Answer to Question #12305 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
We had a high radon level. We installed a mitigation system with a vent pipe on the roof about 5 meters (m) above the ground. The vent pipe is directly above the garage and outdoor courtyard where we spend a lot of time in the summer. The roof line is about 3.5 m (at the gutter) above the courtyard, and the pipe vent exit is about 1.5 m above the gutter. So the exit point is about 4.5–5 m above ground level.
I am concerned that the radon will just flow down the roof line and into the courtyard and garage where my kids will inhale it while playing outside. Can you confirm if this is safe or if it should be relocated to the side of the home where no one hangs out?
This is an excellent question as radon system exhausts should be designed to prevent accidental exposure to anyone nearby and to prevent radon entry back into the building. The good news is that the exhaust point you describe as being 5 m above the ground definitely exceeds U.S. Environmental Protection Agency (EPA) and American National Standards Institute/American Association of Radon Scientists and Technologists (ANSI/AARST) minimum requirements if it is also 3 m from any air intakes, doors, or windows. Language regarding system exhausts typically found in radon mitigation standards suggest keeping the exhaust point at least 3 m off the ground and 3 m away from and 0.6 m above any opening back into the building or neighboring structures. These suggestions are summarized on page 12 of the EPA radon reduction guide.
The other good news is that the fan pushes the exhaust air upward out of the pipe about another 3 m, and along that path the radon-laden air is quickly diluted and dispersed. Although some people describe radon as being a heavy gas, it does not fall downward—each atom that is dispersed is far lighter than a dust particle.
Past President of AARST