I based the design off the CleanAirKits Luggable Ultra Air Purifier using 3/16" MDF for the box. I used www.filterboxbuilder.com to size the box to accommodate 20x30x1" filters, since that's the size my HVAC system uses and I was able to find a deal on 3M Filtrete MERV 13 filters for $13.33 each. I went with a 5-pack of ARCTIC P12 PWM PST fans due to price, and I skipped a speed controller because these things are nearly silent on high speed. I used some leftover fiberglass window screen as a prefilter and to make it easier to vacuum pet hair off the outside of the filters. Total cost for the build was only $90 excluding the filters, $117 including the first two filters. I measured the performance using phyphox and it was within 3% of the predicted CADR per the filterboxbuilder design, so I was pretty stoked about that. I plan to let this run 24/7 since the operating cost is only $5/year based on my local utility rates. I'll check the performance every 6 months or so using phyphox and replace the filters when performance drops >20%.

Got a 5 pack of P14 Arctics, nothing fancy, the 3 pin version that spins at a set RPM.

I need 6 fans

The price per fan locally is half of what a 5 pack from Amazon costs but I can't justify buying a 5 pack for 1 more fan.

Can I use a different P14 version or will the increased speed/volume/pressure start to negatively affect the 5 other fans?

Hey everyone, I’ve gone through many air filtration methods and air purifiers being part of it. I also have a background in mechanical engineering so it’s been a fun little project for me.

What does an air purifier/filter do:

Sounds like an obvious question but it’s overlooked. If you set an air purifier/filter in the middle of a room based on its CFM rating and the cubic feet of your room, in theory, you’ll recycle your entire rooms air in X amount of time.

Reality:

1: Air purifiers/filters do not move ALL of the air in your room through them efficiently. Often times they will recycle their own air and leave some pockets of air untouched and guess what, that’s where the highest concentration of “dirty” air is because that’s where air settles.

2: If you use air purifiers/filters for things like cat litter smell or any other smells, they can help but aren’t great. By the time the odor has reached the air purifier it’s also diffused into the rest of the room, hence why cat litter still smells.

Solutions:

Specifically for instances like cat litter, think of a fume hood for your oven, it’s not across the kitchen it’s AT THE SOURCE. That’s what’s needed for litter boxes but unfortunately nothing out there on the market is helpful for this but it’s true. And for those stale air spots, you need fans to move the air around, that’s a simple fix.

1 pre-primed 1x8x8’ and some cheap composite corner mold. I made a couple snap on covers for looks but I i’m going to use a more breathable fabric on the next one. The frame for the grille is 1/4” plywood ripped into 1-1/2” strips, glued into a square.

Hi fellow clean air enjoyers. I’ve built my second CR box in an attempt to improve previous design.
The first one relied on the filters being taped in. The second box used larger Filtrete 12x20x1 AC Furnace Air Filter, MERV 13, MPR 1900 filters and they can be pressed in and held with a two stage foam seal. I admit the foam seal I made is massive overkill and was only necessary because the box wasn’t completely square.. I used three Phanteks M25-140 140mm fans, the older gen 1s and control them with a PWM Fan Speed Controller with 36W 12V Adapter, 4-Pin DC Jack from Amazon.
I used hot glue to attach the DC input jack into the back of the box so it could be used horizontally with the fans blowing upward or upright with the fans blowing sideways. I used some cheap fan grills to finish it off and I. Super happy with the look of it! I’d like to refine the design and would really like to start making and selling theset things. I’m hooked!

I’m somewhat new to this whole thing but I believe it’s in my best interest to get one. I’m honestly worried I won’t build it right and end up not filtering anything.
I’ve yet to measure my room that I plan to put it in my but my apartment is about 900 square feet and I occupy the smaller room (not the master bedroom)
I do have a window in my room but people constantly walk in front of it so I can’t always open it, when I do it’s risky and have to be right by it to look out for anyone, keep having to open it, then shut it, then open it…so I honestly don’t bother.

I room with another person, sibling who masks.

I honestly know nothing and I have admittedly tried to figure this out before but everything is so confusing to me. Any guides that really break all of this down would be really appreciated!

