Re: Bag house?

["Rebecca Leighton Katers" <cwac@execpc.com>]

  A baghouse is a large piece of pollution control 
  equipment.   The gases and dust coming out of a 
  smoke stack are passed through this bag, which 
  operates like a huge vacuum cleaner bag.
  
  The walls of the bag are slightly porous, 
  allowing the gases to escape, but not the larger 
  particles of dust.   
  
  As the dust accumulates on the bag, its 
  cleaning efficiency increases initially, but then 
  it gets clogged.
  
  At that point, the bag is shaken or scraped to 
  reduce the clogging.   The dust falls to the 
  bottom to be collected and removed.
  
  The bag has a limited life, and has fluctuating 
  periods of ineffectiveness when it is too clean, clogged or 
  being rejuvenated.
  
  Some emissions are "stickier" and more prone to 
  clog the bag, reducing it's effectiveness.
  
  Some gases are partially trapped as they get 
  stuck to dust particles in the bag.   Some 
  gases condense into a liquid as they cool down 
  before leaving the bag.
  
  Super-fine particles, like those EPA proposes to 
  regulate now, often pass through the baghouse --- 
  which means that the most dangerous particles are 
  not being collected.
  Rebecca Leighton Katers
  Clean Water Action Council of N.E. Wisconsin
  2220 Deckner Avenue
  Green Bay, WI 54302
  Phone:  414-468-4243
  Fax:  414-468-1234
  E-mail:  cwac@execpc.com