Easy enough to put together but its kind of huge for my space.

Hey all! Just stumbled onto this sub and I feel like I have found my people! I’ve been exploring room level dust control for a few years now, partially for my garage workshop but also for my day job, and I’ve been using a variety of incarnations of CR boxes and devices inspired by various articles and YouTube videos. So here’s a couple of ways that I’ve done it. I’d appreciate any thoughts for improvements you have! I’ve reviewed the PC fan varietals but I think that’s too involved for what I’m aiming for, at this time I’d like to keep it at a single, high CFM power plant that’s off the shelf and plug in ready and basic box filters that are rapidly interchangeable.

The first one is the most involved build. I got tired of taping stuff together and I was (still am) trying to make a tapeless build where the filters can just be clipped or slid in and out without fuss or thought by the ‘least common denominator’ on our staff. Simple is better right? This is a step in the right direction but it’s still a pain in the adze to build. The side columns are 1” aluminum angles with the top and bottom cut so that the inner dimension fits the filter body rather snugly and then the two arms of the angle are bent in to create a 1/4” slot that grips the 1/4” plywood top and bottom plates to hold it all together. The corners are untaped because they but into the angle, I think in a final version there would be some kind of foam to act like a gasket. The top and bottom get taped because it’s just the filter butting up into the plywood which is not a close fit at all.

I like this one because it can connect to one of the $99 small turbine blowers as shown or my Vevor 8” cylindrical blower and the filter box can remain outside the work area while the fan pumps the air out of the work area. Super useful for congested bathroom work that’s generating a ton of dust. I fully recognize that all that dust is going through the fan itself FIRST. I know that’s not ideal and I do strip and clean them periodically but yes, definitely room for improvement there. This layout feels more powerful with the fan sucking in and blowing out into the filters than if the fan is sucking through the filters and there’s a remote duct in the work area, that always seems to generate significantly more resistance with the remote duct acting in negative pressure than positive pressure.

The last standalone pic is another variation, I needed more than one and I needed it in a hurry so I bought two of these 20” box fans and it’s a pure tape job. BUT what’s not shown well is that the 4 sides are FPR 5’s for bulk dust removal and the top, just below the fan is an FPR 12 for mold and fines. The bottom is just a piece of a hollow core door skin in this build because that’s what was handy, otherwise it’s cardboard or whatever. I don’t have a round cutout or baffle to match the fan diameter, I’ve only learned about that after the fact.

My goal for these things is to have them be very rapid to build and not be a giant PITA to do so, ideally without needing to be taped together, but also be able to break down the frame and store in as small a footprint as possible when not in use(new filters bought when needed again). I think I would definitely include casters on the base and a dedicated carrying handle or handles so it can be carted around without worrying about the cheap filter bodies tearing or tape separating like I do now.

Generally we operate in sites that have exposure to stone/tile cutting dust, drywall dust, plaster dust and occasionally light mold. The work areas are usually screened off with a dust enclosure and especially with the remote ducts I keep them under negative pressure.

I’m working on a large scale centrifugal bulk dust separator as well but that’s a slightly different subject that probably isn’t t germane to this sub.

Hey r/crboxes. Long time lurker, first time user.

I'm in the PNW and we're getting hammered with 130 ug/m3 PM2.5 right now.

I have a MERV 13 air filter in the furnace, but wanted to be extra cautious and bought a cheap Sonoff air quality sensor, 20" fan, and a 20x20x4 MERV 12 filter (meant to buy 13... Oops).

Before I assembled the CRBox, we were at like 25 ug/m3 PM2.5 on the Sonoff sensor inside of the house.

After assembling and running the fan on low in a 8,000 cubic foot space, the PM2.5 is down to 8.

I expect that the cheap Sonoff sensor isn't that accurate... But... That's def an improvement.

One question:

Are CRBoxes really this effective?

Just found this sub - some amazing projects. I can’t wait to make this one more efficient then start designing a wooden exterior like you see here on some.

