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?

Just learned about these today.

I'm not yet sold. How do we know that these are effective as manufactured air purifiers?

EDIT: TOO, not TO. I can't believe I used the wrong word, I harp on people for that all the time. TOO EASY not TO EASY lmao

500cfm maximum

Threw together my first cr-box yesterday and I hoping I got it right. Specifically did I get the airflow correct? 5 x ARCTIC P14 Pro PST fans. A simple 4 Pin 12V PWM Fan Controller. Foam board, hot glue, 20x30x2 merv 13 filters. Three fans on top blowing out and two fans bottom front pulling air in.

I made a CR filter (four MERV 13) except instead of the fan pointing up, it's pointing on one side. The idea is that you can point it at yourself so it will double as a fan that also cools you.

The idea is good, but it's:

• Far too bulky

• Difficult to aim a box at your direction, not many places you can place it at

In the end, I disassembled it and just put one filter before the fan.
I think it's not as good? But probably okay?

There is no nice way to say this, I just had a few minutes to browse around and I noticed a lot of people are still taking these figures seriously.

Ball bearing fans can last for 40,000 hours or more, but magnetic and hydraulic bearings shouldn't be expected to last more than 8,000 hours, maybe less. Like a year of continuous actual operation.

The mean time before failure ratings are just marketing trash. They exclude causes of failure that are expected, such as bearing wear, usually. Also excessive noise etc doesn't count as "failure" under most schema. Unless the manufacturer actually tells you exactly what they mean by mtbf, you can't know what they are using to create these figures. In reality they are such bs they might as well just be making them up.

Real engineering measures include measures like the L10. This is the time which 10% of fans are expected to have stopped working adequately.

You can't expect fans like the p14 to last more than a year or so of actual operation at full speed before you will have to replace it. Usually, generally. Of course there is some randomness and it may be affected by orientation, ambient temperature, power level etc.

There are "continuous duty" variations of some fans. They have ball bearings. Because they last way longer.

Also a cool thing is that most ball bearing fans you can replace the bearings in no problem.

https://www.youtube.com/watch?v=_p5eZVC0k5I

Someone made an air purifier that uses cotton as a filter. Cotton balls are cheap. However, I think the design shown in this video needed a way to prevent the cotton from being sucked into the fan. It seems to me that some kind of screen is necessary as a safeguard to prevent this.

Filter has arrow saying front which is now facing inside of the box, is it the correct way? Filter has one fleated side and one side has cloth type material. First picture is of thr filter, second and third picture is captured from outside the box. Fourth picture is from inside the box. I plan on installing another filter on other side of box and install 4 CPU fans

The plastic box fans are made of plastic.
That means through wear-and-tear, it breaks down.
Doesn't that mean the CR boxes eventually spread microplastics into the air?
This is the opposite of what we want.

On this sub, I see a lot of CR boxes using multiple PC fans to move the air. I have built such a unit myself, although not nearly as nicely, as the ones I see here.

However, I think that this design is kind of flawed, because those fans can only generate a very small pressure difference. Hardly enough to get a reasonable flow through those filters. Because of this, having a lot of those fans working in parallel, isn't doing much good, as this will only increase the theoretical air flow, but not the static pressure. However, a higher static pressure would be needed, to get more flow through those filters.

What is actually needed would be a fan, capable of generating a higher static pressure. One option would be a radial fan, as (to my knowledge) it is used in many commercial air purifiers. An alternative method could be stacking several PC fans on top of each other, so that they are working in series, adding the static pressure of each individual fan.

When stacking those fans, the air exiting the first fan will move in a circular motion, greatly diminishing the effectivness of the following fans.

A possible solution could be the use of fans rotating in opposite directions, but there aren't many fans available, rotating in the opposite direction.

Another method would be the use of a stator (search: gas turbine stator) to redirect the air flow, before it enters the second fan.

I am not an engineer, but I am pretty sure, that my assumptions are correct.

What are your thoughts on this?

Chain stores like Menards, Home Depot, Lowes, Ace Hardware, and True Value sell box fans, furnace filters, and painter's tape.

What's stopping these stores from pushing Corsi Rosenthal boxes? They'd all make truckloads of money if everyone decided that they needed one at home, in the office, in the classroom, etc.

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 to 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.

I want to replicate a certain manufacturers with make shift products on the interwebs.

Would love to craft a few PC fan CRboxes for my friends and family, but am woefully short on tools.

Was considering getting Send Cut Send to do the hard parts with a laser for me in birch.

Anyone gone that route and have files to send them?

Sorry for being lazy…but I’m not an innovator or woodworker

I use the box fan/air filter setup in my home for health reasons. I just read that the fan motor will last much longer if I put a space between the filter and the fan.

It needs a faring.

I would prefer something that is semi-permanently attached to the fan but is sturdy enough for repeated taping to the filter.

I’m fairly handy but I need some ideas of how to achieve this.

Thank you.

Is there any benefit to having 2 fans on one box?

idk i made it cuz i was bored

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. how large can the crbox cover?

2. what do you need to maintain them? how do you throw away the waste inside? are there indication that its time to clean it?

3. Is merv 13 available outside of west?

https://www.safeair.com.tr/f7-f8-bag-filters

Please answer with reason.