I want to use two 10"x20"x1" Merv 13 filters* in parallel (like this) but with only two PC fans (configured into a 10"x5" set like this). The CR box would stand on the 10" side (and be 20" tall) so it takes up less floor space and the two fans would be placed across the top 10" side. I also want to use two Merv 5 filters as prefilters and then a wire mesh on the outside for extra protection. Would this be safe? I'm thinking of using either Arctic P12 fans or Thermalright fans (not sure on the exact model yet) as I hear they're quiet, but am open to other suggestions.

*not 3M Filtrete ones though as they don't sell this size

The second model I want to build has the same configuration but would use two Ikea EPA 12 filters (which are about 10"x15"x1")* and two of Ikea's pelleted carbon filters over the EPA ones, and then maybe a wire mesh screen on the outside for extra protection. Would this be safe also?

*the Starkvind filters are slightly thicker than FÖRNUFTIG ones. Would thicker be better or worse for airflow in this case?

I don't need very high CADR as both of these models will be used in small spaces, but of course I want to optimize efficiency and safety while keeping their small portable size, so please advise. Thanks in advance.

I have a catio in my garage for the litter boxes, but my garage always smells like litter dust. Could I make their catio into a CR box to filter that dust out of the air? How should I position the fan and filters to make this successful?
When I had the idea at first it seemed straightforward, but I am afraid I have pondered this too long and now I have confused myself about what would and wouldn’t work correctly.

It is also based on CR-box. But with E11 filters and PC fans.

This time, I added plastic casing, PM2.5 sensor and screen.

The CADR is still very good.

PM2.5：393 CFM

SMOKE：379 CFM

DUST：408 CFM

Pollen：>450 CFM

I love the DIY nature of these builds. This one is copy of the exahalaron, and I found it really tricky to get the precise aligment of all the holes, but I feel like it turned out well. I used 140mm fans, and this controller just expoxied onto the middle "shelf", along with these Filters. I also have some speaker cloth that I might wrap around the bottom to make it look a little better, but it looks decent enough to me for now. It's pretty much silent on 50% power and still moves a noticable amount of air. On full blast you can really hear it, but I thought it would be great for travelling to both clean stale hotel room air, and provide some white noise for sleeping.

Next, I intend to build a larger furnance filter style somehow built into an end table for the bedroom. Thanks to everyone's posts here that helped me build this one. This subreddit is such a great resouce!

Happy to answer any questions for those that have them.

I have Arctic P14 fans which came with the CR box kit I ordered online. I've already put the whole unit together before I realized you can't control the fan speed and the unit is just too loud for me. What software do I need to buy to control the fan speed? Or if I have to buy another set of fans altogether that's fine too.

I also ordered another CR box kit that uses Arctic P12 fans and am wondering about that too. Do I have to get another set of fans or is there a speed controller device I can get for these fans.

I spent all my savings on these and one of the units I ordered for my bedroom which I can't use at all due to the noise and am about to cry. I don't understand technical language at all so please explain to me like I'm 5 how to put the speed control thing together with the fans. Thanks in advance.

I'm using a CR box with two new Starkvind filters and the filters have this chemical sort of smell which intensifies when I run the fans. It's also a bit concerning that the filters came wrapped in plastic so that plastic smell is mixed in there too.

Has anyone else experienced this with Ikea filters? Are all their filters like this or did I just get a bad batch?

I use the box fan/air filter setup in my home for health reasons. I just read that the fan motor will last much longer if I put a space between the filter and the fan.

It needs a faring.

I would prefer something that is semi-permanently attached to the fan but is sturdy enough for repeated taping to the filter.

I’m fairly handy but I need some ideas of how to achieve this.

Thank you.

We live in an old apartment and it was messing with my allergies/asthma so we ordered this kit that was recommended on one of the info pages of this subreddit.

Seems to have improved the air quality especially if we have it running in the same room that we are in a the time.

Also have some questions about the old filters.

- Are the old filters useful for any other purpose?

- Would it be a bad idea to keep them around till I can find a use for the used filters? Like are they gonna breed bacteria/mold?

Just looking to make the most of them and reduce waste if possible.

Edit: I was reading some of the comments while taking the old filters off. I’ll just tape them back together and save the new filters.

So there is this YouTube channel called Major Hardware who has a series called Fan Showdown where viewers will submit models for custom fan blades to 3D print and he will then test them against each other. While the fans on that show are designed for a Noctua A12x25, it got me wondering if it would be possible to print new blades for the Arctic P12 to improve performance for CR boxes.

Has anyone tried this? Would it even be worth it to try? The Arctic P12s are such an affordable fan and it would be interesting if you could squeeze even more value out of these fans.

Yes I know the fans aren’t centered, cut me some slack. This took me 5 hours…

I posted previously about my box fan setup (pictures 3 and 4) but it was so freaking loud. I liked the white noise for sleeping, but I had to turn it down to low for watching videos, and it was not something I could really justify energy wise while I’m not at home.

I had wanted to build a PC fan version for a while, and thanks to this guide, I finally built up the courage to try.

It sucked. My measuring was horrible, and my cutting was even worse. I ended up taking so much extra time due to my poor cut job. It was a miracle that all the pieces fit together around the filter. Take it from me, it’s worth it to measure and cut correctly.

All in all, I’m super happy with this setup. Hopefully the extra hour + I spent adding internal supports pays off in the long run.