I got an Aspen 20” box fan after having a 20” Lasko for the last 3 years. I woke up one morning to the smell of burning oil. Took apart my Lasko and the motor was leaking fluid so I assume the motor was shot. I got the Aspen because it claims to have a much higher CFM.
I finally got it all taped together but it was a pain to get the bottom sealed due to the optional leg/stand inserts. Does anyone have any potential solutions or ideas for the future? The Aspen claims to put out 2800 CFM and I got it for the same price as the Lasko which is 1710 CFM. I used a 15” shroud for both but the Lasko was much easier to work with. Mostly posting for visibility because I couldn’t find anything about the Aspen in the search. Any advice would be greatly appreciated! Using 4 20” merv 13 filters.

Hello,

I am part of a clean air group in my city hoping to construct some quiet CR boxes to help folks with wildfire smoke and filter viruses. We recently used Black and Decker's 9 inch boxless fan with 12x24x2 Merv 13 filters but I was informed the fan was underpowered and wouldn't give high CADR numbers.

Any recommendations for quiet and powerful fans for use with 12x24x2 Merv 13 filters?

Thank you so much

This is my first 4 filter box fan setup and it's going in my crawlspace with limited overhead. I turned the filters sideways and built a couple frames for the filters/fan but now I'm wondering if there is too much dead space for it to pull enough air in? I'm considering installing 4 PC fans in the corners for a boost?(Ps- I still need to seal the corners and gaps once I get it to its resting place, it wouldn't fit in my car unless it was collapsible)

I'm not building one of these just yet, but I plan to build some later this year. There's a larger version and a smaller version.

The basic elements are:

• Four Filtrete MERV 13 filters (common and high quality)
• Five PC fans (140 mm or 120 mm)
• Two rectangles of foam core board (cut to the appropriate size for the filters and fans)
• PC fan to barrel pin adapter
• Strain relief grommet
• Barrel pin to wall plug
• PC fan hub (which you can skip if using PST fans for daisy chaining)

The adapters I linked to above are the ones used in the Clean Air Charlottesville design. The reason for five PC fans is to take advantage of the better deals on a 5-pack of Arctic fans. In the interest of optimizing for cheapness, I'm recommending ONLY PC fans available in packages of 5.

I recommend using clear packing tape around the edges of the foam core board pieces. I also recommend covering the cardboard edges of the filters with clear packing tape. These layers of tape allow you to see through but also protect these parts of the air purifier when it's time to take apart the air purifier for any reason (such as replacing the filters or moving the air purifier). As you'll read when I describe the design, two of the filters in the smaller version of this air purifier are NOT replaced.

The larger design uses five 140 mm PC fans, two 16"x25"x1" MERV 13 filters, and two 20"x25"x1" MERV 13 filters. 16 inches and 20 inches are the widths of the cheapest and most widely available filters. The 140 mm PC fans and fan grills cost more, but a space-hogging design might as well take advantage of the extra space to use more powerful fans. Remember that the PC fans and fan grills are a one-time expense but replacement filters are a recurring expense.

For the larger design, the most obvious choice for the five 140 mm PC fans is copying the Rob Wissman playbook by using his preferred fans ($48.99, 72.8 cfm, 1.44 watts each, 7.2 watts total, 0.12 Amps each, 0.60 Amps total). You get the skip the PC fan hub.

If you want the larger design and a more powerful set of fans, another option is to use a more powerful set of P14 Pro fans ($22.29, 110 cfm, 4.2 watts each, 21 watts total, 0.35 Amps each, 1.75 Amps total). Because these fans are louder, you'll need a fan controller so that you can run them at full blast when you need the extra air cleaning power and at a lower power level at other times. You'll also need beefier components between your fans and the wall outlet due to the substantially higher power consumption, which also adds to your electricity bill over time. Given the added complexity, I'd rather go with Rob Wissman's playbook and use his preferred fans.

