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Build a do-it-yourself home air purifier for about $25

uofmhealth.org

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Re: Build a do-it-yourself home air purifier for about $25

#61

Post by ex_amazon_sde »

io_io wrote: post #6
smmnyc wrote: post #2

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.

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...

Excellent page.

Re: Build a do-it-yourself home air purifier for about $25

#62

Post by clairity »

leon_sbt wrote: post #47

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 cloggin…

> “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), 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.

Re: Build a do-it-yourself home air purifier for about $25

#63

Post by valarauca1 »

I built a similar model over the weekend: 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.

Re: Build a do-it-yourself home air purifier for about $25

#65

Post by TylerE »

tra3 wrote: post #64

I wonder if you can put a filter on both sides of the box fan.

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.

Re: Build a do-it-yourself home air purifier for about $25

#66

Post by adventured »

joezydeco wrote: post #18
adventured wrote: post #10

Earlier quoted context omitted.

Perhaps strain on the cheap box fan motor as it tries to pull its air through the filter. I've gone through a number of those style of cheap box fans over the years, any kind of long-term resistance very near the intake seems to cause the equally cheap motors harm and shorten their functioning life considerably. I haven't seen the same motor damage problem with resistance added to the exhaust side. In absence of that…

I'd agree with this. I used to put the high-efficiency filters on my furnace, my HVAC guy said these filters are so heavy that they put a strain on the blower motor. It's better for the motor to use a plain blue fiberglass filter (MSRP $1). You're not really filtering that much out of a closed house, unless you run your forced-air A/C or Heat with the windows open.

I did the same thing with my furnace. Just to try it I switched to a high merv filter rating and could immediately notice the considerable reduction in air flow that it was causing (and presumably increased strain on the furnace). Seeing as it was a bit more restrictive than I expected, I ended up ditching that and going back to a weaker merv rating filter (haven't gone back to the blue fiberglass style filters, just going with a weaker merv seems to do the trick, haven't had any problems with increased wear on the furnace in the last ~8 years).

Re: Build a do-it-yourself home air purifier for about $25

#67

Post by dwd »

leon_sbt wrote: post #47

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 cloggin…

The purifiers I use have the activated charcoal before the HEPA. Probably doesn't matter that much though I sometimes findd a small amount of dust leakage from the pre-filter screen on the carbon filter which would just clog the HEPA.

Re: Build a do-it-yourself home air purifier for about $25

#68

Post by jryan49 »

peepopeep wrote: post #39
pwarner wrote: post #31

Earlier quoted context omitted.

https://www.purpleair.com/ seems to work great for me!

Can the sensor be used indoors or does it have to be their "indoor sensor"? The products look interesting but the site does not inspire confidence.

I'm using their indoor sensor, works well

Re: Build a do-it-yourself home air purifier for about $25

#70

Post by blattimwind »

ed_balls wrote: post #52

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 gr…

> 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?

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