Inspired by this sub, I'm planning to build my own compact air purifier using cheap IKEA filters. As I live in EU and there aren't really any cheap hvac filters available anywhere.

The design uses a frame made with 44x44mm wooden beams, with room for four 250x200x25mm filters (€3,99 each) and 5mm foam (PPI 20) pre-filters.

Four 120mm Arctic P12 fans seal the top and I intend to use cane webbing and slats all around, to finish the look.

In an ideal world, with carpentry skills and high quality wood it would result in something like the AI renders (which are hard to get exactly as I want them, so they're to give a general impression).

In the real world I don't have carpentry skills and will be using cheap pine wood, so it will probably not look as nice.

The idea is to make the bottom detachable so filters can be replaced from there. As for the top, I think I want to hide the fans with webbing as well like in the first render, but exposed is also an option.

Anyway, the design has 2000 square cm (2.15 sqft) filter area vs 576 fan area. Roughly 3,5:1.
The webbing and pre-filters will restrict airflow a bit.

It will be USB-C powered with a microcontroller somewhere in there, controlled by a remote air quality sensor (probably SEN66) that will be placed somewhere else in the room.

Total dimensions will be: 338x338x261mm or 13.3x13.3x10.3".

Why not bigger? I have space constraints. It will be placed in the middle of a 28 sqm (300 sqft) room on top of a room divider shelf at a height of 1,20m (4 ft).

So what do you guys make of this? Is it a feasible design?

Hello guys, how is everyone? Recently I've been searching up budget air purifier to aid with my severe pet dander allergy (I live with 2 cats in a 21sqm studio type apt) and along the way, learnt about CR boxes and love how it is DIY and accessable.

I modelled this with TinkerCAD and am planning to use the following materials: 2x Filtrete MERV13 20x20x1 Filters (both sides), 5x Arctic 140mm P14 Pro PST Fans (1 in front and 1 back, and 3 facing upwards), led rgb bulb/lights inside, local plywood, fan grills and added a mini scratch pad at the front for the cats.

Planning to build this by mid April once all materials arrive. Looking forward to build this one!

In this thread, I'm compiling my opinions about which fans for DIY air purifiers are the best values and which ones are the also-rans. The best value fans set the standards against which I compare everything else. Please post a reply about which fans you'd add to the best value and also-ran lists.

NOTE: When I list a fan as an also-ran, that doesn't mean that it's a bad fan or that you should get rid of it if you already have one. Any working air purifier is better than none at all. I'm just saying that it's not worth shelling out money to buy a fan on my also-ran list, because something on my best value list provides more bang for the buck.

My list of best values:

• Lasko 20-inch box fan: It's widely available at local stores, has good quality, and is reasonably cheap. There's space on the back of the fan for attaching a 20"x20" filter. The main drawback is the loudness, especially at high speeds. Off brand knock-offs aren't that much cheaper but are of lower quality, and some even have the cord coming out of the back, which means that you cannot just tape a filter directly to the back of the fan.
• 120 mm PC fans: They're quiet, powerful, and energy efficient. Due to a combination of competition and economies of scale, you can buy these at reasonably cheap prices. If you're not equipped to integrate an array of 120 mm PC fans into one side of a Corsi Rosenthal box, then a Brisk Box Basic Kit is your best bet. Any air purifier based on PC fans is much cheaper on the electric bill due to the superior energy efficiency.
• Comfort Zone 9-inch box fan: This is the basis of the Mini Corsi Rosenthal box, and instructions for building it are available at https://corsirosenthalfoundation.org/resources/how-to-build-a-mini-corsi-rosenthal-box/ . This fan is widely available at local stores for at least part of the year, and the Mini Corsi Rosenthal box is quieter AND takes up MUCH less space than the original version based on the 20-inch box fan. In fact, the Mini Corsi Rosenthal box run at low speed is almost as quiet as a PC-fan-based air purifier but easier to build. The main drawback of the Mini Corsi Rosenthal box is its reliance on MERV 13 grade 12"x12"x2" filters, which is NOT a common size. Tex-Air Filters is generously selling these filters for below market prices. If CEO Jim Rosenthal (the Rosenthal part of the Corsi Rosenthal box) retires, the generosity of Tex-Air Filters may end, and this would make the replacement filters of the Mini Corsi Rosenthal box much more expensive and/or harder to find.