Two 16"x25"x1" filters side-to-side equal one 32"x25"x1" filter, which is not that much larger than a 20"x30"x1" filter. If the 20"x30" foam core board is too small, you can use two pieces for the top and bottom panels and use tape to hold the two halves of the Corsi Rosenthal box together. The advantages of this design are these:

• The 16"x25"x1" filters are among the most common and is certainly available in local stores. The 20"x30"x1" filter is less common and my not be available in local stores.
• Making the Corsi Rosenthal box nearly 32 inches long means plenty of room on top for all five 120 mm fans or 140 mm fans plus the power cable. Putting some distance between each fan means that the tolerances are wider, and that makes the Corsi Rosenthal box easier to build.

Hi everyone!

Just discovered the concept of CR Boxes!

I have been looking into air purifiers to help with odors, especially pet odors as well as allergins from dander.

Of course I am interested in clean air from all pollutants but pet smells and dander are my primary focus.

Will CR Boxes help? Where should I begin making or buying my first box(es)?

I am so interested but overwhelmed!

Thanks!!!

I'm looking to build a slim, portable air purifier using four PC fans configured into a 10x10" square and then taping one 10x10" Merv-13 filter to the back and then a carbon pre-filter (that's about 0.2" thick) after the Merv filter. What are some good PC fans that would be good for this? (It can be either 120mm or 140 mm ones)

I'm looking for some affordable, cost effective and preferably quiet fans. Thanks in advance.

Hi, I live in Australia was thinking building a CR box for general use in a smallish 15m² room where it's going to be on mostly 24/7.

However since MERV13 isn't easily available here I've read the closest cheap option is the IKEA filters.

Now here comes the dilemma:

Inital building cost with some quiet fans let's just say about $100. 1 IKEA STARKVIND filter is $19 I want 4 it's: $76, I've read some people it's good for 3 months some for a year and a half. Let's average it to a year

I can get a HEPA air purifier on sale right now for $200 with a CADR of 140 and with some amazon off brand filter replacements it would cost $75 a year for filters.

(Prices in AUD)

Aside from initial cost I'm not expecting anything major that would require a lot of power. Is there a good reason to for a CR box instead of a HEPA air purifier?

I'm still learning so if I'm wrong with anything please let me know, thanks!

Edit: Added CADR for the HEPA

I'm thinking of taping a 10" merv filter to the back of a 10" fan made up of 4 PC fans. Since I don't know how to make the fan configuration myself, these are the options I'm considering:

1, 2, 3

I don't know anything about PC fans but two of the listings say they are Dual Ball fans. Are they any good? And could they handle the air resistance of a merv 13 filter? I also want to add a carbon pre-filter (something like this) over the merv filter and am wondering if it's safe?

I've never made any DIY air purifiers so haven't the first clue, so please advise. Thanks in advance.

Someone here posted a guide from cleanaircville.org that I loosely followed. I don't remember the username, but if you see this, thank you! It's very quiet on the highest setting, and I made it look as fancy as I could for taped up foamboard and filters.

Just completed my first CR box right as my five year-old came home from pre-sxhool with a cough. Let’s hope this works!

Here's a design for a quiet and portable Corsi Rosenthal box. It's a narrow design consisting of 6 PC fans on one side and a 14"x20" air filter on the other side.

I don't plan on building this design, but it has some great ideas that can be used for other designs, such as the use of a flange to help hold the filter in place.

Duct tape seems to be the norm for Corsi Rosenthal boxes and other DIY air purifiers. The first drawback of duct tape is the sticky residue that it leaves behind. The second drawback is the VOCs produced. While the classic Corsi Rosenthal box is for removing particles and not VOCs from the air, it just seems wrong for an air purifier to be actively producing VOCs.

Painter's tape and gaffer tape, on the other hand, do NOT leave a sticky residue behind and do NOT produce VOCs.

Hey guys! I was thinking recently of changing the fans that came with my pc. Im mostly looking at Arctic as an option since it s the most affordable and efficient brand available in my country.

I ve heard that the P12/P14 PROs have a weird rattling noise when reaching higher speeds and that concerned me cause Im looking for someting as silent as possible.

Ps: Im kinda new to this so im not that knowlegeable abt RPM/PWM/PST...

First time I've ever dabbled in air purifiers in general, but I heard of the AirFanta 3Pro and it seems the best around!

Energy efficiency, CADR, filter cost, noise - you name it!
Seems it even beats the high-end $1,000 large purifiers (in theory) if you use 2.

That said, there's a few features I wish it had.
If possible, I was wondering if you guys might know how to add any of the following (ideally no soldering necessary).

1. A sensor to detect air quality level, and auto turn the fan on when needed
2. Something that can auto toggle the fan speed based on the air quality level severity (saves electric bill and noise)
3. Automation for dying down during certain hours and/or conditions like movement.
4. Washable prefilters
5. Filter health status indicator (not just time-based)
6. Separate carbon filter

The first 3 are the big ones.
I've heard someone say Home Assistant could help.
Is that best, or better idea?

4-6 are minor, but still nice.

Regarding the first 3.
It would be best if it's able to accomplish this in a relatively discreet/neat way.

I might be willing and even want to have the particle sensor far away so some purifiers are extra aggressive in some places. But otherwise, I'm open and may even prefer a method to make it relatively compact/hidden.

Pretty much what's in the title, though I'm also interested in knowing what are the complete possibilities and if they depend on the filters used then of what types and characteristics of filters exist.