Texan_Reverend

Texan_Reverend , 2 days ago

@beej Nah. At first glance, that's where my head goes, too.

Texan_Reverend , 2 days ago

@Yuriel That is not even a little bit true about this instance.

Texan_Reverend , 2 days ago

@VeeRat Unfortunately, these types of in-nose filters perform worse than procedure/surgical masks, less than 30% filtration:
https://twitter.com/ghhughes/status/1719822719729160580?t=r_dwneIodGO_wPF9_mGb_Q&s=19

They just don't have enough surface area to use filter media that has a major impact. If they used filter media from something like a Dräger 1950 N95 or a 3M VFlex N95, you'd never be able to breathe through them.

Texan_Reverend , 2 days ago

@EricCarroll @VeeRat Those filtration claims are only 65% for 2.5 micron and 90% for 10 micron particle sizes. The most penetrating particle size for respirators, HVAC filters, HEPAs, etc. is 0.3 microns. That's the size that N95s still have to block 95% or more of.

With Gerard finding 29% filtration using a PortaCount fit tester which measures from 0.02 microns to 1 micron in size (covering that most penetrating 0.3 particle size), I figure that's at least close to what Protego's would score.

Texan_Reverend , 2 days ago

@EricCarroll @VeeRat While it's certainly not nothing, and anything's an improvement if your right to wear a proper respirator gets stripped away, I would only use these as a last resort and in conjuction with as many other mitigations as possible.

I hate that we're in a situation where anybody might have to do this sort of calculus.

PS: these might also be a reasonable combo with portable HEPAs for dentist visits and other medical procedures that require respirator removal.

Texan_Reverend , 2 days ago

@toba @EricCarroll @VeeRat I strongly agree. It's just the only case I could come up with (outside of being the only option left that isn't banned) where it might be worth anything. There might even be some medical procedures where the ReadiMask setup isn't viable, but most dentistry should still work fine with it.

Texan_Reverend , 3 days ago

@inelliotshead What can you say? They make good shit.
I got two for my house when we had to replace ours.

Texan_Reverend , 4 days ago

@amelie Some of my favorite comedy is that which plays it completely straight - totally earnest and invested in the world being presented. However, the absurdity or the references or the send up of another genre push it over into hilarious.

One of my favorite examples is True Lies. To all the world, just a Schwarzenegger blockbuster Summer action flick. However, it's an over-the-top Bond/spy movie riff with 90s James Cameron's excellent action mixed with almost Naked Gun levels of campiness.

Texan_Reverend , 3 days ago

@tty @yosh I'll jump in and share this study:
https://www.nature.com/articles/s41370-021-00337-1

It not only compares N95, KF94, KN95, cloth, and procedure/surgical masks; it does so on people at different stages of beard growth to show how that degrades respirator seal and function.
Also tested in this study was the ability of exercise bands/loops to contain facial hair and obtain proper respirator seal. (Spoiler: they work great!)

Hopefully, this helps you. There's even a nice clear graph for sharing.

Texan_Reverend , 3 days ago

@tty @yosh One of the things made clear by that study is that despite N95, KN95, and KF94 all using similar meltblown, electret filter material (which meets nearly identical filtration thresholds), the headbands required by the N95 spec make a huge difference in respirator seal effectiveness.

There are still both good and bad models of each of these respirator types, though, and specific model testing/recommendations are generally much more helpful when deciding what to protect yourself with.

Texan_Reverend , 5 days ago

@amelie They actually wear bifocals and keep the eye locked at a fixed focus. I love the idea of needing glasses for a mechanical/bionic eye.

Texan_Reverend , 5 days ago

@amelie Alternatively, the focusing could be fine, but the aperture blades grind. So, they either leave it at a wide-open fixed aperture and have to wear sunglasses indoors like folks with light sensitivity just to be able to see well at night, or they close down the aperture a bit for daylight and become one of those people who can't safely drive at night.

