Today, I was asked about effective air cleaners, because wildfires have already begun to flare in North America.
Extensive global testing has found that a DIY #CorsiRosenthalBox will outperform almost every commercial HEPA unit while costing less to run.
For the US & Canada, the best source of filters to build one is Costco: Filtrete 1900, 2200, or 2500 models with at least one 20-inch dimension.
These units also help mitigate allergens and infectious aerosols like #Covid and Influenza.
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A quieter alternative to the traditional box fan for a #CorsiRosenthalBox is to mount 5 or 6 Arctic P14 PST computer fans under a piece of cardboard/foam core/poster board instead. (They come in 5-packs.)
It can increase the initial cost a bit, but I feel the ability to comfortably run the unit 24/7 makes up for it.
To power the fans, you need a 12v fan power supply like this:
https://www.amazon.com/dp/B0BBSBV9CF
Mounting screws should be #6-32 x 1-3/4" with #6-32 hex nuts and optional #6 washers.
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If you want to cover the PC fans to keep little fingers or paws safe, you can use PC fan grills, baking tray grills/cooling racks, or gutter guard mesh.
Also, I recommend getting the tallest filters you can, 20"x25"x1" or 20"x30"x1", because the greater the filter area is, the longer they last and the less they restrict the fans' airflow. At Costco, they're even the same price as the smaller 20"x20"x1".
PS: painter's tape works as well as duct tape while being less sticky to work with.
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PPS: if you're in the US or Canada, the least expensive source for the Arctic P14 PST 5-pack is Amazon:
https://www.amazon.com/dp/B07HC782D5/
It's cheaper for Canadians to order from that link and pay the additional shipping fees than to order them anywhere I've found in Canada. Same is true of the 12v fan power supply linked upthread.
Costco.ca has the Filtrete 2200 in a 4-pack, Costco.com has the Filtrete 2500 4-pack, and neither site requires a membership to order them online.
With a box fan, the cardboard box it comes in is already a perfect size to use one face as the floor of a #CorsiRosenthalBox and the other face as the fan shroud.
For the PC fan version, you can use the manufacturer's cardboard box that the Costco 4-pack of Filtrete filters ships in the same way - one face gets cut to size for the floor, and the other face gets cut to the same size for the top but with holes added where you mount the PC fans. You could maybe double the top for more rigidity.
For a non-DIY, professional looking, and flat-packable air cleaner that's great for both travel and stationary usage, here's the $150 AirFanta 3Pro:
https://amazon.com/dp/B0CJTYWQBT
It's capable of box fan amounts of clean air delivery at much lower sound levels, and it takes up less space while being just as good against smoke and viruses.
Also, it's perfect for folks who don't want to deal with taping all the edges together or who want something that looks more like a product and less like a project.
@kumakaori74 In that case, there's always the CleanAirKits 6 fan plate:
https://www.cleanairkits.com/products/brisk-box?variant=47660329173292
You can pair it with a 4-pack of 16"x25" Filtrete 2500 filters to make a more traditional CR Box:
https://www.costco.com/3m-2500-series-filtrete-1-filter-4-pack.product.4000181409.html
It still requires taping the edges, but the fan plate makes an excellent replacement for a box fan, as it's much quieter. With white tape, the whole thing looks pretty nice and cohesive - still less experimental looking than with silver duct tape.
You can also get actual appliances now. We have one of these (haven't gotten around to assembling it yet, though):
https://cybernightmarket.com/products/the-nukit-tempest-air-purifier-kit
It's a metal PC-case-like box that holds filters and fans.
(I briefly pondered getting Gamer PC LEDs and RGB fans for it, but $SPOUSE nixed that. And also, I don't know enough about it to keep the cost/airflow ratio low enough.)
True. I have enough money that I didn't want to cheap out on this, and I'd planned on just getting a well-reviewed home air purifier but it turns out that the CR box is the best thing available.
@suetanvil If you're comfortable spending a bit more and you're looking for a complete solution with a frame, you could check out some of the offerings from https://www.cleanairkits.com/
They use quiet Arctic fans like I prefer, and they're designed to use standard 1" HVAC filters, preferably Filtrete, as they're the best performers in that form factor due to their micropleating. However, you're not locked into a particular brand or limited in store options for buying replacements.
Clean Air Kits are super efficient air purifiers built simply from banks of silent PC pressure fans and 3M Filtrete virus+allergen filters. Quiet enough to leave on always, powerful enough to protect from airborne pathogens like Flu, RSV, Strep, & Covid-19
I have several of these from clean air kits: as a musician / music teacher the ability to run something quietly is very important. I noticed last time I visited the site that they now have a 4 and 6 fan cubes as options.
@suetanvil @Texan_Reverend thanks for this!
If you have an airborne particulates sensor and a stick of incense, you can see that without the CR box particle counts go up rapidly and can stay in the air for like 18 hours after emission, but with the CR box running, levels are kept low and clear out to nothing within a few hours.
Tip #1: having 2" thick filters dramatically increases airflow.
Tip #2: if you have pets, simply wrap the CR box in a bug screen like you'd use for a window - cut to size and tape that in place over the filter, and they won't damage the it by scratching
@sleepfreeparent @suetanvil Yes, window/bug screen or some garden screens are all great ways to mitigate damage to the filter material from pets and kids.
As to filter thickness, that's true when comparing against almost all brands of 1" filter. However, Filtrete is the exception. Their micropleating allows them to match or exceed the airflow of most 2" filters, which is why they're often a bit more expensive than budget MERV-13 filters on Amazon. Usually better priced than 2" models, though.
@Texan_Reverend I've been enjoying @jcorbin's development of the PC HEPA, inspired by the exhalaron but looking like something you might want to see every day and portable to boot!
@Texan_Reverend I've been using the box fan with a variac I have. The variac is great at dialing the speed of the box fan down to very quiet levels. I also have particulate sensors, so I know when to dial things up.
The last few years with the wildfires in California have made me a smoke mitigation expert!
https://www.amazon.com/dp/B0CZ3NTMJQ/ref=sspa_dk_detail_2?pd_rd_i=B0CZ3NTMJQ
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