Checking HEPA filters?

[Steve Carpenter - Cascade Research Assoc.]

A dry-ice fogger to check for airflow distribution within any HEPA filter 
system:

1. Purchase a 2' length of 4" diameter plastic pipe.  I use ABS sewer
   pipe.  Close off one end, being sure to use glue to make it watertight,
   and thread the other end so that you can place a screw-on cap on it. 

2. Fit the side of the pipe with a plastic or metal tapered pipe fitting
   over which you can place a 1/2-5/8" diam, 2-3' length of flexible, clear 
   tubing.

3. When you are ready to test, open the cap and put about a half quart to
   a quart of hot water.  Throw in a good chunk of dry ice.  Screw on the
   cap.

4. Presto! - out comes fog through the clear tubing in the side of the 
   pipe.
 
  You can the use the fog in the chamber to see if the air is blowing 
properly.  If you can access the plenum area above the filter, you may be 
able to see leaks through large holes, depending on conditions.

I have use this apparatus to successfully test many HEPA units in cleanrooms.

-Steve Carpenter, Ph.D.
 Cascade Research Associates
  & Abbey Lane Laboratory
 microbe at pioneer.net