“There
are four mechanisms at work: capture by straining, impaction, interception, and
diffusion. Straining/sieving is defined as when a particle is too large and
becomes trapped between two filter fibers. Impaction is when a particle of
relatively greater mass is unable to follow the curved streamline around the
fiber and, as a result of momentum, travels in a straight line into the filter
fiber and sticks. Interception occurs when a section of a particle “runs into”
a filter fiber. Diffusion capture occurs when particles leave the streamline
due to random collisions with the surrounding fluid molecules and strike the
fibers, where they again stick.”
The
above text is from an on-line article introducing HEPA filters by Jason Kelly
for Controlled Environments.
Posted by Tim Sandle
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