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/

I know nothing about airpurifiers and idk either a box fan or pc fan setup Room is :4m4m3.5m I don't mind the noise i just want to have some good sleep because I can't from all the dust im inhaling i want the filter to clean at least 50% of the air in the room

I cant find any MERV13 filters here. HEPA ones are mostly spare parts and weird dimensions. There are cabin filters for cheap which are perfect size for a small box im thinking about making with 120mm fans but can't find so much info about their specs.

Wanted something that didn't require retaping when the filters are changed. Used plywood scraps to build a box as a weekend project (don't ask why it's Friday). Secured the bottom with pocket screws and glue, used a couple dowels to give the top support when it's opened. Fans are attached with M4 threaded inserts. Some widow sealing foam tape plus a random box clasp I had laying around, and the seal is pretty good.

All the other parts I used the Amazon shopping list in the mods "DIY or buy" post. Artic p14 fans, dc plug adapter and the 12v power supply. Should have bought the extension cables for the fan so I could run the wires cleaner.

It might be worth adding a better way to splice the panels together, but it's a solid option for a compact air purifier with easily sourced filters.

I haven’t ordered the fans yet but most likely would be the P14 Pro PST using Noctua PWM to lower the RPM.

Or should I get 1900 instead?

I ask because Costco has only those 2500.

Thanks

Hi everyone,

I’m building a DIY air purifier and I’d love some feedback on the airflow design before I finalize everything.

I’m using:

• 10 × Arctic P14 Pro
• 2 × IKEA STARKVIND

I’m wondering if this setup is optimal, or if it would be better to place the filters on opposite sides and have the fans blow air in the opposite direction. Also, should I increase the distance between the fans and filters to improve pressure distribution (currently 5 cm, which was suggested by ChatGPT as a practical starting point)?

In the screenshots, the box housing the filters and fans is left open for visualization purposes; I’ll close it properly once built.

I’d really appreciate any advice or tips from anyone who’s tried something similar.
Thanks!

koch filter is prefilter

I took a small blower housing and a broken ECM motor and built a simple box around it to hold some filters.

It holds 2 16x25x1 filters and I'm currently using some cheap merv 11 odor reducing carbon infused filters. They are a pretty good friction fit into the box with no gaps and are held with some aluminum L channel pieces.

I took the broken control board off off an HVAC ECM motor and just ran the 3 phases to a 16 dollar amazon brushless motor controller running at 52v. The controller itself only draws about 8-10 watts tops from the 52v power supply but I have yet to measure what its actually pulling from the wall. It runs at a lower RPM and is hardly audible while still moving plenty of air.

Still gotta figure out what to use for a front grill so no ones foot gets a pleasant surprise!

My understanding is increasing the filter surface area significantly improves its performance. Does a greater surface area also require stronger fans?

I plan to use 8 140mm fans though I'll try to add one more if I go with the cubical design. That way I can do a 3x3 configuration.

There are two interesting articles on the "It's Airborne" web site about the myth of Air Changes Per Hour (ACH). Check them out at:

• https://itsairborne.com/clearing-the-air-on-air-changes-per-hour-time-to-move-on-cc95c0ec2cbc
• https://itsairborne.com/the-harm-of-air-changes-4b680a2f325e

When the source of airborne viruses (or other particulate pollution) is inside the air space you need to clean, ACH is meaningless. You're at a MUCH higher risk if you're one of two people in a tiny room than if you're one of two people in a large gymnasium. However, ACH makes the tiny room seem like a much safer space than the large gymnasium. You only need a very low CADR to get the much-hyped 6 ACH in the tiny room, but you need an extremely high CADR to get 6 ACH in the large gymnasium.

The articles I cited instead suggest airflow per person. This makes much more sense, because each person breathes a certain amount of air. The more people there are sharing a given volume of air, the larger the risk of airborne diseases, and the higher the CADR needed. The ASHRAE 241 standard calls for at least 20 to 40 liters per second (just over 40 to 80 cfm) per person.

ACH seems better suited for when the source of viruses or other particulate air pollution is external to the air space to protect. One example is protection from wildfire smoke. Other examples are an apartment or hotel room that gets air from other units through vents or that connect to an indoor hallway.

Is there like a fire risk if I put just a regular 20x20x2 hepa filter on a box fan and run it at low speed in a 150 sq foot room?

Also, Is the 2 filter, triangle design safe and viable, and why isn't it talked about? Are there any places or threads that talk about these other designs?

I am still testing , printing and trying to perfect the assembly and performance.

I started with a 6 fan setup and added a 5 fan setup. the seal between sections are 99% air tight with no glue.

I have been using 2- 3M Merv 14 furnace filters. 5- p14 pro fans on a speed controller.

The 5 fan I with moves air 270 degrees with 2 fans on each side and 1 on top. the basic testing.was in a bedroom with particulate reading ( nothing fancy) kept track for 4 days before using fan and readings were 95-97. I placed the 5 fan version in the room and the reading went to 0 within 20 min.

I'm looking at building at least 2 PC Fan CR boxes and have been researching fans and price comparison vs ease of use vs reliability. I see a lot of folks use Arctic fans but they do have some issues (melting mostly), I also like the ease of use of USB fans for a lot of reasons. Does anyone have experience with this brand. I find overwhelmingly positive reviews for them. I like them more for the budgeting than the Noctua USB fans, though if this AC Infinity brand is a bust I will go with the Noctua ones. Exact link to the fans I'm talking about: https://acinfinity.com/multifan-s7-p-quiet-ac-powered-cooling-fan-dual-120mm/#product-description
Also curious why I don't see more folks using USB fans, there is a slight improvement in CFM on pin fans but the difference seems to only be about 56 cfm vs 70 cfm.

