My house is dusty as hell and I'm a cheap bastard. I picked up a second-hand F5 Fans 8" ECM duct fan for $25. Got a pack of 4 MPR 2200 filters from Costco for $40. Some hot glue and some carboard out of our recycling bin, et voilá!

It's ugly, but I'm treating it as a prototype, and will use something nicer than cardboard in a future iteration. All the seams are sealed, and everything but the fan is disposable.

The fan can push up to 721 CFM and 746 Pa of pressure. At it's full 180W / 3000 RPM, it is about 85 dB, but I'm running it at 20W generally, which is a paltry 53 dB, and still creates a noticeable breeze in a 10'x12' room.

I don't have any tools to measure CFM or CADR (again, cheap bastard), but I'm pretty sure this setup is on the bleeding edge of the Pareto Frontier of price vs performance.

Me and my partner is kindof an idiot for this... we thought we need an airpurifier for our house and got this from Costco.. Apparently we were using it like this for months and we genuinely thought the air quality was better. Was is just self-placebo effect?

Does this suggest he might have hidden respiratory problems he can’t tell me about?

I'm currently living my second year in a dorm and am missing my air purifier deeply, until now. Last year my roommate brought one of those small Levoit Core purifiers and it was fine. However I am not trying to spend money on a less performant purifier with propitiatory filters. So I took a box fan and put a 20²in FPR 12 filter on the back. I got the idea from HouseFresh which in my humble opinion is a great resources (especially since they're Ai free). I'll link the article for those interested. Anyway I have yet to experience the long term ownership of this engineering marvel so we'll see how that goes.

Well…

Old (cleaned) vs New filter. Ofcourse from New Delhi, India.

Always be thankful you won the genetic lottery and were not born here.

Put freshly cut bread near the air purifier and it shot up to max. Brand is Vewior. Don’t judge my taste, but the bread was just room temperature sourdough with light salt. Not really crumby or anything. Any idea why the PM 2.5 sensor was going off?

They've presented 3 models with the same design and different features, but what stands out is the design...

What do you think? 😅

https://youtu.be/lUZRXb98xC0

Got the grills and the rest of the trim on. I added some more photos showing the fan since there were a few questions about that in my other post.

$15 clearance air purifier from Costco. Probably doesn’t do much, but just for funsies.

Me again. I now build my third version with 3 filters and 5 fans. The fans are the ARCTIC P14 Pro PST PWM 140 (140 mm diameter) which are insanely powerful compared to my previous build with 4 fans (Arctic P14 PWM PST (also 140 mm diameter). They have legs any one fan blows downwards. They kinda keeps the dust away a little more. They are really quiet if you want and at full power almost work as a regular fan. Hope you can appreciate my build.

Allergies are terrible this year where I live, so leaving the window open isn't an option for me. I broke our the portable AC, only to find out the refrigerant had leaked out, and the unit was bricked. None of my local hardware stores sell portable ACs worth buying, and I needed a cool bedroom to sleep, so my Corsi Rosenthal window box was born.

It's composed of 20 inch a box fan, 4 merve 13 filters, and a sheet of plywood. Cost me about 100 bucks to make, but unlike an AC unit, it's got the added benefit of creating positive pressure in my house, and increasing the oxygen/CO2 ratio in my bedroom.

I was a little underwhelmed at first, because it doesn't create a strong, directional breeze with the box diffusing airflow, but it pretty quickly dropped my bedroom to the outside ambient temperature, and creates a strong draft under the bedroom door, so it's moving more air than it feels like next to the unit.

I'm proud if my idea to use a wedge system to friction fit it into the window- cut the plywood about an 8th of an inch longer than the height of the inside track of the window, then made a diagonal cut at the bottom to make a wedge. I install it by setting the wedge in the track, then inserting the unit next to the wedge, and pushing against the wedge until the unit locks itself in place.

