Cheap DIY Air filter

The guy who made this claims it is just as good as those over priced 11,000 RMB things but only costs about 166 RMB.

Might be worth a look for those so inclined.

http://particlecounting.tumblr.com/post/55483627230/how-to-make-a-diy-air-purifier

That just might work.

only thing is, with closed windows and plenty of plants, is it necessary in the home?
cant hurt to try it, stick filter on fan, theres no rocket science there!

i did consider putting filter over a window but where i am, its not that bad.

I wish I would have seen this before shelling out 400 bucks for one.

Alright, since no one else leaped out to say "I'll try one", I've decided to take the plunge and place and order.

I've also ordered a particle meter (cost a LOT more than the filter device ) so I can see how well it works.  Time to do some science.

I'm not sure how soon the filter device will arrive.  The meters were a little cheaper inside the US, so I'll be collecting that later this month.

I don't think it would work. Notice how, even with the fan still going, the numbers rose quickly just moving the reader about 20cm away from it? Useless.

we've actually brought those guys into the office (day time job) this past friday to run a few tests and build some of those babies to deploy on site.
The brought in the partible meter and all the other goodies, ran plenty of tests around the office and the verdict is that it works. You're not gonna get everything a 30K machine gets you but it' s pretty damn close.

I don't think it would work. Notice how, even with the fan still going, the numbers rose quickly just moving the reader about 20cm away from it? Useless.

If the fan can force air through a good hepa filter, I don't see how it couldn't have some sort of positive effect on air quality in a closed room.  In my mind, the question isn't "Will it make air cleaner" but "Does it clean enough air to significantly improve the air quality in a room?"

In theory, the air directly at the point of leaving the filter (in the one shown or in the finest and most expensive Blue Air unit) would be cleanest, but would mix with other air in the room as one moves farther away from the filter.  If the unit has just been recently turned on and the air speed through the filter isn't very high (not surprising for a hepa filter vs. a house fan), 20 cm would mean a lot of unfiltered air would be mixed with what's coming through the filter.  The video does state that the filter unit had just recently been turned on.

Once I have the filter device and the particle meter, I'll be testing both at point blank range and from across the room over a span of hours.  That should resolve any lingering questions about how effective it really is.

I'm told my filter unit will be shipped to beautiful Dongguan within a couple of days (I guess people in Beijing need these a lot worse than I do ).  I'll be bringing the same model of particle meter over from the US near the end of the month.


And, I see Noles jumped in before I got done writing.  I'm glad these seem to really work under Beijing conditions.  In comparison, DG air won't be much of a challenge.  I'll still be doing my own science experiment to see exactly how effective it is under my local conditions.

@ EL

That may not be of any value to you unless the wife moves somewhere else.  If she insists that all windows be open, you can not economically remove all the particulates in DG   

It arrived today. Getting me, the filter, and the meter all together will take a bit longer, but I'm ready to to a non-quantified test tonight, even if my lovely wife screams about there being no oxygen in the room.

My initial thoughts:

1.  A second strap would ensure a more secure seal between the front of the fan and the HEPA filter.

2.  More power Scotty!  The fan isn't supper powerful, plus a significant percentage of the air slips back around the outer edge of the blades.  Still, it should do some air cleaning.

I'll have plenty of time to test how exactly how well it cleans air in December.  I'm already thinking of some possible upgrades to the concept that should improve the overall efficiency.  Guess I should pick up a new roll of duct tape while I'm in the US.

I don't think it would work. Notice how, even with the fan still going, the numbers rose quickly just moving the reader about 20cm away from it? Useless.

They do 2 tests. The first, where he holds the counter in front of the filter to check that it's pushing air through, the second is where they leaving it running and then test the room at different intervals. Of course if he pulls it away the reading will change if it hasn't been turned on that long.

Search 'homemade air filter' if you want more proof, there are some scientists that suggested this first.

Sorry for the long delay.  Had a few difficulties with my Dylos particle meter.  First, I saved a little buying it in the USA - and found that the power block for it was NOT designed to handle 220V.   I didn't know anyone still made these things not designed to handle both 110 and 220 anymore.

Got another one with the correct voltage, etc from silicone heaven - but the point where the power plugs into a Dylos meter is very narrow so the rubber grip/insulator was too fat. 

Had my lovely wife go to the taobao shop that sells Dylos meters.  They didn't want to sell the power supply separately.   Told my wife to unleash her inner rottweiler.   They quickly relented and agreed to sell just the power supply.  Science was back in business.

Qualitatively, I could already tell it worked.  I sleep more soundly and wake up less congested.  Still, I wanted proof or I'd have to consider that I might be enjoying the placebo effect a little too much.

The meter backs up my personal view.  It shows a slow, steady reduction in particle counts.  Just to be sure, I tried closing the room without turning on the filter fan.  There was some reduction over time, but nothing like what the filter fan could do.

Now I've added to the available hardware.  There's a new model of air filter from these guys called "the Cannon".  I've never seen a fan quite like it.  It's powerful, yet fairly quiet on the low setting. Considering it's trying to ram air through a HEPA filter, higher settings don't really do much but add to the noise anyway. This version starts dropping the particles counts MUCH faster than the original model.  Costs about 500 RMB for this one.

There is one small issue in reporting this.  Particle counts here are wildly variable from day to day.  Rainfall almost always reduced them.  Other than that, it seems pretty random.  This means it is nearly impossible to run two tests from the same starting point.

I will say that both filter fans work, and particle count reductions range from a worst-case of about 80% to well over 90%.

Considering that I was about to drop 3000+ RMB on a nice model of air filter at a home appliance store, I'm very glad I saw this thread and took the plunge.  For much less money, I have a high quality particle meter plus 2 different filter fans.


My ideas for designing a super-version of this have slowly evolved.  The limiting factor is how much air you can get to go through the hepa filter.  Both versions of the DIY type employ a round fan and a square filter, thus losing a lot of the available filter surface.  What I have in mind should resolve both of these issues.  The target is to at least triple the air flow rate while adding a few other features.  The tradeoff is losing easy portability and having to shell out some cash at the local metal shop for a bit of custom work.