
A small DIY air purifier - Rondom
https://github.com/Kels316/DIY-Air-Purifier
======
lmilcin
Air quality test before and after or it doesn't work.

I am very suspicious with regards to air purifiers. Have you ever seen real
HEPA filter? It is thick and it is quite difficult to push air through it. I
can't imagine small PC fan that is designed to push air through UNOBSTRUCTED
space will make any significant flow of air. I have spent some time with the
guys who build PCs and who know great deal about fans and one thing I learned
even an object that the air has to pass around or any kink in the path of air
can severly impact performance of PC fan. Because they are designed to be
quiet and still provide good flow of air they produce almost no pressure
differential to speak of and the flow can be halved by a wire mesh that is a
bit too dense.

You need to cycle the air in your room through the filter couple of times to
clean it, assuming your filter is any good.

The cheap fan in the picture would barely be able to cycle the air in a small
room maybe once an hour, if it was completely unobstructed. It is very likely
that with any kind of HEPA filter the flow will drop by an order of magnitude.

Go with suggestion of other readers. If you want good, cheap filter, use a box
fan and especially one that was designed to give good pressure difference.
Take large cardboard or plastic box and mount large HEPA filter in it so that
the air has to pass through. The larger the surface of the filter the easier
time the fan will have to push the air through it and more efficient it will
be.

~~~
0-_-0
> Because they are designed to be quiet and still provide good flow of air
> they produce almost no pressure differential to speak of and the flow can be
> halved by a wire mesh that is a bit too dense

There are high static pressure fans which address this problem, specifically
designed to work with pressure differential, usually used to blow air through
radiators for water cooling. The fan linked in the github page (Noctua NF-F12,
the "cheap fan" in the picture) is such a fan, it provides a static pressure
of 7.63 mmH2O, which is very high.

Edit: you can get regular-sized 12cm pc fans that need 48 watts and rotate at
7160rpm, move 7.160 m^3/min air at 35.877 mmH2O static pressure:

[https://www.frozencpu.com/products/8147/fan-500/Delta_Mega_F...](https://www.frozencpu.com/products/8147/fan-500/Delta_Mega_Fast_120mm_x_38mm_Fan_-_252_CFM_-
_Bare_Lead_PFB1212UHE-F00_No_RPM.html?tl=g36c435s1109)

~~~
avian
> it provides a static pressure of 7.63 mmH2O

If anyone else is wondering, that's about 0.8 mbar (roughly 8 ten-thousands of
an atmosphere), or 80 Pa of over-pressure.

To put this into perspective, my local atmospheric pressure varied about 2000
Pa in the last 48h due to weather changes.

~~~
wlesieutre
Lemme go send my air intake through a time machine and as long as the weather
keeps changing we can use that to drive air through a filter!

~~~
avian
No need for a time machine (or being snarky - I did say it's just for
comparison, didn't I? I think it does put the "very high pressure" into
perspective)

That said, your time machine idea could be simply implemented with a large,
airtight box. Simply put the filter over it and weather changes will push and
pull air through the filter with two orders of magnitude more pressure than
this little fan. Volume of filtered air will depend on the volume of the box
though, so better get a large one.

------
kn100
This is a really cool project but frankly you can do it a lot cheaper. Find
the cheapest box fan you can find, and find the cheapest HEPA filter you can,
and strap the HEPA filter to the front. To improve air purification even
futher, slap an activated carbon filter on the front too, and your air
purifier now filters VoCs! For cheap Activated Carbon Filters, look into the
kind used for Aquarium filters. They'll work just as well for air as far as I
know.

