Unit Activity

Review the information about the house below.

View the illustration of the house depicting a house with a combination sub-slab, sub-membrane, and block wall depressurization.

Answer the activity questions.

House Information Before Mitigation

• You have sealed all visible cracks and opening.
  
  
• The crawl space and sump have been covered and sealed properly.
  
  
• You remembered to install a means of surface water relief into the sump because no floor drains were present.
  
  
• You mitigated this home based on the one test conducted by the homeowner, (it failed, what was the point of testing the slab.)
  
  
• After installing the system you gave the homeowner two test kits, one for the basement and one for the family room on the slab.
  
  
• Post mitigation results: Basement- 8.1 pCi/l, Family room slab- 1.3 pCi/l.
  
  
• Upon further inspection and diagnostics using a smoke stick you find the following.
  
  
• You seem to have a pressure field extension under the entire basement floor. The smoke test at the farthest point from the suction hole is poor, but there is some suction. The material you removed from below the basement floor was pea gravel.
  
  
• Smoke tests indicate the crawlspace also has adequate but low suction below the membrane.
  
  
• The block wall adjacent to the garage has good suction. The block wall adjacent to the crawl has some suction.
  
  
• The block wall on the front of the home and adjacent to the slab have no visual air movement that you can tell from your smoke tests.
  
  
• The U-tube manometer is reading 0.2" WC (water columns).
  
  
• The fan you used is capable of moving 150 cfm (cubic feet per minute) of air at 0" WC , 110 cfm at .75" WC, and 38 cfm at 1.5" WC.
  
  
• This is the only diagnostic equipment you have and must make a choice on how to proceed based on the above information.

Copyright 2000, Great Lakes Center for Occupational & Environmental Safety & Health, School of Public Health, University of Illinois at Chicago