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indoor radon program

Fixing a Radon Problem - Fix My House

Indoor radon levels can be reduced by installing a relatively simple system. You can do it yourself if you are handy or hire a Certified Radon Mitigator.

There are two common configurations of the basic system, one for slab-on-grade and basement homes and one for raised foundation homes. The following are excerpts from the US EPA's Consumer's Guide to Radon Reduction.

Action Sub-Slab Suction


Active Sub-slab suction (also called sub-slab depressurization)  is the most common and usually the most reliable radon reduction method. One or more suction pipes are inserted through the floor slab into the crushed rock or soil underneath. They also may be inserted below the concrete slab from outside the house. The number and location of suction pipes that are needed depends on how easily air can move in the crushed rock or soil under the slab, and on the strength of the radon source. Often, only a single suction point is needed.

Sub-Membrane Suction

An effective method to reduce radon levels in crawlspace houses involves covering the earth floor with a high-density plastic sheet. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. This form of soil suction is called sub-membrane suction, and when properly applied is the most effective way to reduce radon levels in crawlspace houses.

Active Crawlspace Depressurization (a less favorable option)

A less-favorable option is active crawlspace depressurization which involves drawing air directly from the crawlspace using a fan. This technique generally does not work as well as sub-membrane suction and requires special attention to combustion appliance back drafting and sealing the crawlspace from other portions of the house, and may also result in increased energy costs due to loss of conditioned air from the house.

Checking Your Contractor's Work

Below is a list of basic installation requirements that your contractor should meet when installing a radon reduction system in your home.  It is important to verify with your contractor that the radon mitigation standards are properly met to ensure that your radon reduction system will be effective. Ask your contractor for a written guarantee that the installed radon system complies with the current accepted standard practice for installing radon mitigation systems in existing low-rise residential buildings (ASTM E 2121-03).

  • Radon reduction systems must be clearly labeled. This will avoid accidental changes to the system which could disrupt its function.
  • The exhaust pipe(s) of soil suction systems must vent above the surface of the roof and 10 feet or more above the ground, and at least 10 feet away from windows, doors, or other openings that could allow the radon to reenter the house, if the exhaust pipe(s) do not vent at least 2 feet above these openings.
  • All vent stack piping shall be solid, ridged pipe not less than 3 inches inside diameter.
  • The exhaust fan must not be located in or below a livable area. For instance, it should be in an unoccupied attic of the house or outside - not in a basement!
  • If installing an exhaust fan outside, the contractor must install a fan that meets local building codes for exterior use.
  • Electrical connections of all active radon reduction systems must be installed according to local electrical codes. 
  • A warning device must be installed to alert you if an active system stops working properly. Examples of system failure warning devices are: a liquid gauge, a sound alarm, a light indicator, and a dial (needle display) gauge.  The warning device must be placed where it can be seen or heard easily. Your contractor should check that the warning device works.  Later on, if your monitor shows that the system is not working properly, call a contractor to have it checked. 
  • A post-mitigation radon test should be done within 30 days of system installation, but no sooner than 24 hours after your system is in operation with the fan on, if it has one.  The contractor may perform a post-mitigation test to check his work and the initial effectiveness of the system; however, it is recommended that you also get an independent follow-up radon measurement.  Having an independent tester perform the test, or conducting the measurement yourself, will eliminate any potential conflict of interest.  To test the system's effectiveness, a 2-7 day measurement is recommended.  Test conditions:  windows and doors must be closed 12 hours before and during the test, except for normal entry/exit. 
  • Make sure your contractor completely explains your radon reduction system, demonstrates how it operates, and explains how to maintain it.  Ask for written operating and maintenance instructions and copies of any warranties.

Complaints about Radon Services

If you feel the service was not in accordance with Mitigation or Testing Standards, contact CDPH's Indoor Radon Program.   Program staff will assist you in submitting a formal complaint to either the National Radon Proficiency Program (NRPP) or National Radon Safety Board (NRSB).

Do It Yourself?

If you are interested in fixing the radon problem in your home yourself, check your local library or go online to purchase a copy of "Protect Your Home From Radon: A Step-by-Step Manual For Radon Reduction" Second Edition, D.L Kladder with Dr. J. F. Burkhart and S.R. Jelinek, which is designed for the do-it-yourselfer.

Radon Program

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