preassembled kits could be purchased from you. I would be happy to pay USD 40 for a good preassembled kit.

The BOM already costs more than USD 40 so USD 80 is probably a more realistic number for a preassembled kit.

Would be happy to pay USD 80 for it as well

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#94

Post by turtlebits » Thu, Dec 17, 2020, 5:03 PM UTC

ocdtrekkie wrote: post #85

I used a 20x20x1 taped to a box fan for over a year as an air purifier because I had ferrets, and ferrets leave a particular odor floating about most of the time. I didn't want to use an odor-removing filter with charcoal on my furnace because they're super thick and put strain on the motor, and I don't care about the box fan. It worked really well, probably the biggest challenge was securing the filter to the fan: I…

They sell silicon bands designed to keep the filter attached to 20" box fans. They're <$10 and work well.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#95

Post by rootusrootus » Thu, Dec 17, 2020, 5:10 PM UTC

Traubenfuchs wrote: post #41

chopin wrote: post #19

What I am wondering about: I worked with and designed clean room equipment in the nineties. I remember that HEPA requires a considerable pressure difference which cannot be delivered by an axial fan. You'd need a radial one which can deliver a considerable differential pressure, at cost of throughput (where the axial fan shine). If you strap a HEPA to an axial fan and seal it, the fan runs effectively "empty", i.e. i…

> In a normal room you can see the laser beam in dark. Dear god, do you live next to a coal plant? I would argue that in a normal room one should NOT be able to see the laser beam!

Red laser, sure, but in my experience green lasers are significantly brighter and it's much easier to see the beam in clear air (though if you're human you probably need to look down the beam to spot it, my cats can see the beam horizontally and they swat at it).

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#96

Post by esaym » Thu, Dec 17, 2020, 5:11 PM UTC

Scene_Cast2 wrote: post #84

I did a bit of experimentation with different filters for a DIY build like that. Setup: I tried out a bunch of different air filters in a medium-sized apartment. Two objectives: how fast PM2.5 is removed, and down to what level can it bring down PM2.5. From worst to best: * Nordic Pure 20x20x4M15+C MERV 15 - the carbon layer absolutely kills airflow, doesn't work * Filtrete 20x20x1, AC Furnace Air Filter, MPR 2800 /…

I've been using the Nordic Pure filters for many years now. Way better (and cheaper) than the stuff you get at home depot, etc.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#97

Post by nitrogen » Thu, Dec 17, 2020, 5:21 PM UTC

input_sh wrote: post #80

platz wrote: post #65

Earlier quoted context omitted.

Usually this means the company does not sell to consumers and is b2b only, similar to how you just can't buy something anonymously online from a wholesale distributor.

Usually, but you have three buttons on the first screen of their homepage: for schools, for offices, for homes . I don't think they're only b2b.

That could still be targeting manufacturers of products for those three categories.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#98

Post by acvny » Thu, Dec 17, 2020, 5:23 PM UTC

Wait. I did the same thing and after running the filter for several months, when I disassembled it, the filter was clean as new, but the bulk of the dust was laying somewhere between the blades and the motor and on the edges of the fan. It is very hard to actually get the right type of fan and assemble it correctly because simple fan will not work (the air will flow over the blades, thus not providing the required suction so that the air passes through the filters). The filters have pretty high resistance so you need a very efficient sucking / blowing fan to make the air pass through.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#99

Post by rootusrootus » Thu, Dec 17, 2020, 5:23 PM UTC

nether wrote: post #66

The downside is that these filters sell out in places where there are fires. So the time to buy them is now.

I agree. When we had wildfire smoke descend on our area, the stores sold out within hours. If you live in an area which routinely experiences wildfire smoke, it's worth stocking a few filters, both 20x20x4 for box fans and whatever size your furnace uses. It made a huge difference to have fresh filters to swap out every few days.

Re: Experiments on a $50 DIY air purifier that takes 30s to assemble

#100

Post by nkurz » Thu, Dec 17, 2020, 5:23 PM UTC

causality0 wrote: post #78

Reading the graph, it looks like it took both purifiers a full twenty minutes to make the air as clean as it was before the fans kicked all the particles off surfaces and into the air.

Are you making a joke, or did you perhaps miss the description of the expiriment that involves burning a piece of incense when he starts the test? I agree though that in a more formal test, a "null" version without the incense would be a good comparison.