We all use airfilters at home for our hvac system which needs replacement every 60/90 days. 60%-70% of that air filter is the mesh that supports the filter paper and the cardboard paper that supports the structure. I am designing a frame that can be reused by only replacing the filter paper.
I know there are a few products in the market but I am designing something much better in terms quality.

What are your holistic thoughts on this idea?

I downsized my homelab foot print and pc cooling requirements and now I have a bunch of 120mm Noctua NF-F12 iPPC-3000 PWM fans. These things move a lot of air but damn they sound like a jet engine above 50%. So I'm thinking of setting up some kind of controller and automation.

For example my office box could run 100% from 6pm-7am, and 30-40% during the in-office time. Sprinkle in a little automated magic if im working early or later i could set something up to wait 10-30 min before going into full speed.

My idea that started me going down this rabbit hole was thinking it would be cool to have all boxes run at 100% when no one is home or kick the speed up if no one is in the room.

Im still looking into controller(s) and sensor types, but wanted to post to see if anyone else has done anything crazy like this before.

I bought 4x 20x20x1 3m MERV13 filters and a Lasko 20 inch box fan but the fan got canceled because out of stock. My guide I read only really mentioned lasko and utilitech for fans. Does the brand really matter or is there any I should avoid?

I made my first Corsi-Rosenthal box for just under $80! This is for home use. We’ve never had an air purifier, so I’m looking forward to seeing if I can tell any difference. A few questions if anyone has insight/recommendations:

1) Were 1” filters okay? I used the Filtrete 1900 MERV 13 filters that most forums/sites recommended. I couldn’t find the 2” Filtrete filters.

2) Costco had Filtrete 2500 MERV 14 1” filters ($35 for 4 on sale), but I had read some forums saying those could put too much pressure on the fan motor? Is that true? Or would those be okay to use in the future?

3) Is it recommended to run this constantly or how many hours per day is recommended? I was thinking I’d hook it up to a smart timer and have it run periodically during times when we are home.

4) We have an indoor wood burning fireplace that we use occasionally in the winter months for special occasions. I know burning fires indoors has a negative effect on indoor air quality. Will the CR box help offset some of the impact of those indoor fires in a meaningful way?

Cheers and happy breathing to all!

Hi everyone,

I'm in Germany, where bag filters (pocket filters, 592x592x600 mm, F8/F9 ≈ ePM1 65-90 %) are cheaper than the compact filter panels typically used for Corsi-Rosenthal boxes. Because of their large surface area they should have a low pressure drop at moderate airflow.

My idea: one box with a single bag filter (592x592x600, 8-12 pockets) on one side and Arctic P12 Pro or P14 Pro PC fans on the other side, running at around 25 dB.
i would built the box so it would sit horizontally and the airflow would also be horizontal. I would position the bag filters so that they are vertical. This way the bags wouldn't hang.

Questions:

Has anyone built something similar? Will PC fans deliver enough static pressure through a deep bag filter at low RPM? I saw that the Artic p12 pro has the best pressure values for the artic fans.

Any flaws in the design (sealing, airflow distribution, fan placement)?

Does anyone have real pressure drop data for bag filters at low airflow (200-300 m³/h instead of the rated 3400 m³/h), i could not really find any reliable data?

Thanks!

( Sorry for the weird AI Image , but i think you'll get the point how its meant to be built/look)

I live in one of the most polluted cities of India and was planning to build my own purifier for a long time before the winter mayhem starts. Here is how I built it -

Fan - 220mm backward curved centrifugal fan. 230V - 50Hz. 441 CFM of free airflow and cutoff pressure of 1.8inch H2O.

Filters - 24x12x2 inches H13 aluminium hepa filter. 24x12x0.32 inches MERV 8 aluminium pre filter.

Box material - 0.75 inches thick plywood. Took a carpenter’s help here. It has turned out be heavier than I expected. Planning to attach wheels to the base.

Sealant - Silicone and wood putty in some places.

Tapes - Aluminium tape, standard electric tape, high density foam tape (to create a gasket).

Miscellaneous - Connecting wires, linear regulator, 3 pin plug top, clamps for fan.

Images - air purifier, noise levels at a distance of 1.5m(only purifier running/completely silent room/only ceiling fan running), before and after of a room filled with incense stick smoke.

Room size where it was tested - 8ft x 7ft and 10ft ceiling height. The pictures are taken 20 minutes apart with fan running at lowest speed for 15 minutes and at highest speed for 5 minutes.

Total cost - About 11,000 rupees. ($110)

I'm building a cr box and it's not built yet. But I've got the fan and a single filter going right now. And I'd like to test the quality of the air. And see it's fluctuate thought day and how fast it rises and falls with different methods. Is there a device for this?

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?

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%.

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.

I'm sure others have also said this, but I didn't see it and got nailed. First of all, their filter efficiency is not as claimed, which is core. This is reported at this website, but also I tested a CR box made with them and indeed this appears to be true as the flow rate to CADR ratio does not add up, and no it's not my measurement method as I have measured many CR boxes many times. I have all the equipment and skills to do that, I bet they didn't expect that. Obviously I should tell people.

But then, even worse when I asked for a refund they are now refusing and wasting my time throwing AI customer support reps at me. This is through amazon, too. Clearly they are one of those companies that unethically tries to hustle everyone.

The filters even had leaks around the edges, which may be part of the reason their efficiency is so low, however I doubt that is the whole problem. Pics attached. 3 of the 6 filters they sent me have this problem, one has a pretty large gap where the folding did not go quite right during manufacture. I didn't use that one in the CR box, so it is not a factor in the measurements I took even.

Website that caught them with poor filter efficiency: https://filterstudy.com/filterbuy-merv13-platinum-furnace-filter-review-20x25x4/

They are extremely prominent in search results for filters, so it is all the more important that people know they are trash products and a trash company. It's beyond reason, I was pretty patient with them and they just try to burn me. I mean issues happen, but it's not clear how long ago that filterstudy thing was and they still haven't fixed things at all. Then they act dishonestly when someone does notice.

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.

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!

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?

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.

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.

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 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 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!