General Radon Information

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

Radon is an invisible, radioactive gas created from natural deposits of uranium and radium in the soil. Uranium breaks down to radium, which in turn decays into radon gas. Radon is an inert gas, which means it does not react or combine with the elements in the ground. Because of this, radon can move up through the soil into the atmosphere, where radon is easily diluted and presents little concern. However, when radon enters a building from the soil below, it can accumulate and become a health concern.

Radon gas can be drawn into a building and accumulate to concentrations that can increase the potential for contracting lung cancer. In some rare cases, building materials that contained by-products of uranium processing have been a source of radon in other states; but most of the radon in Arizona homes comes from the natural deposits of uranium commonly found in Arizona soils and rocks. Unlike some other environmental concerns, elevated indoor radon is seldom caused by human intervention. Radon enters a building through its foundation, basement, crawlspace, or slab floor. As the radon rises inside the building, it is diluted with air that leaks through exterior walls and other openings. Consequently, radon levels are typically highest in the lowest portion of the home. If a test is conducted in the lowest level of the home suitable for occupancy, with all the exterior doors and windows closed, the home's owner or prospective buyer can be reasonably assured that exposures to radon in upper portions of the home are less than in the lower levels. It can also be assumed the indoor radon exposure would be less when fresh outdoor air is allowed into the home.

According to a national residential radon survey completed in 1991, the average indoor radon level in the United States is 1.3 picocuries per liter (pCi/L). The average outdoor level is about 0.4 pCi/L. However, not all houses or buildings--even those in the same area or the same neighborhood--have the same radon level. The only way to find out what the radon level is in your house is to test for it.

Short-term tests take 60 hours to complete. The house is closed for 12 hours, then the test instrument is activated or opened and left in place for 48 hours or more.Long-term tests take more than 91 days to complete and are conducted with the house in a normal living mode. Alpha track detectors or electronic detection instruments are used. Long-term test results give a more representative picture of the true radon levels in the home over time as fluctuations due to changes in ambient temperature and barometric pressure are detected and factored into the final valuation.

If a test indicates an elevated level of radon, reducing the level is usually easy and inexpensive. Sometimes homeowners can do the work themselves, although it is recommended that they seek professional guidance or have the work done by a professional, EPA-certified radon mitigator.

Results from the state indoor radon sampling survey conducted 1987-89 by the Arizona Radiation Regulatory Agency suggest that about 1 out of 15 Arizona homes may contain radon concentrations in excess of the EPA recommended action level of 4.0 picocuries per liter of air (4.0pCi/L). That rate is similar to the national average. However, Arizona's warm temperate climate can result in a lower thermal suction on the soil beneath homes than is typically found beneath houses situated in a more northward latitude. Thus, even though radon is present, less may be drawn into a home here than in a comparable home in many other states.

Various mitigation techniques are available to reduce indoor air radon concentrations. Homes with radon levels in excess of the 4.0 pCi/L (action level) but less than 7 pCi/L may be temporarily corrected by sealing cracks and openings in the foundation. Please note: Sealing cracks is a temporary solution until the home can be mitigated by a qualified contractor. Most homes can be successfully mitigated with a technique known as sub-slab depressurization. This system utilizes four inch PVC piping and a special fan to collect and transport soil gases including radon from under the foundation and exhaust them above the roof eave. There are a number of other mitigation techniques available for use in different home construction styles.