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• #239 nuke7 veterán Reggie0 #238

  Új Válasz 2020-04-02 16:27:08 #239

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  nuke7

  veterán

  válasz Reggie0 #238 üzenetére

  hát... nem városi legenda :
  (bocsánat, azért a 0.3-nál mérik, mert azt a legnehezebb elkapni )
  
  But when we get to really small particles – like particles under 0.3 microns, things start getting weird. Particles that small have so little mass that they actually get bounced around like a pinball when they hit gas molecules (known as Brownian Motion). So they move in random zigzag patterns.
  
  
  
  These tiny particles are small enough to fit through HEPA filters if they flew straight. But because they fly in zigzag patterns, they end up hitting the fibers and getting stuck.
  Here’s why that 0.3 micron number comes up all the time. The weirdness of Brownian motion works its magic under 0.3 microns. The more easily understandable filtering works its magic above 0.3 microns. But where those two processes overlap is the weak spot. Particles at 0.3 microns lie in between the two, and that makes them the hardest particle size to capture. Researchers call this the most penetrating particle size (MPPS).

  https://en.wikipedia.org/wiki/Brownian_motion

  https://smartairfilters.com/en/blog/what-is-pm0-3-why-important/

  Is There Any Actual Evidence that HEPAs Capture Tiny Particles?
  Scientists from NASA have tested the particle capturing efficiency of filters and found that 0.3 microns is the lowest point. Another piece of evidence comes from hospitals and airplanes, many of which use HEPAs to capture viruses as the “removal efficiency is generally greater for particles both larger and smaller” than 0.3 microns.
  
  
  
  The theory of 0.3 microns being hardest to capture works for fiber filters of all types, including masks and lower-grade MERV furnace filter.

  https://youtube.com/user/nuke7

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