What Do My Radon Test Results Mean?

According to the US Environmental Protection Agency, “Any radon exposure has some risk of causing lung cancer”. Smokers who are exposed to radon are at even greater risk. The EPA estimates that approximately 21, 000 lung cancer deaths /year can be attributed to radon exposure.

Results from radon testing is reported in PCi/L (picocuries/liter). To help make sense of these measurements and understand the risks of radon exposure consider these comparisons:

Radon level of 4 pCi/L

  • Cancer risk at this level is comparable to smoking 8 cigarettes/day
  • Cancer risk at this level is comparable to approximately 200 chest x-rays/year

Radon level of 15 pCi/L

  • Cancer risk at this level is comparable to smoking 1 pack of cigarettes/day.


It’s important to note that radon levels will fluctuate throughout the year and can be influenced by weather. Wind, storms and temperature changes can increase or decrease radon concentrations. Some reasons for these fluctuations include:

  • Period of rain can “seal” the soil surface forcing radon gas into a building
  • A chimney effect inside a home during winter heating pulls soil gas into lower levels of the house.
  • Well sealed and insulated homes decrease ventilation allowing radon gas build up.
  • Frozen soil restricts gas movement to areas of less resistance (foundation openings)

Overall, radon levels tend to run higher during the winter. A long term test is suggested when levels hover around 4 pCi/l to get a better picture of overall annual exposure. However, the EPA has established 4.0 pCi/l as the action level for radon mitigation.

In general, radon levels will be highest in the lowest level of the home, the level with the most contact to soil. Consider your family’s activities in regard to radon mitigation. If the lowest level of your home is used for exercise, a family room, or children’s play area, radon levels of 4.0 or higher should be definitely addressed.

Radon testing is recommended for all Pennsylvania residents. It is estimated that over 40% of all Pennsylvania homes contain radon levels above the EPA “safe” limit of 4.0 pCi/L.

About the Author

Katherine Fisher is the co-owner and Vice President of SWAT Environmental of Pennsylvania. She holds a Bachelors degree from Purdue University in Environmental Sciences and is NRPP certified in radon measurement and radon mitigation. For more information on radon or radon mitigation, contact SWAT Environmental of Pennsylvania at 1-800-NO-RADON or www.radon-pennsylvania.com

on 18 November 2016
Hits: 3896