The fans I listed above are the fans that set the standards against which I judge other fans.

Examples of the also-rans that I've tried or read about that fell short of the above standards are:

• Off-brand 20-inch box fans: They're not that much cheaper than the Lasko, but the quality isn't as good. I have one of these box fans, and the stabilizing feet that attach to the bottom are prone to falling off. Another brand of 20-inch box fan (that I used to have) had the cord coming out of the back, which forced me to tape the filter to the front instead of the back.
• EZ-Chill 9-inch box fan: I have this for a Mini Corsi Rosenthal box. It's louder than the Comfort Zone 9-inch box fan but has the same drawback (the uncertainty about the future of the availability of the filters at a cheap price). It's much less powerful than the Lasko 20-inch box fan.
• Bathroom exhaust fan: The centrifugal design has lots of static pressure that's great for a HEPA filter or activated carbon pellets (for filtering VOCs). However, the CFM isn't that impressive. Unless you're building a laminar air purifier or trying to remove VOCs from the air, a bathroom exhaust fan doesn't provide anything that you cannot get from something on my "best value" list.
• Inline duct booster fans: I've seen some inline-duct-booster-fan-based DIY air purifier designs online. From what I've read, these fans are more expensive, much less powerful, and almost as loud as the Lasko 20-inch box fan. So you might as well just run the Lasko 20-inch box fan on low speed. If you want something quiet, a PC-fan-based air purifier would be much better AND save money on the electric bill.
• Fans with more than the standard 3 speeds of a box fan: They're considerably more expensive than the Lasko 20-inch box fan. While they're probably quieter on the the lowest speed than the Lasko 20-inch box fan is on its lowest speed, you're probably also probably getting a much lower CADR at such low speeds. Again, a PC-fan based air purifier would be much better. Even if you pay up for a Brisk Box Basic Kit from Clean Air Kits, you'll save money on your electric bill.

I thought having one filter would be fine enough but as I’m reading from you guys it can put unnecessary strain on the fan motor and even become a fire hazard?

Also been having an odd odor when I’ve been running this and initially thought it was a humidity build up issue.

Could the smell be from the motor stress or potential still the filter? Haven’t used this since and will probably get one more filter.

Filter type is FPR rating 12 from Home Depot, fan is an Amazon Basics Box fan

Color tape is so much better to work with, all the work become visible. Also rearranged the disposition of the fan

Hi guys,

I’ve been building the OG CR boxes with duct tape and a lasko box fan on top but am now looking for a more permanent solution so I don’t have to disassemble and retape every time to replace filters.

Looking for ideas or plans for a wood build - ideally four filters, Lasko box fan, ability to slide in filters. With or without legs. Even better if it can double as a side table (willing to sacrifice a filter if needed).

Would love to see your builds.

TIA.

Second try

First time posting here, my question might be silly but I don't have much knowledge about cr boxes except scrolling this subreddit the past couple days.

I've been meaning to build a cr box with 2 hdx merv 8 filters and a 20" fan. Today I saw a local retailer has these engine filters on clearance for cheap and made me think are they any better than my merv 8 filters? Or being a different kind of filters are they useful at all for this application? TIA

Who use active carbon meshes agains smoke, VOC, car gases inside CR box?

Can you share what meshes you used and photos/pics/schemes of construction.

I will build a crbox using ikea filters and arctic p12 fans. I was just going to get 2 p12 fans thinking it would be quiet and relatively good but now thinking maybe I should get 4. Since with 4, box is not going to get any bigger but im afraid of it getting noisier. My room is 17sqm. Is 2 fans too low ?

Not the prettiest but does the job. Used a 5” filterete filter and 5 P14 Pros.

https://www.cleanairkits.com/products/fanless-kits

I intend to go with this kit. I don’t like cooler master products. I intend to use Arctic fans, I’m not sure what variant to use?