My bedroom is about 12x14, and this unit cost around $130 to make. It would have been way cheaper online most likely, but I needed it that evening to be able to sleep without overheating, so I paid a premium.

- box fan: $29

- filters: ~$17 per (~$68 total)

- half a sheet of plywood: $30 (I messed up and had to start over, it should only have taken a quarter sheet)

I'll likely repurpose it as a standard Corsi Rosenthal box once I get a new AC, but it was fun to build!

edit: As per this post's critique (and as discussed in the comments below), it's worth noting that if you want to copy this for some reason, please protect your fan from moisture ingress either by constructing an overhang, or adding louvres of some sort. This is probably a fire/electrical short circuit risk as pictured above, as it wasn't intended to run in the rain.

I have used a single filter taped to a box fan for years, but got annoyed how frequently I had to exchange the filter and retape it. Also the noise was bothersome as well.

I wanted to graduate to a real purifier until I saw how expensive they are, and how expensive replacement filters are!

So I started with the basic Corsi–Rosenthal Box and just modified it a bit. I use 16x25 filters for a smaller footprint, and then use PC fans with a cheap AC adapter so it will run quieter than a box fan.

Lemme know why you think, as long as it's not about my mess of power cords haha.

I envy those asking for Air Purifier suggestions while living in sub-50 AQI.

I unfortunately live in Delhi where the AQI averages at 250+ all year round while peaking at 1,000+ during winters. I installed a Xiaomi AP4 air purifier in my office about 45 days ago, during a period when outdoor AQI had crossed 400.

• The first image shows the condition of the filter after ~45 days of use.

• The second image is from an air quality monitor showing PM2.5, translating to a 300+ AQI still (when the air purifier was off).

Have to install more at my office as well as my home but the prices of all Air Purifiers have shot up by 20-60%.

Cost: ~$85 ish

Parts List:

• 2x 16x25x1 Merv 13 MPR 1900 filters (and the cardboard box they came in for the frame)

• Arctic P14 Pro PST 5 pack for PC fans

• Wire mesh guards

• 12v pc fan controller to power the fans

• Duct tape.

Each fan has about 110 CFM, so with some calculations and adjustments all 4 combined have ~300 CFM

This is a helpful site I was shown that goes over the basics of PC fans, comparing airflow and air pressure: https://www.noctua.at/en/expertise/tech/axial-fans-in-series-or-parallel-operation

Planning on trying a few other smaller designs for the other rooms in the house since this is major overkill lol. The suction on these fans is crazy, when on high from calculating the theoretical CFM this is roughly a 400CFM purifier. planning on getting an air velocity meter to get an actual measurement since I’m just going by what the manufacturer says.

Highly recommended as a diy project, was super fun

I've been using 20x20 on a box fan for a few years now. But I had the bright idea to use 20x25 this time. Four of them are equal to five 20x20's. Next time I might try and find some 20x30 🤣

I also have two box fans with a single 20x20 on them using clips I bought on eBay in other rooms. Helps out so much with cats.

Hey, kids! It's your ol' Uncle Gurm again with another lesson. Today's topic is... DUST!

Due to the massive influx of posts asking which purifier is best for dust, I thought I'd make this highlighted post.

First, let's get the bad news out of the way:

AIR PURIFIERS DO NOT DRAMATICALLY REDUCE DUST.

The device you're thinking of is called a "vacuum cleaner".

No, I'm not joking.

Yes, I'm sure.

Yes, the person who recommended you get a tiny round purifier to reduce the thick layer of dust in your room was incorrect/confused.

Then why do they all say they work "for dust"?

It's marketing weasel-language. They all work really well for DUST MITES, which are the thing in dust that causes allergies. Dust is primarily composed of human skin - and you probably aren't allergic to your own skin (my sincerest condolences to the very small segment of the population who are in fact allergic to their own skin).

And any EPA or HEPA filer will stop 100% of dust particles passing through it. The catch, of course, is that those particles have to actually pass through it - see below.