In China there is a whole company founded on doing just this, although they've
since pivoted into selling specific air purification hardware at a significant
discount. See: [https://smartairfilters.com/cn/en/product/diy-1-1-air-
purifi...](https://smartairfilters.com/cn/en/product/diy-1-1-air-purifier/)

~~~
post_break
If you want this to actually work, you take a box fan, and 2 filters. You make
a triangle and then some cardboard on the top and bottom to fill the gap. This
increases surface area and reduces the stress on the fan due to pressure drop.
Slapping a filter directly on to the box fan is going to kill the fan very
quickly. [https://i.imgur.com/SX1RloH.jpg](https://i.imgur.com/SX1RloH.jpg)

~~~
opencl
I ran a few cheap box fans with filters directly over them for several years
and none of them failed, I have heard this claim a lot but it seems
overstated. The triangle setup _will_ significantly increase the airflow and
thus the effectiveness of filtration though.

~~~
post_break
I guess it depends on the quality of filter. If you're rocking a high merv
filter for smoke the pressure drop can be significant.

------
majos
May as well ask here: do air purifiers have meaningful health benefits for
generally healthy people? I get that you change the filter and it's filled
with grey muck and that's gross, and that the filters change particulate
content in air, but is there good evidence that doing those things improves
health if you don't already have some sensitivity to air pollution or live in
a highly polluted area?

I don't know if "Lung India" is a great journal, but the "Efficacy of indoor
air filters" section of this paper [1] doesn't offer much support. All studies
are pretty small and focused on people with asthma or pet allergies. The few
studies of populations without such conditions show what look to me like minor
improvements, e.g. a ~5 mmHg drop in blood pressure. These aren't super strong
studies though.

The argument that pops up in pro-air-filter pieces draws a line through "air
pollution can be a big health hazard" (true), "air filters reduce some
particulate content in the air" (true), and "air filters improve health"
(unclear). But the "big health hazard" conclusion seems to come from intensely
polluted environments, like poorly-ventilated homes that use kerosene, or
areas with lots of smoke. For a generic first-world home I can't find much
evidence.

[1]
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4587002/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4587002/)

~~~
sl1ck731
I would assume the majority of people (in the US, anyway) are already
filtering their air enough through their central air to make any additional
"room-sized" filtering negligible.

Similarly they make some very dense HVAC filters if standard ones aren't
catching the level of particles you need, so I'm not sure what the purpose of
these filter-fan things are for _most_ people.

~~~
lotsofpulp
>Similarly they make some very dense HVAC filters if standard ones aren't
catching the level of particles you need, so I'm not sure what the purpose of
these filter-fan things are for most people.

These are a scam, especially all those 3M filtrete ones. Air handlers in homes
and most other HVAC applications are not made to also serve as tiny
particulate filters, so it will make the whole HVAC system slow or even stop
since it won't be able to get the air flow it needs to function.

~~~
djannzjkzxn
I believe you that the HVAC isn’t designed for such a filter. But a few months
back my home was in the path of smoke from some wildfires. The AQI went from
200 to 0 after I installed a filter and ran the house fan for an hour. Also,
the furnace doesn’t have to work very hard here because of the mild climate,
so I never have much of a heat bill anyway. It would be a bummer if the
furnace died because of it running out of spec, but I’m skeptical that the
risk-adjusted cost of that is higher than the cost of standalone filtration
units.

~~~
lotsofpulp
This page has a decent explanation of the problem:

[https://www.pvhvac.com/blog/whats-the-best-air-filter-for-
yo...](https://www.pvhvac.com/blog/whats-the-best-air-filter-for-your-home)

All the commercial HVAC technicians I speak to say to use the cheapest non
fancy filters if your goal is to maximize life of the HVAC system, but I'm
sure it all depends on everyone's specific system and how the return is and
whatnot.

------
chewz
This seems like useless toy.

You should be aiming for something larger that would work for an apartment.

[1] [https://youtu.be/kH5APw_SLUU](https://youtu.be/kH5APw_SLUU)

[2] [https://youtu.be/8Hkdpx-59kk](https://youtu.be/8Hkdpx-59kk)

There is thousand vidoes on Youtube on how to DYI one.

~~~
dredmorbius
The problem for areas presently affected by high PM2.5 concentrations, most
notably Australia, is that materials which are commonplace in the US, box
fans, but especially box-fan-sized square HEPA furnace filters, are rare as
hen's teeth.

