Answer to Question #10041 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Radon

The following question was answered by an expert in the appropriate field:


We have a radon mitigation system installed in our home. However, the exhaust end of the system is above the roof about 38 centimeters (cm) and right above our master-bed window about 0.6 meters (m). We are afraid that the exhausted gas will come through the window and back to the master bed. Please give us some guideance on this.


According to the U.S. Environmental Protection Agency (EPA), a soil suction system must be designed so that the the exhaust pipe vents meet all the following requirements:

  • Vents must be above the roof surface.
  • Vents must be 3 m or greater above the ground.
  • If vents are not at least 0.6 m above windows, doors, or other openings that could allow radon to reenter the home, they must be at least 3 m away from such openings.

For your case, the vent pipe is 38 cm above the roof and directly above the bedroom window. In order to meet the guideline of 0.6 m above the opening, the upper end of the window opening would have to be at least 23 cm below the roof. If not, you could meet the EPA guideline by having the pipe extended so that it was at least 0.6 m above the top of the window opening. If you are still concerned, even if the pipe meets the EPA guideline or after you modify it to do so, you could perform another radon test on your house, being sure to include the bedroom in question.

Thomas Gesell, PhD

U.S. Environmental Protection Agency. Consumers guide to radon reduction. Available at:

Answer posted on 9 February 2012. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.