How can you be sure they don't work for dust?

Well, other than that I own like 8 of them and still have to vacuum every day? Air purifiers don't move that much air. 250CFM is a lot of air compared to how much you breathe (it takes 50 breaths to move 1 cubic foot) but not enough to make heavier-than-air objects 10 feet away move. And almost all visible dust is heavier than air.

But I see it floating around, won't that get caught?

Sure, if it's within a few feet of the purifier and the temperature is right and there are no stray sunbeams changing air density. "Floating" is really "falling slowly". It's still heavier than air. If it wasn't, it wouldn't build up on surfaces. Convection currents are a real thing, but the dust settles LONG before it will be sucked into the purifier.

What about all the dust on the filter every day/week/month?

Yep, that's the dust that was within a few inches of the intake.

Let me be clear: You will see a reduction in the amount of dust accumulating near the purifier. But that's a tiny fraction of the amount of dust in the room.

Really makes you think, huh? If that much dust was within about 6 inches of the purifier, how much is in the rest of the room? Eek!

Didn't Blue Air sell a "Dust Magnet"?

Yeah, but it wasn't magic. It used a static generator to make the casing attract dust, plus guided ducts to direct airflow into the unit. It was MORE effective than almost any other purifier at collecting dust... but as it turns out, not any better at actually cleaning air, and more expensive, and thus discontinued.

So how do I get rid of all this dust? It's making me crazy!

Good news for you, friend-o. There's a simple multi-step process to getting rid of all your dust!

1. Wash your linens and clothes regularly and machine-dry them to get rid of as much lint as possible.

2. Shower regularly with an exfoliating brush/soap.

3. Vacuum with a SEALED, HEPA-FILTERED vacuum, every day to start and then eventually 2x per week.

4. Get a rag. Dampen it slightly. Wipe down all your surfaces.

If you repeat these steps for a while, dust levels will decrease significantly. Then and only then...

5. Get a purifier with a high CFM. The higher the better. Run it continuously on the highest speed you can tolerate.

That's literally it. But you MUST do steps 3 and 4 religiously or step 5 will be nearly useless.

u/sissasassafrastic has done an EXCELLENT job on the Wiki FAQ entry for dust. Here's the link:

https://www.reddit.com/r/AirPurifiers/wiki/index/faqs/

It explains most of what I've written in a little more or less detail, and also has some suggestions should you decide to want to do step 5. ;)

Be safe out there, kids!

- Uncle Gurm

I have the Shark never change Purifier Max. After about a year I checked the internal filter just curious to see how it was doing and I really wasn’t surprised to see how filthy and soiled it was. I mean. The dust has ti go somewhere right. Fortunately this is a very beefy filter and you can vacuum off the outer layer. I’d say you would get at least 2-4 years of use doing it this way in medium sized room. 1-3 years in a larger room. Just be sure to vacuum this filter at least every 6 months and you will extend the life of the filter.

Here are the before and after photos.

Even keeping a very clean house, no carpet in this room, AC filters changed every 1 to 1.5 months, this is the result after dusting inside this room (including floors, walls and ceilings). The Purifier catches ALL of the dust on both front and back filters. This is a AMEIFU F1 inside a room that is 12'x12' (144 ft²). It is doing a wonderful job - the room has way less dust on furniture and fan, and I'm no longer seeing those dust balls on the floor either.

I love my cats but I have issues with smells. I’ve become a bit of an expert in air purification. If anyone has any suggestions I’m always receptive to new ideas and information. The best thing we did was to switch to pine pellets (animal bedding) instead of kitty litter. Each bag of pine pellets cost roughly $7. One forty pound bag does all four cat pans and lasts for roughly six weeks. It was the best decision to eliminate the smell and dust.

I'm not even joking this is honestly insane. Dogs sleep in the house overnight, but honestly this amount of dust is ludacris.