Added effect of wide-open aperture: everything is always really shallow depth of focus with strong bokeh blur on unfocused areas.

Texan_Reverend OP , 6 days ago (edited 4 days ago)

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.

2/3

Texan_Reverend OP , 6 days ago

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.

3/3

Texan_Reverend OP , 6 days ago

@mastobit @themaskerscomic There are other MERV-13 filters which work well. However, the Filtrete brand is thoroughly tested and has excellent quality control. It's easy to trust, and when purchased at Costco, rarely much more expensive than cheaper brands on Amazon. As a result, I prefer to make the specific recommendation of Filtrete for people who aren't as experienced with these devices and need a known-good option. That said, MERV-13 is the filtration level that needs to be met by these.

Texan_Reverend OP , 6 days ago

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.

Texan_Reverend OP , 6 days ago

@Njord Indeed! There are several variants, as different regions have different filters and fans available. There's a good UK version of this infographic using a common type of box fan there, and I've seen other designs that use IKEA filters like you mentioned.

Texan_Reverend OP , 6 days ago

@keithzg Bearing type, DC vs AC motor, blade shape, and all manner of other factors come into play. Plus, as you say, quietness is a major selling point in the PC fan market, so engineering work has been done on it.
However, box fans have remained largely unchanged for decades, with the exception of converting from mostly metal to mostly plastic.

Texan_Reverend OP , 6 days ago

@melanie Agreed. The basic 20"x20" box fans available from stores like Home Depot, WalMart, Canadian Tire, Target, etc. are mostly all reasonable.

However, when ordering from Amazon or similar, I'd stick to known brands like Lasko, Utilitech, Pelonis, Mainstays, etc. (Some of those are house brands for particular stores, but still good.)

All that said, with the way costs have risen on box fans in recent years, they're now the same price in the US as the 5-pack of quieter Arctic PC fans.
Wild.

Texan_Reverend OP , 6 days ago

@mavori Yes, there are a variety of regional variants on this core idea based around locally available filters and fans. I love seeing all the different ways people have been able to adapt the concept to fit their own situations. Yours is a particularly beautiful piece! I love this air filtering coffee table sort of look.

Texan_Reverend OP , 6 days ago

@energisch_ If the box fan isn't a good option in your area, you could try the PC fan version I mentioned in the second post of the thread:
https://kind.social/@Texan_Reverend/112432147641559401

Alternatively, you could try Google searching for: Corsi Rosenthal Box Germany.
That pulls up some options and ideas for how others have adapted the design with materials available in your area. I hope you figure out a solution that works well for you. Tschüs!

Texan_Reverend OP , 6 days ago

@viq I know I've seen several people in Europe using a IKEA HEPA filters and PC fans. Perhaps those materials might be more available in your area?

Texan_Reverend OP , 6 days ago

@MelodyWainscott Correct. This air cleaner design uses particulate filters and is only designed to handle airborne particles.

To deal with VOCs or other fumes usually requires activated charcoal or other specialized materials.

Texan_Reverend OP , 6 days ago

@suetanvil Yes, indeed!
Naomi Wu's design is great, and I really like some of these durable chassis models. However, they do add a considerable amount to the cost, so they aren't my starting point for a recommendation. If folks have the means to go this route, it's certainly a reasonable option!

Texan_Reverend OP , 5 days ago

@MelodyWainscott @trendless Because of the way activated carbon gets used up, thin prefilters and carbon-impregnated HVAC filters tend to have any benefits from the carbon used up quickly - long before the regular filter portion needs to be replaced. So, to have a really substantial impact which lasts a long time, it usually takes pounds/kilos worth of carbon in the unit. This model from Austin Air is a good example:
https://www.sylvane.com/austin-air-healthmate-air-purifier.html?utm_source=cj&utm_medium=affiliate&utm_campaign=cjaff&utm_term=%7B5513721%7D&utm_content=%7BWirecutter+Inc.%7D&cjevent=576f2b97116211ef80af33050a1cb828
It uses 15 pounds of activated carbon.