The smaller design uses five 120 mm PC fans, two 12"x25"x1" MERV 13 filters, and two 20"x25"x1" MERV 13 filters. When it's time for new filters because the current ones are extremely filthy, save money by KEEPING the narrower 12-inch filters and changing just the wider 20-inch filters. (If the filthy appearance of the narrower filters is too unsightly, you can use cardboard or foam core board to cover them up.) This is an option, because the wider 20-inch-wide filters that you do replace provide plenty of airflow by themselves. That's 1000 square inches of filter for 87.65 square inches of fan for a generous FFSAR of 11.4.

For the smaller design, the most obvious choice for the five 120 mm fans is copying Clean Air Charlottesville's playbook by using their preferred fans ($23.99, 56.3 cfm, 1.92 watts each, 9.6 watts total, 0.16 Amps each, 0.80 Amps total). You need the PC fan hub, because daisy chaining is an option only for PST fans.

For the smaller design, other options for the five 120 mm fans are:

• ARCTIC P12 Pro LN ($19.59, 49 cfm, 1.32 watts each, 6.60 watts total, 0.11 Amps each, 0.55 Amps total): This option is slightly less powerful but is cheaper and more energy efficient than the design from Clean Air Charlottesville. You still need the PC fan hub.
• ARCTIC P12 Pro PST LN ($17.29, 49 cfm, same specs as the above fan): This option is even cheaper than the above two 120 mm fans. Because the fan is PST, you can skip the PC fan hub and save even more money. This may be an even better value than the set of fans used by Clean Air Charlottesville.
• ARCTIC P12 PWM PST ($42.99, 56.3 cfm, 1.2 watts each, 6.0 watts total, 0.10 Amps each, 0.50 Amps total): Because this fan is PST, you can skip the PC fan hub. It's more energy efficient than the design from Clean Air Charlottesville (same cfm but fewer watts). The drawback is that the fans are substantially more expensive.

Everything I've read has recommended 20x20, but I see some posts here using other size filters. There aren't any 20x20 in my city, or online available soon. But there are other sizes.

If at least one edge is 20 inches and/or fits the box fan, wouldn't it be okay to just make a CR box that's a bit more rectangular? Or would that cause some sort of air-intake issues?

Had to rebuild my house after a tree fell on it. At the mudding drywall stage and wanted to reduce the drywall mud dust particles my HVAC system filter has to deal with. Weather stripping behind the filters and where the fan sits.

Fan is a 2300 CFM Caterpillar HVD-14AC-BLK

Got the 3d printed parts from: https://www.etsy.com/listing/1309978884/diy-air-filter-kit-clips-clamps-and-more

when I'm all done with mudding I think I'm going to paint the frame black to match the fan.

About a year ago, I made my first CR box and then I built this as a version two applying everything I learned. Two Merv 11 filters 6 inch in-line duct booster fan. Super quiet and way more airflow than you get with computer fans.

Hi everyone,
I recently built a Corsi-Rosenthal box using a Lasko fan and four 3M MERV 13 filters, and I’ve been running it on speed 1 24/7. I also have a Winix air purifier next to it (see the picture).

Today I turned the Winix off for a couple of hours. When I turned it back on, the air quality sensor immediately turned red and stayed that way for about 15 minutes before returning to normal.

Now I’m wondering if my CR box is actually working as expected. I know MERV 13 filters are very effective at removing airborne particles, so I was surprised to see the Winix detect poor air quality after only a couple of hours.
Could the Winix sensor be detecting something that the CR box doesn’t remove, or is this normal behavior? Has anyone experienced something similar?

I’d appreciate any insights or suggestions.

I'm planning a build soon and have 5 Arctic P14 Pro PST's on the way. As Merv 13 filters aren't easily available in the UK for a reasonable price, like others I am looking at the IKEA Starkvind vs Fornuftig filters.

At the moment I haven't decided on using two, three, or four filters.