So alternate designs using available materials are required.

(Or someone might drop ship a few containers worth of box fans and HEPA
furnace filters down under.)

~~~
brnt
Same problem here. I've just spent close to an hour trying to locate a box fan
for sale in Europe, couldn't find any resembling those I can easily find on
amazon.com!

------
loldot_
I don't know how effective they are compared to these devices, but I much
prefer to keep plants with air purifying qualities. NASA did a study on a
variety of air purifying plants in 1989:
[https://ntrs.nasa.gov/search.jsp?R=19930073077](https://ntrs.nasa.gov/search.jsp?R=19930073077)

~~~
minikites
You would need to live in an indoor rainforest (approximately 680 plants for a
typical house) to see an effect on air quality, a spider plant in the corner
isn't doing anything:
[https://www.youtube.com/watch?v=AmeiXikh0v8](https://www.youtube.com/watch?v=AmeiXikh0v8)

~~~
csytan
*to see a similar effect on air quality as mentioned in the study

------
storyinmemo
This project would take 2-3 days to filter the volume of air in a 1,000 sq
foot apartment... which is to say it would do nothing of significance. To be
effective, you want to change the air something closer to once every 30
minutes.

~~~
crispyambulance
I agree that it would be silly to expect this thing to purify air for an
entire living space.

With a few adaptations, however, it might be good as a soldering station fume
extractor. These already exist and are little more than a tube, a fan, and a
filter (usually with activated charcoal).

The nice thing about this one is that it's circular and could easily adapt to
a flexible tube and you could perhaps stack fans for greater sucking power.

------
adrianN
You could probably buy a box fan and tape a HEPA filter in front.

~~~
packetslave
This works shockingly well. They were quite popular during last year's
California fires when "real" air purifiers were sold out everywhere.

~~~
starpilot
Also worked well in Seattle last summer.

------
JonathanFly
Is that little fan really effective? I just duck taped a furnace filter to a
20 dollar box fan. No 3d printer needed.

Just did this recently actually here's a pic
[https://mobile.twitter.com/jonathanfly/status/12155378275654...](https://mobile.twitter.com/jonathanfly/status/1215537827565490176)

------
qpiox
Pollution sensors for indoor use that can be plug via USB to the mobile phone
are really cheap, you can find laser ones like Nova SDS for $17 and some that
are not so precise come even cheaper than that.

So unless the author buys a real PM2.5 sensor and does a test in a true room
and not a box of the size of a Desktop PC, with the sensor on the opposite
side of the room, and proves that the pollution drops to below 8micrograms/m3,
in a reasonable time frame, than we can say that it is working.

Until than we can only say that the purifier is only able to purify a desktop
PC.

------
bureaucrat
Not enough airflow to filter air. Really, it's just an expensive way to waste
money.

Seriously? 600mA? Air purifiers are rated like 30W for a reason.

------
toastal
I'm in Bangkok right now which is having a smog issue right now due to
pollution and burning in the rice fields across the country. It's a shame that
we're buying/making air filters instead of working on policy and cleaner
methods of doing work--so now the poor and the wildlife can't afford to have
clean air.

~~~
overcast
There are cleaner methods, stop taking the easy route and burning everything
down.

------
spookthesunset
In addition to the old "strap an HVAC sized air filter on the front of a box
fan" tip, I'd add that it is important to maintain a positive air pressure in
your living space. The only path air should enter your dwelling from the
outside is via your air filter.

You can do this by putting the box fan in a window and sealing up any gaps
with something like cardboard or thick plastic sheeting. On the outdoor end of
the fan, put your filter. Close all other windows & doors in the house.

Keeping a positive indoor air pressure this way makes sure all the air in your
house is filtered. Obviously you'll want to make sure your box fan's filter is
rated for smoke / particulate matter.

~~~
dredmorbius
Bad advice.

A decent filter's throughput is going to be multiples of your structure's air-
exchange rate.

