Introduction to Radon & Health Risk
The Fundamentals of Radon & Radioactivity
Radon Occurrence & Behavior
Radon Measurement & Devices
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Additional Radon Pathways

The following foundation openings may allow soil gas to bring in radon:

  • The opening between the basement and crawl space.
  • Cracks in concrete slabs and walls.
  • Sump holes (may be connected to earth, gravel drainage, perimeter drain pipes, waterline, or a variety of other transport paths).
  • Floor drains (connected as above).
  • Holes through slabs under tubs, showers, or toilets where space was left around traps.
  • Holes in the slab around pipes.
  • Heating ducts run under slabs.
  • Pores, cracks, gaps in mortar, and open tops in concrete block walls.
  • Holes in slabs where wooden stair stringers or pieces of blocking penetrate the slab.
  • Cracks in slab around support columns.
  • Support walls for fireplaces.
  • Cracks at the wall joint in a basement (especially the perimeter expansion joints and canal drains).
  • Cracks around water, gas, and utility entry lines.

Figure 3-21 illustrates radon entry into buildings by transport mechanisms and pathways that typically facilitate radon entry.

Figure 3-21
Radon Entry Routes
Source: EPA
  • A) Cracks in concrete slab
  • B) Cracks between poured concrete & blocks
  • C) Pores & cracks in concrete blocks
  • D) Slab-footing joints
  • E) Exposed soil, as in sump
  • F) Weeping tile
  • G) Mortar joints
  • H) Loose fitting pipes
  • I) Granite
  • J) Water