4 ms·

There’s always a <strike>bigger</strike> smaller <strike>fish</strike> particle.

by fooker 4y ago

bawolff 4y ago
From my understanding, medium sized particles are actually the most expensive to filter
- fooker 4y ago
  What's the intuition behind this?
  - LaputanMachine 4y ago
    Multiple physical effects are responsible for filtering. Each of them works best at certain particle diameters. The combined efficiency of all effects happens to have a minimum at 0.3 microns. [1] This is called the "Most Penetrating Particle Size" (MPPS). For very small particle sizes, filtering mostly works by diffusion (quoting from [2]): >[Diffusion] is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 μm in diameter. The small particles are effectively blown or bounced around and collide with the filter media fibers. This behavior is similar to Brownian motion and raises the probability that a particle will be stopped [...] [1]: https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_Collection_Mechanisms-en.svg https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_C... [2]: https://en.wikipedia.org/wiki/HEPA#Mechanism https://en.wikipedia.org/wiki/HEPA#Mechanism
    - schiffern 4y ago
      In the paper[0] they define "ultrafine emissions" as <0.1 microns. "Diesel Oxidation Catalyst (DOC) and Diesel Particle Filter (DPF) has been very effective in controlling the emissions of solid particles and hence BC, but that there has been little change in the liquid mode (<30 nm) particles, and that concentrations of ultrafine particles (<100 nm) still well exceed the threshold for “high” concentrations (>10e4 cm^−3 /24-hour mean) defined by WHO. BC declined by 81% between 2014 and 2021, but the ultrafine particle (<100 nm) count declined by only 26%. Looks like DPF/DOC filters use mainly interception, but they're not terribly effective at filtering via the diffusion mechanism. [0] https://www.sciencedirect.com/science/article/pii/S0160412023001617 https://www.sciencedirect.com/science/article/pii/S016041202...
  - jodrellblank 4y ago
    See: https://dynomight.net/ikea-purifier/ https://dynomight.net/ikea-purifier/ Scroll down to “The physics of air purifiers seem simple.” for the relevant bit.
maxbond 4y ago
Y̵o̵u̵ ̵c̵a̵n̵ ̵a̵l̵s̵o̵ ̵u̵s̵e̵ ̵U̵n̵i̵c̵o̵d̵e̵ ̵s̵t̵r̵i̵k̵e̵t̵h̵r̵o̵u̵g̵h̵ ̵c̵h̵a̵r̵a̵c̵t̵e̵r̵s̵
- fooker 4y ago
  It's discouraged here for the sake of accessibility. Screen readers and translators don't do well with these characters.
  - maxbond 4y ago
    Interesting. Thanks.
  - moffkalast 4y ago
    As a test I've pasted that into ChatGPT asking it to edit it so it uses corresponding letters from the ASCII table and it removed the strikethrough flawlessly. Probably won't be an issue for those screen readers for much longer.
    - fooker 4y ago
      Wow, amazing!
    - deleted 4y ago
      [deleted]

There’s always a <strike>bigger</strike> smaller <strike>fish</strike> particle.

by fooker 4y ago

There’s always a <strike>bigger</strike> smaller <strike>fish</strike> particle.

bawolff 4y ago

From my understanding, medium sized particles are actually the most expensive to filter

fooker 4y ago
What's the intuition behind this?
- LaputanMachine 4y ago
  Multiple physical effects are responsible for filtering. Each of them works best at certain particle diameters. The combined efficiency of all effects happens to have a minimum at 0.3 microns. [1] This is called the "Most Penetrating Particle Size" (MPPS). For very small particle sizes, filtering mostly works by diffusion (quoting from [2]): >[Diffusion] is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 μm in diameter. The small particles are effectively blown or bounced around and collide with the filter media fibers. This behavior is similar to Brownian motion and raises the probability that a particle will be stopped [...] [1]: https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_Collection_Mechanisms-en.svg https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_C... [2]: https://en.wikipedia.org/wiki/HEPA#Mechanism https://en.wikipedia.org/wiki/HEPA#Mechanism
  - schiffern 4y ago
    In the paper[0] they define "ultrafine emissions" as <0.1 microns. "Diesel Oxidation Catalyst (DOC) and Diesel Particle Filter (DPF) has been very effective in controlling the emissions of solid particles and hence BC, but that there has been little change in the liquid mode (<30 nm) particles, and that concentrations of ultrafine particles (<100 nm) still well exceed the threshold for “high” concentrations (>10e4 cm^−3 /24-hour mean) defined by WHO. BC declined by 81% between 2014 and 2021, but the ultrafine particle (<100 nm) count declined by only 26%. Looks like DPF/DOC filters use mainly interception, but they're not terribly effective at filtering via the diffusion mechanism. [0] https://www.sciencedirect.com/science/article/pii/S0160412023001617 https://www.sciencedirect.com/science/article/pii/S016041202...
- jodrellblank 4y ago
  See: https://dynomight.net/ikea-purifier/ https://dynomight.net/ikea-purifier/ Scroll down to “The physics of air purifiers seem simple.” for the relevant bit.

maxbond 4y ago

Y̵o̵u̵ ̵c̵a̵n̵ ̵a̵l̵s̵o̵ ̵u̵s̵e̵ ̵U̵n̵i̵c̵o̵d̵e̵ ̵s̵t̵r̵i̵k̵e̵t̵h̵r̵o̵u̵g̵h̵ ̵c̵h̵a̵r̵a̵c̵t̵e̵r̵s̵

fooker 4y ago
It's discouraged here for the sake of accessibility. Screen readers and translators don't do well with these characters.
- maxbond 4y ago
  Interesting. Thanks.
- moffkalast 4y ago
  As a test I've pasted that into ChatGPT asking it to edit it so it uses corresponding letters from the ASCII table and it removed the strikethrough flawlessly. Probably won't be an issue for those screen readers for much longer.
  - fooker 4y ago
    Wow, amazing!
  - deleted 4y ago
    [deleted]