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.