How To Look At A House
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Do I need a radon test for a house with a radon mitigation system?
Monday, March 23, 2020
Unfortunately, the fact that a house already has a radon mitigation system does not guarantee that the radon level in the home is below the Environmental Protection Agency (EPA) maximum for indoor air of 4.0 pCi/L (pico curies per liter of air). So a homebuyer should go ahead and test to be sure. Here’s three reasons why the indoor radon level may have risen since the system was installed:
1) A mitigation system uses a fan to pull the radon from the ground to a pipe that extends above the roof to keep it from entering the home. The fan’s cfm (cubic feet per minute of air flow) may have deteriorated if it is older, or the fan may no longer even be functional.
A simple way to check if the fan is functioning at all is to check the manometer that is required to be installed as part of the system. A manometer is a U-shaped tube on the side of the exhaust pipe at eye level filled with a colored liquid. It is usually located in the corner of a closet in a Florida house, or in the basement of northern house. When the exhaust fan for the radon mitigation system is operating, the air suction will cause the column to rise on one side, and the tube will have inch markings on it so that a viewer can check the number of inches of differential between the equilibrium point of the twin columns in the U-shaped tube. An example is shown below of mitigation system piping installed in a bedroom closet.
2) The fact that a manometer verifies that the fan is functioning, does not mean everything is alright. Most radon mitigators guarantee to get the indoor air below 4.0 pCi/L when their work is done; but, if the flow of radon from the ground has gone up since installation, the system as installed may not be able to keep up with the higher radon emissions.
3) Also, the EPA standard for any radon system is to check the radon level every two years anyway, and that is not often done by homeowners. So it probably hasn’t been tested in a while.
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