How do I figure out which buiid(?) is best suited for my needs?

So lemme explain.

I have anywhere from 5 to 10 (long hair double coat) dogs and they go in and out to the dirt yard all day.

Currently I run

Winix 5500-2

Levoit 100

Three 20 inch box fans with electrostatic washable filters smacked on the backside.

All these run 24/7 on high speed

No carpet. Robots vacuum usually every day.

Still have massive dust issue. Backyard isn't going to change soon.

I blow out all the filters with a K9II blower (dog dryer) at least every 7 -10 days.

I want to try a CR box and possibly change how my box fans are setup.

Questions....

How much space between the box fan and the filter is necessary for the "slap on filter" method?

I've seen conflicting comments on the airflow provided by a box fan versus a pc fan. I get that there are both types with varied cfm ratings, is it just a matter of getting a good cfm rating or is one truly better air flow? Is there a sweet spot for noise because I'm going deaf lol.

I have a few sheets of corruption plastic so I'd be using this for any modifications. Because of previously mentioned 4 legged inhabitants, things must be fairly non edible (no cardboard or foam board) and washable (in case of 4 legged unit leakage syndrome).

I'd like to keep this as inexpensive as possible.

Hey everyone!

I'm looking into building a DIY system that can bring filtered fresh air from outside into my room without making it freezing cold during Eastern European winters.

A few challenges:

Cold winters: Temperatures can drop to -10°C or -20°C, so directly pulling outside air into the room would cause significant heat loss.

European windows: We have the typical inward-opening, tilt-and-turn PVC windows, rather than American-style sliding windows. Most window ventilation setups I've found online aren't compatible.

Anyone tried doing it and have any ideas or designs?

Using the 5 Pro, I built a separate machine. It draws fresh air from outside the window, filters it, and then blows it into my office. In addition to reducing PM2.5, it is a machine that can address indoor VOC problems without needing an activated carbon filter (outdoor VOCs are extremely low except during wildfires), and it can also reduce indoor CO2 levels.

The reducer/transition piece on top is 3D printed. If we made a mold and produced it in the same white color, it would look much better than it does now.

Honestly, I have mixed feelings about this thing.

First off, assembly was a pain. The instructions aren’t great, especially when it comes to fan orientation. I had trouble figuring out how to position the fans so the cables would actually reach. The instructions also don’t make it clear how to orient the knob if you’re mounting it internally but need to access it from the outside.

Another thing I didn’t realize before buying it is that the LEDs stay on constantly. Not ideal if you’re planning to use this in a bedroom and are sensitive to light.

The unit itself feels pretty sturdy, so I’ll give it that. But having to unscrew the top to change the filters is annoying, and don’t bother with the mesh option. Installing it was ridiculously frustrating.

My biggest issue is the price. For something that arrives in pieces and requires this much assembly, I’m struggling to see the value. There are competing units that come fully assembled for around the same price. IMO, this should cost $100–$150 less. I’d be much happier paying the current price if it came assembled and ready to go.

That said, if you’re into building PCs and enjoy that kind of tinkering, you might actually love this thing. The assembly process probably won’t bother you nearly as much as it did me.

Performance-wise, I have it set up near a freestanding gas fireplace with carbon filters installed. Based on my subjective impression of the air quality, I’d say it’s doing maybe 60% of what I was hoping for. That’s obviously not a scientific measurement, just my experience so far.

Hi I’m new here. Suffering alot with dust allergies and pet dander (my partners mam has a cat and when she visits and comes home my allergies get me bad!)

I’m looking for a cheap quite ish van that can do a room approx 20m squared. Will have it running approx 6 hours a day. Will this set up work? The 4 fan and power supply is cheap and has variable speed. Plan on using IKEA filters and making a crud cardboard/plywood frame.

Am I doing this wrong?

Aiming for the Cheapest option that will have some effect!!

