General Radon Information

California specific radon and radon level information can be found throughout this site. You will be able to find information about certified radon inspectors in California, as well as detailed radon level information for every county in California.

Radon is one of the earth's natural elements. It is a colorless, odorless radioactive gas formed as a result of the radioactive decay of radium which, in turn, results from the decay of uranium. Most soils and rocks emit some radon although concentrations vary widely among towns and neighborhoods. Since it is a gas, radon can easily find its way out of rocks and soils, mix with other soil gases and enter homes and other buildings through cracks and openings in foundations. Some radon can also enter homes through drinking water supplies. Radon can then enter the air after leaving the water during showering, cooking, and other water use activities. Water from private wells may contain much higher levels of radon than public wells.

While California may have, on average, a small percentage of houses expected to have elevated radon it has a huge population. Also there are areas of high radon potential located in densely populated areas of the state. As a result some urban areas may have large numbers of houses with elevated radon levels.

Radon moves from uranium-bearing granite deposits in the soil to atmosphere because there is a lower concentration of radon in the atmosphere than in the soil. Your home is sited in its path and because the house is usually warmer than the surrounding soil, the air pressure is less and soil gases including radon move into the home. The most common routes are spaces between basement walls and slab, cracks in foundations and/or walls, openings around sump pumps and drains, construction joints, crawl spaces, and showers, etc using well water with high radon concentrations

Generally, radon is not a problem with public drinking water systems because during the water treatment process aeration releases dissolved radon to the atmosphere. However, if the water supply is from a private well, radon levels could be unacceptably high. The recommendation is to test the well water if the air radon concentrations in the occupied dwelling are over 4pCi/l. If you have tested the air in your home and found a radon problem and your water comes from a private well, you should test the water. (Look in the yellow pages for a lab certified to measure radiation in water.)

The Indoor Radon Abatement Act of 1988 directed the U.S. Environmental Protection Agency (EPA) to identify areas of the United States that have the potential to produce elevated levels of radon. EPA along with U.S. Geological Survey (USGS) and the Association of American State Geologists produced a series of maps and documents (EPA's Map of Radon Zones, CALIFORNIA 402-R-93-025). The maps of Radon Zones identify areas of each state that have the highest potential for elevated indoor radon levels (greater than 4 pCi/L) (California map, U.S. map). The maps were designed to assist national, State and local governments and organizations to target their radon program activities and resources and should not be used to determine radon levels of a given area or house within a particular county.

The California Radon Program along with California Geological Survey have been developing detailed radon potential maps for counties of the state. They have completed three such maps to date, Santa Barbara County, Ventura County and Southern Los Angeles County. The county maps clearly demonstrate that California has areas of high radon potential, contrary to some published information.

California Department of Health Services Radon Program with funding from the United States Environmental Protection Agency provides free radon test kits for residents of California. However the test kits are not to be used as part of a real estate transaction. California law requires professional providers of radon services to be certified. It is strongly recommended to hire a disinterested third to assure the validity of the testing. The State of California maintains a list of certified providers of radon services on this web page. Certified Radon Testers conduct radon measurements in residential structures, commercial structures, and occupational settings.

Do you want to test your home for radon? You can order your free test kit by one of the following:

1) Call the toll free radon message line 800-745-7236. Request the free Internet Test Kit and leave your Name, address, and phone number. Speak slowly and clearly and spell any difficult or unusual names. This is a message line only you will not be able to talk to anyone.

2) Call George Faggella 916-449-5674. He is usually at his desk. If he is not at his desk leave a short message and your phone number and he will return your call as soon as possible. You can also request the free Internet Test Kit just leave your name, address, and phone number and he will send you a test kit.

3) Email gfaggell@dhs.ca.gov write Free Internet Test Kit in the subject line, and send your name, address, and phone number.

Not sure which floor to test? That depends on whether you are testing your home for a real estate transaction or for your own purposes. If you are testing to determine if your home has radon levels warranting mitigation, the EPA recommends testing in the lowest living area of your home. For a real estate transaction, EPA recommends testing in the lowest area which could be modified to become a living area.