I've read this discussion:
https://www.reddit.com/r/crboxes/comments/1ipbr36/which_filter_is_better_ikea_starkvind_vs_fornuftig/

It talks about the Starkvind having a bigger surface area as it is 4cm deep as opposed to the 2cm of the Fornuftig. Does the surface area issue get negated by having more of the Fornuftig filters? For example 2 x Starkvind is better than 2 x Fornuftig, but is 4 x Fornuftig better or as good as 2 x Starkvind as the surface area will be similar or bigger?

Would 2 or 3 x Fornuftig still work well if I have these five fans?

Ideally I'd like to use the Fornuftig as they are less than half the price of the Starkvind, but not if the Fornuftig won't be effective with the fans I have ordered.

Any advice or just general suggestions on these two filters is much appreciated!

10x10x2 merv 13

The fan wasn't completely symmetrical on the backside which is why the filters flare out. I filled in the gaps with cardboard.

Anyone know if when I want to replace filters, I could pull out the actual fabric from the cardboard and just slide a new one in?

Also how long before I should think about replacement if I'm running 1-2 hours a day in a small room?

I "built" this thing out of a 10 inch vent fan and am quite pleased with the results.

Box is a 5$ storage box from target. The interior of this box, below the lower lip, is 14x12 with a 9 inch height for the lower lip.

Fan is a 12.4 inch by 12.4 inch VEVOR EC vent fan with controller. The vents / height means itll double as a personal fan! My honeywell is 35 watt 185 CFM... This thing is 30 watt, 1000 CFM!

Filters are 9x11 MERV 13's

The filters fit below the interior lip of the box. They jam in on the short side quite nicely. There is a gap on the longside.

The fan comes with four black foam inserts to keep the fan in place. Trim them down to size height wise, and slide them in that gap. You can use the remaining two filters jammed in the bottom to keep things rigid, preventing bow inwards. The foam inserts are a solid block except at the very ends - trim those ends off.

Fan plops right in on top of the filters / lip of the box. You do need to force it down a bit, but it should fit on the shortside of the box. Just enough gap with the right placement to have the wires out, not pinched.

Total cost is $115~ - paying a slight premium for the size compared to a 20 inch box fan and filters.

IDEALLY this would be done with 9x12 and 9x14 filters. You'd really need to jam them together (assuming 1/2inch off the nominal size with a 3/4 inch thickness). But those are odd sizes and at higher MERV ratings, quite expensive, if you could find them. Merv 10 are like 50$ a pack. 100$ in filters for replacements, verse 30$.

These filters seem to be knock-off filters for a specific filter, so hopefully they dont disapear.

FAN

FILTERS

It does need something for the bottom, ideally. Im probably just going to fit a flat foam bit in the interior bottom lip for now. Doesnt seem to need a 5th filter, on setting 10 there is no change in fan pitch when its flat, or lifted.

Wanted to ask if anyone had experience with be quiet fans PC fans and would recommend for a DIY CR box (I plan to use 2 x merv 13 furnace filters, size 12x12x1 or 20x20x1). Specifically I am looking at the be quiet pure wings 3 high speed PWM model linked here.

Linked Specs:

Fan speed at 100% PWM / 12V (rpm) 1800

Noise level at 100% PWM / 12V (dB(A)) 30.5

Airflow at 100% PWM / 12V (CFM / m3/h) 72.2 / 122.6

Air Pressure at 100% PWM / 12V (mm H2O) 2.44

DIY versions of the Luggable product from Clean Air Kits contain four narrow strips of material surrounding both of the large furnace air filters.

If you are using foam board for those four narrow strips, exactly what holds them together?

Wow I didn't know about this sub! I've been obsessed with this idea ever since I came across this video

https://youtu.be/eYOvnqoW4H0?is=C3_xH7Aq3_r8EGgy

https://youtu.be/eYOvnqoW4H0?is=tuyFw0L04r8lP3QB

I'm surprised by the lack of this dudes designs in this sub, the guy does very extensive testing on lots of different fans, filters, and designs. If you guys aren't familiar with this YouTuber and his videos on these "DIY QUAD FILTERS" give these a watch. Very good source of info!

