A CR box, or a Corsi-Rosenthal box, is a very efficient, low-cost, make-it-yourself air filter that was developed by two environmental engineers, Richard Corsi and Jim Rosenthal.

The standard is a box fan taped to four MERV-13 furnace filters (like this: https://youtu.be/aw7fUMhNov8 ), but people have adapted them to use computer fans and one or two filters to fit in their space (examples here: https://mobile.twitter.com/hashtag/corsirosenthalbox?src=hashtag_click&f=image and specifically here: https://mobile.twitter.com/robwiss/status/1596940686049554434 ).

Because of the high volume of air a box fan is able to pull through the large surface area of filters, it ends up being pretty similar to or better than a hepa filter in terms of particles filtered, and they’re cheaper and have less plastic and electronics waste. Testing shows that they’re also quieter than many standard air filters: https://mobile.twitter.com/marwa_zaatari/status/1499072595404206090.

I recommend building a CR box. They're cheaper to build than air purifiers are to buy (even more so if you're comparing them based on how much air they filter). While the standard one--a cube of 4 MERV 13 filters with a box fan--is quite large, people have made smaller ones with computer fans or CR boxes with one filter set as a floating shelf. The BIFL aspect is that it's just a fan (which is always useful) and filters (which you'd need to replace on any air purifier). The filters aren't proprietary, too, so you can search for sales and you're not locked into one company or one size.

I have a horsehair broom and a corn broom from redecker. Both are amazing. I’ve had the horsehair broom for about 10 years and it still looks like new. I also love that it’s plastic free! I am really careful, though, to store it with its bristles up, which makes a huge difference.

That's awesome! I had heard of Fairphones before (and will get one if/when my phone dies), but I had no idea that there was a laptop equivalent. Thanks!

If you think it might be partly lime scale, then some citric acid (or lemon juice) with some boiling water would help. For stains, washing soda and hot water helps. If you just bleach it, then you'll remove the colour without affecting whatever's holding onto the colour.