Opinion

  1. Ed Hodgkins Ed Hodgkins United States says:

    Smaller particles are affected more so by Brownian motion and are more apt to be captured by nearby thread.  It is therefore logical that the mask would capture smaller objects more efficiently.  None of these things measuring as small as nanometers travel in a directly line.  There are a lot of forces at work.

    • Ken Largent Ken Largent United States says:

      So what I hear from you is that small round pegs are blocked by big square holes better because small round pegs don't travel in straight lines.

      What I gather from the article is that filter material intended to block "most" particles of a certain size are assumed to be effective against particles that are 2,000 times smaller.  Under his flawed logic, the material we use to keep flies out of our houses would also make great insulation material against the cold.

      Here is reality:  a filter material that is effective against particles of a certain size cannot be as effective against particles 2,000 time smaller.

      Even though there are masks capable of filtering out smoke particles, firefighters still use an oxygen source instead of masks because masks do not create oxygen in an oxygen depleted atmosphere AND there are other toxins besides smoke in a typical fire that a mask cannot filter out.

      The math says that particles that are 2,000 times smaller than the targeted substance are 200 times MORE likely to pass through the filter material than the "acceptable" 5 percent.

      • Greg Phillips Greg Phillips Canada says:

        The theory refers to particles that are 1/10th of a micron. Material used to keep flies out of our houses is about 20,000 times larger.

      • Greg Phillips Greg Phillips Canada says:

        Google it. Robert Brown. Brownian Theory of Motion. Larger particles have the mass to follow an airstream and flow in straight lines. Smaller particles don't have the mass and therefore they zig-zag around instead of following the airstream, and don't move in straight lines. They get bounced around and that is why they are easier to capture than larger particles that move in straight lines.

        • Carlo Wood Carlo Wood Netherlands says:

          They bounce against air molecules, causing them to have an effective diameter larger than their real diameter. However, the effective diameter is at all times LESS than that of a particle with a (slightly) larger diameter. The net result is that smaller particles get captured LESS often. The Brownian motion might cause them to be captured  more often than what would be the case in a vacuum, it is still much much less than 95%. Lets say their effective diameter becomes 10x larger (which I doubt) then the holes are still 200 times larger and they'll fly through with the air unimpeded.

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