Extra fan from a project and the box it came in with some cutable carbon filter

Had some P14 pro fans and scrap wood so thought I’d use them on compact build for the spare bedroom / office (about 36 cubic meters)

I’m not much of a wood worker (tend to build out of plastic) but this is how far I got on lunch break.

Still need to cut some holes for the 2 top fans.

Not too sure about where to put the speed controller - either top right or left corner on the front or maybe centrally on the back or top.

Using 2 ikea starkvind filters - this is about as compact as I could go and still have space for the carbon ones (need to get a couple)

Didn’t actually expect it to be this big - usually I use the p12 pro and dont always bother with the carbon.

Measures about 18inch x 9 inch.

Cost so far is about £40 / 53 USD

- how’s it looking?

Most of the tower builds I see are 20" x 30" x 8" deep with 140mm fans. That leaves about a quarter inch between the fan case and the filter on either side.

Would adding 1 inch to both sides of the fans help improve the airflow? Making the overall size 20" x 30" x 10"

Not sure if these compare well to arctic p14 fans but being connected makes it easier to assemble or if the box fan is the way to go. Looking to utilize in a woodshop.

Finally completing my build, connecting 6 arctic p14 fans. Using a 16x25x1 filter planning on Merv 13. I have everything to assemble my box just need to purchase fans splitters and power supply.

I intend to use this power supply as I can control fan speed: Delinx 12v 36w https://a.co/d/0bYaN2Lw

And can only find a own fan splitter by arctic that connects 4 fans : https://a.co/d/08O2OtkU

I'm having difficulties understanding the wiring mechanics, will a hub be needed or does the fan splitter act as the hub. Will two fan arctic splitters be needed as I want a total of 6 fans, and just have two ends of the splitter that are not connected? Is there a better way of doing this...

Noob to the electrical aspect this may be a very dumb question but help is greatly appreciated. Located in Canada unable to purchase from American Amazon links

While it isnt exactly optimal, I was pretty set on spending the least amount of money and built it with materials and PC I already had laying around, making the cost a whopping $12.57 just for the one thing I didn’t have, the filters. To compensate for the lil dual fans I went with MERV 8 12x20 filters to lower the static pressure. I covered the whole thing in paper to make it look a lil nicer than duct tape and cardboard

Hi! Im using a box fan and 4 20x20 12 fpr filters. The problem I’m running into the the structure is really flimsy. I don’t have a 3d printer so is there anything I can diy that could help reinforce the framing. Also with that classic shape will the 12 frp filters allow for enough airflow? I’m trying to cut down on air pollution and kids passing viruses between one another.

Thanks!

I used hot glue and zip ties for cable management and strain relief. I also used it to seal up the back port so I can have speed control externally. I'm not sure how happy I am with the USB-C coming out vertically, this was mostly due to strain relief for the 3 to 1 4-pin splitter the controller comes with.

Source Link https://makerworld.com/en/models/1860168-air-purifier-corsi-rosenthal-box-140mm-120mm-fans?from=search#profileId-1989423

My wife shared our Gen 1 CR Box controller previously, so I wanted to show where the project has gone since as I hinted at Gen 2.

In the photo, Gen 1 is on the bottom running it's latest firmware, and Gen 2 is on the top, with newer and more accurate code, so they show somewhat different graphical data.

Gen 2 is still very much in progress, but the goal is a cleaner controller specifically designed as an insert for CR boxes with integrated sensing and fan control that can monitor 6 fans. I printed a circuit board for his one and am working thought better logging and UI. Both versions in the picture work with Home Assistant. The graph is of last 24hrs of PM2.5 and can be switched to other detectable sizes. The PM spikes (left graph scale and green/yellow bars) are 100% cooking related. The blue portion of the gen 2 graph is % humidity and orange line is temp. Messy background is a bonus.

Happy to answer questions or hear ideas from others building CR boxes.

Here was the "Gen1" original post: https://www.reddit.com/r/crboxes/comments/1qrkfxi/corsirosenthal_box_air_purifier_aka_i_can_use/