Texan_Reverend OP , 5 days ago

@MelodyWainscott @trendless I certainly won't dissuade you from experimentation, but there's pretty good evidence out there for needing rather significant quantities of activated carbon to achieve long-lasting, substantive results.

Texan_Reverend OP , 5 days ago

@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.

Texan_Reverend OP , 5 days ago

@suetanvil Personally, I still prefer the original DIY 4-filter design, as it shows better filtration performance when using the same number of fans:
https://www.texairfilters.com/comparing-the-performance-of-corsi-rosenthal-boxes-made-with-box-fans-and-pc-fans/
However, the Clean Air Kits tend to have more fans to offset this while maintaining a slimmer footprint. Both methods are solid performers, and it largely comes down to preference/priorities. Things like footprint, ease of filter replacement, aesthetics, etc.

Texan_Reverend OP , 5 days ago

@viq Of course, it always comes down to what's actually available in your own region. I can only confidently speak for what's available in the US and Canada where I shop and have done substantial research into availability. I know that it's not always the best option everywhere, and I wish more people had easy access to the materials needed to assemble devices like these at reasonable prices.

Texan_Reverend OP , 5 days ago

@xiroux Here's one that compares different CR Box designs to a commercial HEPA:
https://www.texairfilters.com/comparing-the-performance-of-corsi-rosenthal-boxes-made-with-box-fans-and-pc-fans/

This write-up points out some pros & cons while highlighting use-cases where HEPAs are still important, like hospitals:
https://blog.activepure.com/corsi-rosenthal-box-vs-air-purifiers/

Here, a CR Box is compared to a couple of commercial HEPA air cleaners with a focus on use in classrooms:
https://itsairborne.com/comparing-hepa-filters-and-the-corsi-rosenthal-box-a8b6d03af905

And to find even more, you could try web searching something like: Corsi Rosenthal Box compared to HEPA.

Texan_Reverend OP , 5 days ago

@solanum Yeah, the noise level is the biggest downside to the standard design. Fortunately, at least in the US, the cost of a 5-pack of Arctic fans plus the 12v power supply for them only comes out to a $10-20 premium over a typical box fan. So, it's not an exorbitant increase to go for a quieter model.

Plus, that's a one-time cost. It doesn't change anything about the replacement filter costs, and the PC fans even use less electricity.

Texan_Reverend OP , 5 days ago

@glasspusher Additional power controllers like that are great ways to extend the utility of existing box fan CR Boxes by letting you make them quieter.
However, if quieter is the goal for a new build, I would still recommend going with PC Fans. There's no sacrificing of performance to make them quieter, so you can easily leave it fully running all the time. Plus, the cost is a wash when compared to adding on a Variac to a box fan build.
I'm quite glad it's been so helpful in your implementation.

Texan_Reverend OP , 5 days ago

@VE2UWY Yeah, individual pricing on the filters is always rough, but even moreso in Canada. That's why Costco is my go-to, as a 4-pack of Filtrete 2200 filters is $75 CAD regardless of which size you pick:
https://www.costco.ca/3m-filtrete-mpr-2200-1%22-premium-furnace-filters%2c-4-pack.product.4000178960.html

For the same price, that's why I always pick the 20"x25" or 20"x30" to get the longest filter life and lowest restriction for the fans.

Texan_Reverend OP , 5 days ago

@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 OP , 5 days ago

@Simplicator @keithzg Yes! I would love to see a low-noise model with a DC motor and ultra-smooth bearings like a PC fan.
However, I suspect that the price of such things for that size of unit would make the resulting product cost-prohibitive. Likely much more expensive than a set of commodity, mass-produced PC fans.

Texan_Reverend OP , 5 days ago

@xiroux You're quite welcome, and I hope it's helpful.

