this post was submitted on 08 Jul 2025
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Mildly Interesting

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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

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[–] GlassHalfHopeful@lemmy.ca 116 points 1 day ago* (last edited 1 day ago) (2 children)
[–] Psythik@lemmy.world 44 points 1 day ago (1 children)
[–] baldingpudenda@lemmy.world 13 points 1 day ago (1 children)

I got MERV 13 filters to help with my kids allergies. Inside the house, perfectly fine, but once outside it's sneezing and runny noses. It's amazing.

[–] bear@lemmy.blahaj.zone 4 points 1 day ago (3 children)

Do you know how much power it uses?

[–] amino@lemmy.blahaj.zone 6 points 1 day ago (1 children)
[–] anomnom@sh.itjust.works 2 points 1 day ago

Techingredients just did a video on ceiling fan designs and realized that DC motors are vastly more efficient.

They also figured the cost savings to pay for the motor change, and it didn’t take long to pay off.

https://www.techingredients.com/videos

[–] baldingpudenda@lemmy.world 4 points 1 day ago (1 children)

I looked up a 20 inch box fan on Amazon and it was rated for 67 watts. I ran it almost 24 hrs a day(kids loved to mess with it) and didn't notice it on my bill.

[–] nulluser@lemmy.world 17 points 1 day ago* (last edited 1 day ago) (1 children)

67 watts is 1.608 kilowatt hours per day. In California (one of the more expensive states for electricity), electricity costs $0.31/kwh. That would come to just under $0.50/day or $15/month.

[–] Nollij@sopuli.xyz 8 points 1 day ago (1 children)

Watts per hour isn't a thing. Watts is already a measurement of rate. 67 watts, running for 24 hours, is 1.608 kilowatt-hours.

The rest of your math checks out, assuming no hidden "distribution" or "transmission" fees (like I have).

[–] nulluser@lemmy.world 7 points 1 day ago* (last edited 1 day ago)

Thanks for the clarification. Fixed.

[–] Smokeydope@lemmy.world 4 points 1 day ago* (last edited 1 day ago)

Hi, electrical systems engineer with an offgrid solar system powering fans I tested with meters signing in.

The typical fans you can buy in consumer stores are about 100W on average a little less on low aroubd 80w a little more on high like 110-120w.

They make more energy efficient fans, particularly brushless motor DC powered fans meant for marine boating power systems are incredibly energy efficient and quiet but they're also incredibly expensive.

Also keep in mind consumer fans kind of suck compared to a true industrial fan which can take a lot more power for serious wind speed output which the Wikipedia for this device says improves efficiency of purification. You can get power tool industrial fans that run off dewalt tool type batteries that are low DC voltage but high amperage, they'll be more powerful than typical consumer fans too but run out of juice battery wise within hours.

I personally like the 10-15watt DC fans with pass through USBC charging for personal cooling but thats not what were talking about.

[–] Korhaka@sopuli.xyz 16 points 1 day ago (1 children)

Been aware of the general idea for a long time, but had no idea that strapping HEPA filters to a fan has a fancy name.

[–] Diurnambule@jlai.lu 6 points 1 day ago* (last edited 1 day ago) (1 children)

You have to cut some cardboard and use tape too. After when your solution beat every commercial solution you are allowed to name it, just to be able to shame corpo easily.

[–] Korhaka@sopuli.xyz 2 points 1 day ago (1 children)

Could use those circular filters stacked on each other and a fan at the top. Name it my column.

Didgeridoo air filter is also tempting me now.

[–] Diurnambule@jlai.lu 1 points 1 day ago

Dongderidong air filter ?