You can take steps to reduce and control the amount of radon in your home. Testing is the only way to determine radon levels. Have your home tested by a professional. EPA guidance suggests mitigating if levels are at or above 148 Becquerels/meter3 (4 picocuries/liter).
The effectiveness of any one radon-reduction method will depend upon the unique characteristics of your home, the level of radon, how it is getting into your house, and how thoroughly the job is done. A single method may do the job, but sometimes a combination of several methods must be used.
Homes are generally categorized according to their foundation design: basement, slab-on-grade, or crawlspace. Some homes have more than one foundation design feature: a basement under one part of the home and a slab-on-grade or crawlspace in another area. In these situations a combination of radon-reduction techniques may be needed to reduce radon levels to below the Canadian guideline.
A certified radon professional will likely perform one or more diagnostic tests to help determine the best radon-reduction system for your home. For example, your contractor may use chemical smoke to see the air flow sources and radon entry points by watching a small amount of smoke that has been placed into holes, drains, sumps or along cracks. Another type of diagnostic test is a Pressure Field Extension Test (or communication test). This test uses a vacuum cleaner (e.g., a Shopvac) to measure how easily air can move from one point to another under the foundation and estimate the number of suction points and fan size needed for an active radon-reduction system.
Sub-slab depressurization (also called active soil depressurization) is the most effective and reliable radon reduction technique. It is also the most common method used by C-NRPP certified professionals. This method involves installing a pipe through the foundation floor slab and attaching a fan that runs continuously to draw the radon gas from below the home and release it into the outdoors where it is quickly diluted. This system also reverses the air pressure difference between the house and soil, reducing the amount of radon that is drawn into the home through the foundation. One, or sometimes multiple, suction points are inserted through the floor slab into the crushed rock or soil underneath to effectively reduce the radon level in the home.
The sub-slab depressurization pipe can be vented at either the roof level or ground level of the home. The fan can be placed in the basement or an area outside of the living space such as in a garage or attic. If the fan is placed inside the living space of the home, it is usually vented sideways through the rim joist at ground level, with the fan close to the exhaust location. When the fan is placed outside of the living space (e.g. attic or garage) then it is typically vented upwards above the roof.