What you want to do is to _filter the interior air_ , by passing it, multiple
times, through the filter. If you put the fan and filter in a window, you're
hugely multiplying the air-exchange rate (to no net benefit), but are
_filtering_ that air only once.

The net result is a much _higher_ indoor particulates level.

So no, don't do this.

~~~
spookthesunset
Interesting perspective. Wouldn’t it be best to do some combo of both? A low
volume fan/filter that maintains positive pressure and an internal filter/fan
combo?

I mean in labs and manufacturing facilities that need ultra pure air, I’m
pretty sure they maintain a positive pressure inside the sensitive areas.
Otherwise you’ll be sucking in bad crap from every nook and cranny...

~~~
dredmorbius
Various lab setups have different requirements.

For biocontainment you generally want _negative_ pressure, such that all
_exhaust_ is filtered.

For clean rooms, positive pressure, to ensure filtration and minimum particle
reduction levels within the conditioned space. These also have staged zones,
much like a cascade refrigerator, with finer levels of purity as you approach
the core. Humans themselves are excluded from the higher-purity zones (we're
leaky bags of flakey skin, hair, dander, sweat, and mucus). Most especially in
chip-fab, but also I suspect various nanofab facilities.

All of which is pretty much entirely outside my paygrade, so I can't really
comment intelligently.

------
jwr
I would suggest worrying much more about PM2.5 and getting a filter that does
trap those particles. Many health problems are caused specifically by small
particulate matter.

~~~
mrspuratic
His statement "I'm not concerned with the ability of the device to remove
PM2.5" comes across as dismissive - he's not concerned because he's using a
HEPA filter health officials are recommending and therefore he trusts it. HEPA
starts at 0.3μm ("PM0.3") particle size, which doesn't cover finer forms of
elemental carbon (soot). "H13" is a minimum retention efficiency though, not a
specific particle size or application.

------
vladocar
Here is similar idea:
[https://www.aliexpress.com/item/32989809211.html?spm=a2g0o.p...](https://www.aliexpress.com/item/32989809211.html?spm=a2g0o.productlist.0.0.43497b069dZbSy&algo_pvid=2afaf365-792a-4bb2-9d1b-dcc2a10a062f&algo_expid=2afaf365-792a-4bb2-9d1b-dcc2a10a062f-0&btsid=7dc87566-75e8-4331-b4c7-07d5b6c2018c&ws_ab_test=searchweb0_0,searchweb201602_6,searchweb201603_53)

------
littlejohnny
How about a 'filter' that can 'wash' the air with clean water. To me it
appears to me the best possible solution to clean air in a confined space. To
put it simply, air can be bubbled through the clean water, to scrub it of both
particulate and chemical contaminants. No doubt the apparatus will lend itself
to several technical challenges like noise and the need for periodic changes
of the water.

I believe such air purifiers already exist.

~~~
dredmorbius
See: [https://venta-usa.com/product-category/airwashers/](https://venta-
usa.com/product-category/airwashers/)

They do an excellent job of humidifying the treated space, which may or may
not be ideal.

~~~
littlejohnny
dredmorbius, do you own one? At what frequency do you normally change the
water?

~~~
dredmorbius
No, I don't. Ran across them discussing filtering options recently.

------
dredmorbius
A group has come up with an alternative design, with a far higher flow rate,
and similar in concept to US-based box-fan + furnace-filter designs (materials
for which are _not_ readily available in Australia), with workshops in
Canberra, described here:

[https://www.eventbrite.com.au/e/making-your-home-smoke-
proof...](https://www.eventbrite.com.au/e/making-your-home-smoke-proof-diy-
air-purifier-workshop-tickets-88598234705#)

Materials for DIY Air Purifiers are:

\- Floor Fan of any variety (BYO or we will be providing options for large and
small fans)

\- PM2.5-suitable Air filter (we will be bulk ordering the best type of Ryco
MicroShield Cabin Filters for this purpose)

\- Carboard & tape (we will provide these materials)

Efficiency of the US-based version seems to be quite good:

[https://invidio.us/watch?v=kH5APw_SLUU](https://invidio.us/watch?v=kH5APw_SLUU)

------
sampo
What do you think about air washers? In addition to air filters, they blow air
over wet surfaces to both clean and humidify the air.

