this post was submitted on 08 Jul 2025
545 points (98.7% liked)

Mildly Interesting

21651 readers
562 users here now

This is for strictly mildly interesting material. If it's too interesting, it doesn't belong. If it's not interesting, it doesn't belong.

This is obviously an objective criteria, so the mods are always right. Or maybe mildly right? Ahh.. what do we know?

Just post some stuff and don't spam.

founded 2 years ago
MODERATORS
 

I recently stayed in an apartment that didnt have central air so I created a corsi-rosenthal box since the smoke from the Canadian wildfires were so bad.

After 30 days of continuous use, with very minimal periods of it being turned off, this is what the filters look like!

It's disgusting yet also so satisfying to see the filters get darker from debris, dust, and dirt.

Edit: typos

top 50 comments
sorted by: hot top controversial new old
[–] [email protected] 3 points 20 hours ago (1 children)

These are great, but if you’re looking for something slightly less bulky, there’s a dude selling kits online using pc fans. I’ve got two and they’re pretty much a CR box in its final form. Kits come with laser cut panels, fans, grates, etc. only need to supply two filters. Way quieter than a box fan. They’re a bit pricey but worth since they can pretty much be placed anywhere.

google clean air kits.

[–] [email protected] 2 points 17 hours ago

For that money, you can buy actual air filtration units. The box fan may be noisy, but something that big is going to have massive surface area and provide a lot of filtration.

[–] [email protected] 1 points 20 hours ago

I dont mean airflow as in rate of air moving through the fan, i mean it as in volume of air being filtered.

[–] [email protected] 25 points 2 days ago (2 children)

I'm just amazed it apparently took two people to think of taping 4 air filters together with a fan on top.

[–] [email protected] 2 points 22 hours ago (1 children)

Curious why it's not 5 filters with some little toilet paper tubes or something for legs. Was it found that the fifth filter is diminishing returns?

[–] [email protected] 3 points 21 hours ago

Sounds like an argument that would take at least two meetings and a dozen emails if this were done by a company lol.

[–] [email protected] 10 points 1 day ago

They may not have been the ones who first thought of it, but the first people to publish research that shows that taping 4 air filters together with a fan works decently compared to other, non-DIY filters (where "worked decently" means does a good enough job that it's worth doing if you want a filter but can't/won't buy or build a more complex filtering system, even if it isn't as good as "proper" filtering systems)

(Tangent: I'm reminded of the "Cox-Zucker machine", a random maths thing that Cox and Zucker made together because when Cox and Zucker met at university, they realised that their names, when combined in the traditional, alphabetical order, sounded "delightfully obscene". )

[–] [email protected] 3 points 2 days ago

I've put an air filter in the bedroom next to the bed. Makes nice white noise too. I also have one next to the cat's litter box. I'm thinking of putting one in the bathroom because the toilet paper makes an insane amount of lint that builds up everywhere.

[–] [email protected] 3 points 2 days ago

I built one back when I lived in California during fire season, and then again during the pandemic. They do such a nice job making the air less gross.

I think that's about what mine looked like after 3 or 4 weeks too...

[–] [email protected] 2 points 2 days ago (1 children)

My loft is so freaking hot I’m sweltering. Could something like this keep my loft cooler, the window unit is struggling to cool it off until late at night

[–] [email protected] 7 points 2 days ago (1 children)

No. This actually will heat up your apartment by a measurable amount. This is purely an air quality type thing.

[–] [email protected] 3 points 2 days ago (1 children)

*measurable if you have some damn good instruments.

It will put off about as much heat as a single incandescent light bulb

[–] [email protected] 1 points 1 day ago

Fair, and I would say < an incandescent bulb. Cause I'm damn near 40 and remember getting a good MiB experience touching one.

[–] [email protected] 2 points 2 days ago

OP likes it dirty!

[–] [email protected] 3 points 2 days ago (1 children)

We did one with just one filter on the intake side. Kinda like this one better. But it takes up more room than mine. I'll have to do some experimenting.

[–] [email protected] 5 points 2 days ago

Corsi-rosenthal box is stupid efficient.

[–] [email protected] 3 points 2 days ago

Wow that’s really quick for saturating those filters! Wildfire season is the worst.

[–] [email protected] 4 points 2 days ago (2 children)

Can you talk about how you made this

[–] [email protected] 4 points 2 days ago
[–] [email protected] 9 points 2 days ago (1 children)

It’s literally what you see in the picture. Just household furnace filters taped into a box with a fan. You can pick your level of filtration with the type of filters you buy.

[–] [email protected] 4 points 2 days ago (4 children)

Does the fan suck or blow, and why? I seem to recall that the motor will burn out if you face it the wrong way.

[–] [email protected] 2 points 1 day ago

It is setup to pull in air through the filters into the box and push it up through the top.

[–] [email protected] 7 points 2 days ago

Looks like it's sucking air through the filters.

[–] [email protected] 6 points 2 days ago

I would imagine it blows upwards, so it sucks in air through the filters and blows clean air up.

[–] [email protected] 6 points 2 days ago

In that pic it's blowing up, sucking intake through the filters and blowing filtered air into the room.

[–] [email protected] 3 points 2 days ago (2 children)

I'm viewing this post with the Thunder app and I only see one photo: a box with a fan on top. I see no filter. Is there supposed to be a second photo?

[–] [email protected] 11 points 2 days ago (1 children)

What you see are 4 hepa filter plates taped together into a box, with a fan on top. The fan blows air upwards, thus creating a low pressure environment inside the box, which sucks the air through the filters - which are originally starch white.

[–] [email protected] 3 points 1 day ago

Yep and if you want to get really fancy, ya can put the box on stilts and put a 5th filter on the bottom!

[–] [email protected] 16 points 2 days ago

The box is the filter

load more comments
view more: next ›