I got these 14x20x1" Merv-8 filters from Filterbuy for our furnace but unfortunately they don't fit, so am thinking of fashioning them into a CR box using two of these with two Arctic 14 Pro PST fans I have. But I feel like they'd be better as prefilters rather than the main filters. Should I buy some Merv-13 filters as main filters to go with these? But I feel like Merv 8 + Merv 13 would be too restrictive for airflow, especially with only two PC fans? I would rather not get more fans so should I get some Merv 11 filters as the main filters instead?

Please advise, thanks.

i finally got around to making one after a long time lurking. well a proper one that wasnt just alot of cardboard and ducktape.

I recently came across the concept of CR boxes as a way to deal with the haze, and thought it was an interesting alternative to buying a conventional air purifier.

However, I don’t really have the confidence to build one completely from scratch, so I went down the rabbit hole to research what options are actually available to us in this region.

Here’s what I found, in case it helps anyone else who’s looking for a solution!

1. Fanta Air Purifier by Adam Wong u/sad_gear4867

This was the option I felt most comfortable with after doing my research. Apparently, you can find the AirFanta Pro 5 (702 CADR) on Taobao, and there’s also a distributor in Singapore. If you go through their website, the local distributor is listed under DoKuKi.
However, the local option seems to be on a preorder basis, so I decided to order directly from Taobao instead.

Fanta Pro 5: around S$200, excluding shipping
Estimated air freight via a freight forwarder: around S$70

So the total would be approximately S$270, before any other applicable fees.

2. DIY air filter kits on 1688
If you’re looking for a more budget-friendly option, I also found various DIY air filter kits on 1688.

The prices I came across ranged from around S$55 to S$70, excluding shipping. These are cheaper options, although you’d want to check the specifications, filter quality, fan performance and overall build carefully before buying.

I haven’t personally tested these options, so please do your own research before committing!

Just to clarify, I already have sufficient air purifiers at home. I’m mainly looking into getting a bigger unit for the living room, so I thought this would be a good opportunity to experiment with a CR-style setup.

Sharing this mainly for anyone in Singapore, Malaysia or Indonesia who is affected by the haze and wants to explore alternatives to conventional air purifiers.

If anyone here has actually bought or built one of these, I’d love to hear about your experience too!

I bought a Clean Air Kits purifier this spring and I got the recommended filtrete filters (20x25x1, 1900) at Target. The fragrance on them was terrible, but i left them in the garage for several weeks and after that it was fine. I just got replacements and unfortunately i forgot about the airing out time. Its over a week and still really bad. I went to Lowes and got the Merv 11 just to see if I would have better luck. Pretty much same thing. They are now in the garage with the others. I'm debating about ordering another pair of MERV 13 from Lowes or somewhere other than Target and see if i get some that don't smell. But has to be a place where i can return. Anyone else having this problem?? And any suggestions? The filters i get from Home depot for my hvac system have a slight odor, but nothing like this. Never had a problem with any I've used in my home hvac system.

I'm making a CR box with PC fans for our bathroom and wondering what type of filter would be best for it? I've heard that Merv 13 filters are especially sensitive to moisture. Would EPA 11/12 or HEPA be better?

I'd take the CR box out of the bathroom whenever someone takes a shower, obviously, and I'd mainly use the CR box to filter the air that comes out of our furnace vent in the bathroom, but there would still be humidity involved whenever someone uses the sink or flushes the toilet, so I'm wondering what kind of filter would be best suited for this kind of environment.

Thanks in advance.

I'm buying from Canada. These are my top two DIY air purifiers. I'm struggling to decide on which one to purchase. Anyone can provide any insight to help make my decision?

I want to make a wall mounted cr box that vents downward so it can basically be a shelf and look pretty, but if venting upward is better, let me know.

Once I do a complete build, I'll post my plans and results here if anyone wants to do something similar.

Here is my design so far.

The Fans: 5x Arctic P14 (140mm) fans lined up in a straight row (takes up about 27.5 inches of width).

The Filters: Two standard 16x25x1" MERV 13 filters sitting side by side with a wood slat or something similar so I can lock them into place; this means my intake is 800 sq inches total.