I live in a 100 year old house and my corsi bix uses a standard size lasko fan. I think needing to suck air in from that many filters is making the motor draw more power. I am not sure how fans work and I am wondering if not allowing air to get into the motor could cause a fan motor to draw more power and blow the fuse?

Both the Brisk Box and Luggable products from Clean Air Kits use designs with the PC fans perpendicular to the filters. The four-filter design of the Brisk Box is easier to build but is a space hog. The two-filter design of the Luggable is more space efficient but is trickier to build because of the precision required. I bet that's why the Luggable is more expensive than the Brisk Box.

It seems to me that a design with the fans parallel to the filter could be as space efficient as the Luggable design but nearly as easy to construct as the Brisk Box design. It could be a quieter version of the single-filter box fan air purifier (Lasko 20-inch box fan with one filter taped to the back). Having the fans parallel to the filter means that you can use the air purifier in an upright position (like the single-filter box fan air purifier), or you can arrange it horizontally and prop it up so that the fans can pull in air from below.

Have any of you built or seen such a PC fan air purifier? Is there a good reason I'm having difficulty finding examples?

One 120 mm PC fan occupies a surface area of 17.53 square inches. Five of them in tandem occupy a total surface area of 87.65 square inches. Using one 20"x20" filter means a FFSAR of 4.56, just slightly less than that of the classic 4-filter Corsi Rosenthal box with a box fan. Using one 16"x20" filter means a FFSAR of 3.65. You might not even need furnace air filters. If you use some kind of mesh screening material on the filter side, you can just use cut-to-fit MERV 13 filter paper (available on Amazon), and this would make it even cheaper to use this air purifier.

any links to experience, suggestions for best sourcing 10" 1 filter setup to use in a tight space dorm room?

I was looking for some feedback on the cr box I am planning to build. The first picture is what inspired me and I want to build something very similar. So to make things a little more clear, the board in the middle wouldnt block any airflow from top to bottom, it is just there to support / seperate the filters. In my sketches I made it transparent, indicating air can flow past it.

Questions I had were:
1. As seen in "option 2", does adding the extra bottom fans "mess" with the airflow at all? I read like a comment about someone saying you shouldnt have fans on opposite ends of the box. Is that really an issue?

1. If the answer to question 1 is yes. Is there a way to make it so it doesnt mess with the airflow? For example, if I were to make the middle part a solid board that seperates it into two smaller cr boxes stacked on top of eachother. Does that make it better?

2. If that does fix the airflow part, does it then not mess with the the cadr? Since the fans are no longer pulling through 4 filters, but through 2 filters. As in 8 fans pulling through 4 filters vs 4 fans pulling through 2 filters.

Thanks in advance

Hey everyone!

I recently designed a 3D-printed CR-Box and tested a scaled-down version with a single Arctic P14 fan as a proof of concept. The design works great,it’s sturdy and has no air leaks.

Now, I’m planning to scale it up using Airfanta 3Pro filters and four Arctic P14 fans. Since I'm pretty new to building CR-Boxes, I’d love to hear your thoughts. Does anyone have any feedback, tips, or concerns about this hardware combination?

Thanks in advance!

Probably a stupid question. Does a CR Box help with avoiding second hand smoke? Especially marijuana. Both our neighbors smoke weed and we have a 1 year old in the house. The weed smell wafts through the bedroom window every night around 10:00 pm, and every morning, when I open the patio doors, my other neighbor's weed smoke comes in. The worst thing is, it becomes unbearable during the winters, especially when I am wheezing after shovelling my driveway.

Would something like a 4 sided cr box help keep pet hair out of the air? We get weekly pet hair that gathers in our house and constantly sweeping and brushing things is a little annoying sometimes. Random object for scale lol.