Here is one from Phillips:
[https://www.youtube.com/watch?v=n3xC3qxVphw](https://www.youtube.com/watch?v=n3xC3qxVphw)

~~~
bipson
I have one of those.

It does not "wash" the air. It has a HEPA-filter on the intake side before the
humidifying cycle. So it is basically the same thing as all other examples on
this comment page.

You can actually run it without water (which we do), then it does only
filtration.

Don't buy this particular product. It is overprized and has dramatic
production quality issues (we sent two back, amazon reviews indicate larger
issues).

------
clarry
Speaking of air purifiers, does anyone have recommendations for one that is
quiet and still effective?

I have a pair of Electrolux EAP300s, in small rooms.

Unfortunately on the lowest manual setting ("Quiet") they hardly do anything
for air quality. And they're still louder than I like. I think they really
optimized for cost; these devices feel very light and plasticy, the fan sounds
cheap and has an uneven tone to it, and its speed keeps oscillating back and
forth. The purifier itself is also not stable and it can make an annoying
noise if placed on a surface that ends up vibrating along.

I also thought about DIYing one with noctua fans (which I know are quiet, and
I have plenty of them in my PCs), but I suspect they're not going to be very
effective.

~~~
qpiox
It depends on what noise level is acceptable for you and the room size.

Out of 30 or so air purifiers available in shops here, of all the ones that
are in the $100-500 category, the Winix P/U450 are able to push the largest
amount of air under the constraint of <40db.

HEPA filters are rated at which air speed they are most effective and how much
pressure is needed. The ammount of pressure will only rise as the filter is
saturated with dirt. You need a sufficiently powerful fan, and fans that are
both powerful enough and quiet enough are very expensive.

~~~
leetbulb
I have two Winix HR1000. They have extremely powerful blowers and are quiet
when not in "turbo" mode. The turbo mode is actually pretty good for white
noise when sleeping. I've been running them 24/7 for years now and they are
still working great.

------
wiradikusuma
Do air purifiers really work? I always have impression they're just sham, or
at least placebo.

~~~
Eric_WVGG
I felt similarly, but I have a family member who is bed-bound, there’s some
asbestos removal going on, so I decided to take the plunge.

I can vouch for their ability to detect impure air. If I start cooking
anything, it switches on within seconds. It’ll turn on within about three
minutes of sweeping the floor. And if the detectors can turn on when the air
is dirty, it stands to reason that they can tell when the air is clean and
they turn off as well.

Shortly after getting this, some intriguing news surfaced regarding the
installation of air filters in a California school (due to a gas scare) which
resulted in a jump in test scores vs other schools in the same district.

I am not a scientist, but I’m feeling pretty convinced about the efficacy of
these things.

[https://www.vox.com/2020/1/8/21051869/indoor-air-
pollution-s...](https://www.vox.com/2020/1/8/21051869/indoor-air-pollution-
student-achievement)
[https://news.ycombinator.com/item?id=18219391](https://news.ycombinator.com/item?id=18219391)

~~~
Eric_WVGG
(A few minutes after posting this, morning rooftop construction started.
Sounds of saws and drills buzzing, large objects and beams being dropped
directly overhead. Air purifier just kicked into high gear. Yes, I’m
definitely into this thing.)

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

~~~
bradknowles
I’m a big fan of thewirecutter, and I reference them frequently on most things
I’m buying. But for HEPA air filters, I don’t feel like they test the models
that I feel are best for someone with asthma, or other similar breathing
problems.

We have several IQAir units, of at least a couple different models. None of
them have sensors to automatically ramp up the filtering when they detect
pollution, that would be nice. But according to the air quality sensors I have
in the house, they do an amazingly good job of filtering the air, at least if
you turn them up to high enough levels.