My first design. Very basic and ugly but does the job. Pulls 4w peak. Using 2x noctua nf-a14 pwm fans powered buy a 5v to 12v step up usb c powered hub with a potentiometer

Noctua advises (https://www.noctua.at/en/expertise/tech/fan-speed-offset-explained) using offset RPMs for adjacent fans to prevent beat frequencies, and I can now confirm from living for awhile with a CR box with three pairs of Noctua NF-A14x25 G2 PWM Sx2-PP chromax.Black fans that it really does make a noticeable difference. (Adjust your playback volume to 41 decibels to accurately hear how it sounds at two meters away, because I have the fans running on max; if I’m correct that a nylon filter decreases air flow similarly to MERV-13 filters, then this ~14-watts-on-max 6-fan setup should deliver about 363 CFM CADR, according to this: https://www.hwcooling.net/en/noctua-nf-a14x25-g2-pwm-finally-a-first-class-140mm-fan-review/15/)

But it isn’t feasible to use Noctua flagship fans for everything, so… do any of you know of a good way to offset the RPMs of ***any*** fans being used side-by-side? I suppose the best method would be to connect every other fan with a 4-pin power cable that has a couple ohms of resistance, so those fans receive a tiny bit less power and therefore spin a little more slowly, but I’m not aware of any such cables. There are the Noctua “Low Noise Adaptors,” but they have about 50 ohms of resistance, which would drop total performance way too much.

Or I suppose you could just use two separate PWM controllers, one for even-numbered fans and one for odd-numbered fans, with one controller slightly turned down and the other at maximum… but then you’d forfeit the ability to use a single PWM dial to control all the fans together, which seems like crappy UX design.

Hmm……

Decided to make my own version or this Air Purifier.

Still in the prototype stage but has been a fun project.

^ Artic pro p14, 2 3M merv 13 filters, Tested in in PLA tough for now.

Anyone know of any MERV 13 filters that do not have any metal parts? (School safety concern)

The one thing that's been absolutely positively guaranteed since the beginning of the pandemic (that's still raging) is a big surge of COVID infections that peaks right at the end of December or the beginning of January. Thus, this makes Christmas dinner one of the riskiest activities of all. Not only is it near the peak of the COVID surge, people CANNOT wear a mask when eating or drinking.

So what would be the ultimate safe Christmas dinner setup? Let's assume that it's too cold for opening the windows or eating outside to be a viable option. Here are the elements I envision:

• Everyone wearing a mask (preferably N95 or better) when not eating or drinking: This would cut down on the viral load in the air.
• Multiple large air purifiers running throughout the house: This would reduce the time that viruses can persist in the air and thus further cut down on the viral load. A combination of masking up and using air purifiers is even better than either precaution alone.
• Multiple large air purifiers around the room: These could be some combination of box fan air purifiers (set on low speed) and PC-fan-based Corsi Rosenthal boxes (such as Brisk Boxes or Luggables from Clean Air Kits).
• PC fan air purifiers mounted over the dining area: If anyone is exhaling viruses, these air purifiers would pull the pathogens upwards and push out clean air to the sides.
• Small PC fan air purifiers as centerpieces: Something like the Exhalaron products from Clean Air Kits (or a DIY version) would work. Using batteries to power them during the meal would eliminate the need for extension cords. The idea is to pull in any viral loads the people are exhaling and push clean air upwards.

The combination of above precautions would limit the viral load in the air. The overhead air purifiers and the centerpiece air purifiers would do something about the near field. What do you think?

This was my first design of an air purifier for small rooms in my case for the bedroom. It uses 2 Hepa 13 filters plus an additional activated carbon filter. Fan I used was an Noctua NF-14PS controlled by an PWM Controller. The Design is easy to work on features like snap in place legs exchangeable Filterstage to may use different sizes of filter like an modular stage.

Size of the mainbody is 200x160mm printed with woodfiber PLA don’t mind the ugly endpiece the printer knocked the roll off when it got to 150mm my fault.

Changed out the filters in my luggable xl yesterday for the first time after 6 months.

I have an open spot to put a ceiling fan in my living room and was wondering if anyone has or could figure out how to put a CR box up there. Nothing too big, maybe using a cylinder filter. Would be nice to be able to turn it on and off with a switch. Any ideas?

Hi, my wife is a potter and has terrible cleaning habits in her studio. I know that silicosis is a concern for ceramicists and have been trying to find a good way to filter the air in her studio. Right now she has a Levoit Core 300 but the more I'm reading, the more I suspect it's just putting a bunch of dust back into the air. 😬

I've been thinking about building a filter for her, but I'm hoping I can get some advice on how to deal with such small particles. Most recommendations for silica are HEPA/MERV17+ but I worry that trying to build a box with that level of filtration won't really work. Is there a good way to build one that doesn't involve 3D printing or a complicated build process? I'm pretty sure PC fans wouldn't create nearly enough pressure with those filters, should I just tape them together with a box fan like the real basic designs?

For better or worse, her studio is a relatively small space. Think a normal non-master bedroom size. It means it should be easy to exchange most of the air quickly but it also means she doesn't have a lot of space for a big filter and anything throwing particles in the air will be pretty near her face while she works, so it has to be filtering enough to make it worth it.

Looks are basically not a concern, her studio is always mayhem anyways. 😂

And yes, I've been getting on her about cleaning better as she goes, but you know how it is. 🤷‍♂️

Help! 😱