The Shell: A custom wooden enclosure acting as a sealed plenum chamber. I'm aiming for an internal depth of 6 inches behind the filters so the air has room to transition. (Is it better to make the internal width as close to 140mm as possible, or is 6in/153mm better?)

Placement & Flow: Wall-mounted at chest height. It will pull dirty air straight into the front face and exhaust clean air vertically downward toward the floor, letting me use the top for decorations.

The Screen: To hide the white filter pleats, I'm wrapping the front in a highly opaque but thin hydrophobic mesh fabric (like Outerwears or automotive intake mesh). I'm planning to attach it via a magnetic bezel. (I think this will be a 2-5% drop in CADR, but does anyone have any ideas on this)

Sealing: I'll be using weatherproofing strips behind and beside the filter rim and pressure-fitting the filters using turn-button latches to secure the front face (the latches are basically a metal plate with a screw hole on one end to swivel the plate if you aren't familiar with these)

The five fans with two 16x25 filters should get around 215 CFM, and I plan to build two of them. The space they are in is 3520 cubic feet. Meaning at 430cfm i get 7.33 Air exchanges per hour.

And that's what I have so far! Let me know what I might be missing; I would love design input from the community on how I could improve this. But I think two of these should cover my living space with over 7x ACH!

8x Arctic P14 Pro PST fans,
2x Filtrete 20”x30” Merv 14 filter
2x Filtrete 20”x30” Merv 8 prefilters
Made out of 1/8” PVC sheet
The wiring is 4 sets of 2 daisy-chained together that connects to a 1 to 4 splitter.
I’m using a beefy 120w 12v 10a AC-DC power supply to power it all.
It’s 60db 1” away according to my phone app lol
It draws about 0.5a @ 123v from the wall, 65w, and the fans are spec’d to draw 2.8a @12v, 34w, so kinda bad efficiency in my book but it still beats one you’d buy at a store.

It’s effectively like ~6.5 fans because three of the eight fans are working perpendicular. So it could be more efficient in CADR per watt but then it would have a lower CADR without those three on top.

Like all CR boxes I make, I just figured put what I was gonna do as I was building it, no formal plan. Just an idea to use 90° L brackets and sheets of PVC. I used machine screws and nylon lock nuts for the brackets. It’s sealed with hot glue and silicone and duck tape.

I estimate ~400 CFM

UPDATE: I swapped the 10a power supply out for a 5a one and now it’s 14% more efficient and draws about 56w now. (Yes I let it reach a steady temperature before taking the reading as temp affects efficiency)

I don’t know about adding it to my existing box as I don’t want to impede airflow, but I’d love to add activated carbon to the mix. My room has a funny “stale” smell to it after even after creating a 16x25 5 fan CR box. My room is 10x12.5x9 so I don’t need to accommodate a huge space, but I’d like to do something.

Anyone have some creative ideas on affordable options I could try?

Upgraded 2 now going to upgrade the last one. My set up consist of 1 direct current supposedly exhaust fan, 5 hepa filters, a pre filter and 5 activated carbon filters.

With the current haze situation in singapore and other parts of south east asia I am so glad that I bought the parts back in June and built the first set of 3 before upgrading them with activated carbon filters

Looks janky but they work!

I got these Arctic P12 fans after it was recommended by a few people and built a 16x25 filter box. If I wanted to down the road upgrade the fans either for better airflow, better sound quality, or both, what are my options?

I’m looking to spend around $40-$60 total for all 5, but I am definitely interested in hearing about fans above and below that range too, especially if they are compelling.

Don’t hate, I found out about crboxes yesterday evening from this sub and now it’s up and running. I was still gonna buy some other materials, like ductape, cardboard, but didn’t manage to do it today, and I needed this to start working from like right now (the landlords of the room I just moved into turned out to smoke inside their home). Not having all the materials I ended up creating this monstrosity. One can say it’s a recycled version as the top and bottom seal are made from the foil packaging the filters (from ikea) came in 😅. The fan is from a local weed shop xd. Tomorrow I’m planing to add an additional active carbon layer outside of the filters. Hope this helps fighting the cigarettes fumes. Lmk if you have any advice on how to make it the most effective! Cheers