I have yet to see demonstrated clear benefit of the units with activated
charcoal filters for removing VOCs from the air, but my gut feeling is they do
help in those areas where VOCs are a concern. Not all parts of our house needs
that, however.

Having four furballs does greatly increase the dander and other allergens we
have to deal with, but we wouldn’t give them up for anything, so the IQAir
units at least make our lives a bit more livable. Especially during “Cedar
Fever” season.

------
jaclaz
Nice.

For some strange reasons it immediately reminded me of the scene in Apollo 13:

[https://www.imdb.com/title/tt0112384/quotes/qt0476826](https://www.imdb.com/title/tt0112384/quotes/qt0476826)

------
verdverm
I use a box fan with filters taped to each side. You want to do both sides or
the air gets pushed/pulled around the edges of the blades, rather than going
through the filters.

~~~
dredmorbius
That's doable, though you're increasing initial cost by about 1/3, and
doubling consumables, by using two filters.

The net effective increased filtration rate is marginal.

If you can afford this without concern, it's fine, but it's not necessary.

~~~
verdverm
It works with two and not with one, so pretty much required. The effect is far
from marginal in my setup. Also far cheaper then the post link, less than
half.

~~~
dredmorbius
Numerous documented and tested builds with only one.

[https://invidio.us/watch?v=kH5APw_SLUU](https://invidio.us/watch?v=kH5APw_SLUU)

YMMV.

~~~
verdverm
Cool, don't really care, happy with my double filtered setup

------
amluto
My general theory is that HEPA makes sense for filtration where a single pass
is all you get. So it makes sense for vacuum cleaners, air intakes, and such.
But, for room air cleaning, what matters is the _rate_ at which particles are
removed, not the cleanness of the air coming out. So, for recirculating,
something like a MERV 13 filter seems like a better choice: it lets more
particles through on each pass, but it also restricts airflow less.

~~~
dredmorbius
PM2.5 particles are small enough that they pass through many materials.

You can use lower-efficiency (higher effective particle-size) filters ... but
you'll just be blowing the bad stuff through them rather than removing it.

The net metric is _how fast the room particulate level drops_ , which is the
treatment goal. Flow rate is a red herring.

~~~
amluto
That’s why I suggested MERV 13 and not, say, MERV 8. If your filter removes a
mere 50% of particles at a given size but moves twice as much air as a HEPA
filter, you’re doing fine for a recirculating filter.

------
TaylorAlexander
I’m all for DIY, but this looks horribly underpowered to do anything against
major pollution.

I’ve got a Honeywell that’s $150 and it must have 20-40x the throughput of
this little thing.

[https://www.honeywellstore.com/store/products/honeywell-1700...](https://www.honeywellstore.com/store/products/honeywell-17000-s-quietcare-
permanent-true-hepa-air-purifier-germ-reduction.htm)

------
edgarvm
Has you tested it effectively can absorbe particles? It's a good project but
seems more like a nice form to waste energy

------
mundu_wa_hinya
Pretty cool project.... Except for the fact that I cannot buy any of the parts
from pccasegear. They deny certain geographical areas access to their website.
In fact, this seems to be the new normal. Last week, I was denied access to a
recipe from a .au website. Flipping on my VPN restores access..

------
cwkoss
I've always wondered if you could essentially hook a blower up to a bong to
filter particulates out of the air using water. Would be much cheaper to
replace the 'filter', but I suspect it wouldn't filter as well. Seems like it
could be an interesting tradeoff though.

~~~
dredmorbius
There is a set of "Luftwascher" ("Air washer") designs which effectively do
this.

These do filter out particulates, but also add enough humidity to the air that
this is billed as a feature of the system. In high-humidity conditions this is
less than ideal.

[https://venta-usa.com/product-category/airwashers/](https://venta-
usa.com/product-category/airwashers/)

------
grogenaut
Is a filter or an ionizer better for smoke?
[https://hackaday.com/2020/01/12/diy-ionizer-clears-the-
air-o...](https://hackaday.com/2020/01/12/diy-ionizer-clears-the-air-on-a-
budget/)

~~~
bipson
At least some of them don't really work at all.
[https://www.youtube.com/watch?v=VM9CJZpqfpA](https://www.youtube.com/watch?v=VM9CJZpqfpA)

With something as simple and effective as HEPA-filters, it seems unreasonable
to try other technologies.

