Measuring My DIY Air Purifier | Hacker News Reader

Measuring My DIY Air Purifier

chillphysicsenjoyer.substack.com

75 pointscrescit_eundo11 comments

I'd be interested to know the decay rate when neither the window is opened or the air purifier is on.

Not the Op but I have PM 2.5 sensors in my house. There is one next to the stove, another in the main bedroom above the kitchen, another in the office above the main bedroom, and another in the garage.

Here's two samples. One was last night when I cooked pancakes, grits, sausages, and hash browns on a gas stove. The fan came on at 6:35:37.

The other is cooking one fried egg in the morning for breakfast.

https://imgur.com/a/zwBU6wA

Power consumption (maybe CADR per watt?) is also interesting to measure. From what I've seen, that is the main dimension where homemade purifiers can lag behind dedicated ones. Well, that and aesthetics which is more subjective :)

The CR-boxes are rather bad in that regard, but the newer generation of PC-fan builds are significantly better than mainstream HEPA purifiers:

https://housefresh.com/cleanairkits-luggable-xl-review/#the-...

For comparison sake, a 20 inch box fan, which many CR filters are made from, consume 60-85 watts depending on their speed, which is 50-100% more electricity.

This could be improved by finding more efficient fans, but if you're going for the cheap $25 fans at your local big-box store, you'll pay more for it over time in electricity costs.

I have one as well, but I live in a geodesic dome home and use it in the largest open portion of my house.

The ceiling at its highest point from the lowest point is 18 feet up, and the open section is about 1/2 of my entire home, so the one 20" fan keeps air circulating and being filtered for an enormous portion of my home.

If you live in a more typical home, the 20 inch box fan CR filter might be overkill.

The $2 PC case fan wins on both price, power consumption and quietness, and seems able to filter a roomful of air in an hour or so.

You will spend a bit more buying a few of them, a 12v power adapter, and the shell to tie everything together, but you are correct.

If you buy the cylindrical air filters, you can pop one on a table, pop a case fan on top, and hook it up to a phone charger via a 20 cent Usbc adaptor.

As a bonus, the USB-C PD adaptor has selectable voltage (5, 9, 12v) on little dip switches, and that can be used as a speed control for a 12v fan.

Turn it up to max when cooking, and down to silent again when sleeping.

No need for any fixings or case or anything.

You must have very clean air already if such a puny fan would be able to keep particulate levels within acceptable limits. In winter, my Xiaomi purifier with a quite powerful turbine fan (or whatever those things are called — they're optimized for pushing air through dense filters) is barely able to keep PM2.5 within 5-10 micrograms on max speed (with doors and windows closed). A PC fan would make approximately zero difference, on or off.

I have a Luggable and love it! So quiet and yet loads of airflow!

I built around this thing, which I run at 10% throttle and which consumes 6 watts at that level:

https://terra-bloom.com/products/terrabloom-10-inline-duct-f...

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