• Floor has to be well sealed to reduce loss of interior and backdrafting potential.
• Dampers should be used to adjust air flow rates to the point that smoke is barely drawn down through flooring. Disable dampers.
• Note that at this time the RMS allows a discharge near grade level, but raising it may be helpful.

Labeling & Indicators for Crawl Space Depressurization Systems

• Place label on access to crawl space, warning occupant or future occupant that if the floor is cut significant amounts of interior air could be lost and that the fan should be shut off first.
• Label electrical panel as well.
• Excess air flow indicator would be prudent.

Results from Sealing and Depressuring Crawl Spaces

Note that even though crawl space radon went up, the living space concentrations went down.

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