Radon Testing

Radon Testing in Colorado


  • Radon is a naturally occurring radioactive gas that comes from the breakdown of uranium in the soil.
    • It’s a gas that moves up through the soil to the atmosphere.
  • ​High radon levels have been found in all 50 states and in all parts of Colorado.
  • In Colorado, about half the homes have radon levels higher than the U.S. Environmental Protection Agency recommended action level of 4 picoCuries per liter (pCi/L):


How radon gets into your home

  • Radon moves from uranium-bearing granite deposits in the soil to the atmosphere.
    • Your home sits on radon’s pathway from the soil to the atmosphere.
    • Your home is usually warmer and has lower air pressure than the surrounding soil, so gases in the soil, including radon, move into your home.
    • The most common routes are:
      • Spaces between basement walls and the slab.
      • Cracks in foundations and/or walls.
      • Openings around sump pumps and drains.
      • Construction joints and plumbing penetrations.
      • Crawl spaces.
      • Well water with high radon concentrations.
  • ​​The age and/or type of home doesn’t matter when it comes to whether high levels of radon are present.


How to test

  • The best place for testing radon levels depends whether you’re testing your home for a real estate transaction or for your own purposes:
    • If you’re testing to determine whether your home has radon levels warranting mitigation, the EPA recommends testing in the lowest living area of your home.
    • For a real estate transaction, the EPA recommends testing in the lowest area that could be modified to become a living area.


Reducing radon levels

  • The most effective solution is usually a sub-slab (or if you have a crawl space, sub-membrane) depressurization system.
  • A mitigation system in Colorado usually costs about $800-$1,200 unless difficult design problems are encountered.
  • You might be able to do sub-slab depressurization yourself if you have good handyman skills, including electrical wiring skills.
  • ​​While caulking and sealing are done as part of the mitigation process, the purpose isn’t to keep radon out but to hold conditioned air in.
    • It’s impossible to seal all cracks and the task is time-consuming, expensive and temporary (sealant dries out over time).
    • This procedure isn’t recommended as a stand-alone technique.


Short-term vs. long-term tests

  • Short-term tests take 48-120 hours to complete:
    • The house is closed for 12 hours, then the testing device is activated or opened and left in place for 48 hours or more.
    • Charcoal canisters are generally used, although electronic instruments may also be used.
  • Long-term tests take 91 days to one year to complete and are conducted with the house under normal living conditions:
    • Alpha-track detectors or electronic detection instruments are used.
    • Long-term test results give a more representative picture of the true radon levels in the home over time, as fluctuations due to changes in ambient temperature and barometric pressure are detected and factored into the final average.