Texan_Reverend OP , 5 days ago

@Hicsumus Here's a test of a couple PC fan variants compared to a traditional box fan model and a commercial HEPA purifier:
https://www.texairfilters.com/comparing-the-performance-of-corsi-rosenthal-boxes-made-with-box-fans-and-pc-fans/

Also, I'd have to find where I got the info again, but rough CADR for the P14 with Filtrete filters is 50 CFM per fan, and the P12 gets around 35 CFM. However, the two-filter models don't really increase in total output beyond 6 fans. The four-filter models do fine up to at least 9.

Six P14s will roughly equal a box fan on low in most testing.

Texan_Reverend OP , 5 days ago

@Stinkie Indeed. The four filter arrangement gets better airflow for the fan, and the filters will generally last around four times as long as a single one, if not longer. So, the cost over time is usually better with the full CR Box.

If you can afford the up-front cost, they're also cheaper per unit as a 4-pack than they are individually. A single filter is $17-30, depending on the store. The 4-pack is $60 from Costco, making them only $15 each.

But if all you can afford is 1, it still works.

Texan_Reverend OP , 5 days ago

@stargazersmith Yes, that's correct. The top center image in the graphic shows a completed unit with air arrows flowing in through the filters to blow up and out through the fan.

Texan_Reverend OP , 4 days ago

@chrisfromredfin As it says, the goal is to pull in air through the filters, and the top center image of a completed unit shows air passing in through the filters to blow out the top.

It would matter if this were reversed. The fan would then be catching and building up a great deal of dust. Plus, the filtration would be much less effective, especially if the filters were still arranged for inward airflow as directed. Distribution of clean air through the room also improves with upward airflow.

Texan_Reverend OP , 4 days ago

@WetFish Here's a reply I already made with some North American testing links:
https://kind.social/@Texan_Reverend/112435844042843600

In addition, variants on the design using locally available filter and fan models have been assembled and tested in the UK, Europe, China, India, and many more places.
I encourage you to dive as deep down this research rabbit hole as you like.

Texan_Reverend OP , 4 days ago

@voxofgod Less effective than what? I mentioned that the Corsi-Rosenthal Box generally performs better than common HEPA purifiers from Amazon, WalMart, etc.

For HVAC systems, it depends on the type.
Assuming a ducted, forced-air system, the best plan is to stick a Filtrete 1900, 2200, or 2500 filter on each return intake.
If you have a ductless, window, or portable AC unit, you're better off using a separate device - like this CR Box - as opposed to messing with the airflow of the AC.

Texan_Reverend OP , 4 days ago

@ideogram Unfortunately, that's the reality for many regions outside North America.

A pack of 4 Filtrete 1900 filters from Amazon plus a 5-pack of PC fans and the necessary accessories would run in the neighborhood of $265 AUD. It would match or exceed the output of most HEPA units while being much quieter, but you may be able to find complete HEPA units enough cheaper locally.

There are also units based on IKEA Starkvind filters you could look into for ideas. Those filters are $20 AUD each.

Texan_Reverend OP , 3 days ago

@starlily Yep, that's the simplest form of box fan air cleaner, and it's a totally functional option.

The CR Box just improves on those capabilities: lower motor stress, higher airflow of clean air, longer filter life, better room air mixing, lower noise, and so on.

If you prefer the single filter approach, great! The air cleaner that actually gets used is the best kind. Plus, the single filter + box fan is more affordable to start. However, it may need a new filter before smoke season ends.

Texan_Reverend OP , 3 days ago

@too_little_caffeine Oh, I'm quite familiar with Clean Air Kits, and I love them!
https://kind.social/@Texan_Reverend/112435598916372245

However, they're double the price of a CR Box and don't include filters. They're a great product, and they're not tremendously expensive for what they are and how they're made. I just can't make them my default recommendation due to that higher cost. That's where a DIY CR Box still solidly wins out.

Texan_Reverend OP , 3 days ago

@DavidM_yeg @suetanvil Yes, indeed! They're basically direct replacements for the box fan of a DIY CR Box - they just use different filter sizes from the box fan version.