> The filter in an envirocaire is a true HEPA filter - doubt that is 
 > what
 > anyone uses in their cars.
 > 
 > The outer filter is only a charcoal prefilter - catches the first 
 > wave
 > of cockatoo dust and turns white.  Beating on the nearest tree trunk
 > removes lots of the dust (looks almost black again) and gives the
 > impression you are starting over.
I can tell you're not a "tree hugger."  I have the Black and Decker 
envirocare air cleaners, and I vacuum the prefilter on a regular basis. I 
tried washing it once, but I'm sure it lost its effectiveness. The charcoal 
filters are pretty expensive for someone who might have lots of dusty birds 
(such as me! with my cockatiels, greys and cockatoos) so we have to do all we 
can to prolong the filters' lives!
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