------
Zardoz84
I would say that there are electronic schemes and plans to build DIY ion air
cleaners. They works nice to remove dust or tabacoo from air.

Also, ozone air purifier make wonders to keep at bay smells and fats
(wonderful to have on the kitchen), and kills bacterias, spores and fungus.

~~~
qpiox
Ozone is harmful.

~~~
unlinked_dll
It also smells bad too

~~~
regularfry
That's very subjective - I quite like the smell.

------
eeZah7Ux
Static pressure is important as well as airflow! Some info:

[https://www.engineersedge.com/filtration/hepa_filter_pressur...](https://www.engineersedge.com/filtration/hepa_filter_pressure_drop_considerations.htm)

------
ivanhoe
if you don't mind a noise you could buy a 2nd hand vacuum cleaner with a
built-in hepa or water filter (ideally also with adjustable speed to make it
less noisy) and just let it run without a hose, sucking the air and pushing it
through the filter...

~~~
adrianN
If you don't mind the noise and wasting a kilowatt on something that can be
done with two dozen watts.

~~~
ivanhoe
That kW will move you more air in 30 minutes than PC ventilator can in a whole
day, especially if you're trying to push it through hepa filter which is
fairly thick and adds quite a resistance.

------
SamBam
This basically looks like a mini Shop-Vac.

If you own a Shop-Vac (a wet-dry vacuum, generically), could you just turn it
on without the hose? It would draw much more power, but presumably would work
much quicker, and so may end up being more efficient.

~~~
OJFord
Of course; ditto any vacuum cleaner, AC with filtration, etc.

It's just airflow + filter, which is why DIYing them is so popular.

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htfu
Not sure what the point is when it costs $100 and is magnitudes smaller and
less powerful than a proper one which runs at $200-300 - an upfront cost which
is dwarfed in the long run by filter replacements, as would be the case here.

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blablaguy
there is also some other air filtering project on github. maybe a bit more
powerful but more expensive and definitely more ugly.
[https://github.com/KarstenSiemer/Open-
Airfilter](https://github.com/KarstenSiemer/Open-Airfilter)

I don't really think airfilters in that size so much. They need to push a
serious amount of air through the filters to be able to accommodate for
natural air circulation. Some pc fans don't do the trick I'd suspect

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CodeSheikh
OP: Do you think
[https://www.instructables.com/](https://www.instructables.com/) would have
been a better place for this than Github.com ?

Great effort!

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logfromblammo
Please don't use an iPhone X "for scale".

The dual-ruled calipers used in the next photo would be an acceptable
substitute for just using a plain old ruler.

~~~
jbob2000
Most people know what an iPhone X (or similar device) feels like. Not many
people have held calipers (or remember what holding them feels like) and not
many people can put into context what a marking on a ruler actually means.

For a quick scale judgment, a smartphone is perfect. It's not supposed to be
precise.

~~~
logfromblammo
I respectfully disagree. Smartphones do not come in a single standard size.
Using them as comparisons will end up with the same problem as using coins or
banknotes--it is only helpful for those already familiar with the specific
comparison item.

A "for scale" comparison is most useful with a metric-scale ruler. Metric
lengths are standard worldwide. Including an inch-scale ruler may help US-
based persons. The calipers were useful inasmuch as they had a metric length
scale etched into them--a ruler with extra bits.

By your argument, it is acceptable to report large lengths or areas in
multiples of US football fields, volumes as multiples of Olympic-size swimming
pools, or database sizes in multiples of the entire literary content of the US
Library of Congress. Journalists do this frequently, and every time, it drives
me absolutely bonkers (an aggravation level equivalent to 3 rush-hour traffic
jams).

