Quality Assurance & Quality Control
Introduction to Radon Mitigation
Worker Health & Safety
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Passive Sub Slab Depressurization (SSD)

In homes with basement or slab-on-grade foundations, the following components of a passive SSD design must be installed during construction in Illinois:

Option I – Suction pit with “T” Pipe

  • A minimum 3-inch diameter Schedule 40 PVC must be embedded vertically into the sub-slab aggregate or other permeable material before the slab is cased.
  • A “T” fitting or equivalent method must be used to ensure that the pipe opening remains within the sub-slab permeable material.
  • Alternatively, the 3-inch pipe must be inserted directly into an interior perimeter drain tile loop. The vent pipe must be extended up through the building floors, terminate at least 12 inches above the highest roof in a location at least 2 feet above any window or other opening into the conditioned spaces of the building and 10 feet from any window or other opening in adjoining or adjacent buildings.

Option II – Cored Suction Point [preferred]

  • A penetration into the sub-slab permeable material may be cored through sub-slab after the slab is cased
  • A minimum 3-inch diameter Schedule 40 PVD embedded vertically into the sub-slab aggregate or other permeable material
  • Must extend up through the building floors
  • Must terminate at least 12 inches above the penetration in the highest roof
  • Must terminate in a location at least 2 feet above any window or other opening into the conditioned spaces of the building
  • Must terminate at least 10 feet from any window or other opening in adjoining or adjacent buildings
  • In buildings where interior footings or other barriers separate the sub-slab aggregate or other gas-permeable material, each area must be fitted with an individual vent pipe
  • Vent pipes must connect to a single vent that must terminate:
  • At least 12 inches above the highest roof in a location
  • At least 2 feet above any window or other opening into the conditioned spaces of the building and
  • 10 feet from any window or other opening in adjoining or adjacent buildings
  • All components of the radon vent pipe system must be installed to provide positive drainage to the ground beneath the slab or soil gas retarder
  • Radon vent pipes must be accessible for fan installation through an attic or other area outside and above the habitable space. The radon vent pipe need not be accessible in an attic space when an approved roof-top electrical supply is provided for future use.