• How Radon Enters Your House

Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil, rock, and water. Air pressure inside your home is usually lower than pressure in the soil around your home's foundation. Because of this difference in pressure, your house acts like a vacuum, drawing radon in through foundation cracks and other openings. Radon may also be present in well water and can be released into the air in your home when water is used for showering and other household uses. In most cases, radon entering the home through water is a small risk compared with radon entering your home from the soil. In a small number of homes, the building materials (e.g., granite and certain concrete products) can give off radon, although building materials rarely cause radon problems by themselves. In the United States, radon gas in soils is the principal source of elevated radon levels in homes.

how radon enters your house

Figure 175: Air pressure inside your home is usually lower than pressure in the soil around your home's foundation. Because of this difference in pressure, your house acts like a vacuum, drawing radon in through foundation cracks and other openings.


  • Radon is a Cancer-causing, Radioactive Gas

Radon is estimated to cause many thousands of lung cancer deaths each year. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States.  Only smoking causes more lung cancer deaths. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.

  • What Do Your Radon Test Results Mean?

Any radon exposure has some risk of causing lung cancer. The lower the radon level in your home, the lower your family's risk of lung cancer.  The amount of radon in the air is measured in "picoCuries of radon per liter of air, " or "pCi/L. "  Sometimes test results are expressed in Working Levels, "WL," rather than picoCuries per liter of air.  A level of 0.02 WL is usually equal to about 4 pCi/L in a typical home.

The U.S. Congress has set a long-term goal that indoor radon levels be no more than outdoor levels; about 0.4 pCi/L of radon is normally found in the outside air.  EPA recommends fixing your home if the results one long-term test or the average of two short-term tests show radon levels of 4 pCi/L (or 0.02 WL) or higher.  With today's technology, radon levels in most homes can be reduced to 2 pCi/L or below.  You may also want to consider fixing if the level is between 2 and 4 pCi/L.

A short-term test remains in your home for 2 days to 90 days, whereas a long-term test remains in your home for more than 90 days.  All radon tests should be taken for a minimum of 48 hours.  A short-term test will yield faster results, but a long-term test will give a better understanding of your home's year-round average radon level.

The EPA recommends two categories of radon testing.  One category is for concerned homeowners or occupants whose house is not for sale.  The second category is for real estate transactions.

  • Why Hire a Contractor?

EPA recommends that you have a qualified radon mitigation contractor fix your home because lowering high radon levels requires specific technical knowledge and special skills. Without the proper equipment or technical knowledge, you could actually increase your radon level or create other potential hazards and additional costs. However, if you decide to do the work yourself, get information on appropriate training courses and copies of EPA's technical guidance documents from the EPA web site and your State radon office.

  • Will Any Contractor Do?

EPA recommends that you use a State certified and/or qualified radon mitigation contractor trained to fix radon problems. You can determine a service provider's qualifications to perform radon measurements or to mitigate your home in several ways. First, check with your State radon office.  Many states require radon professionals to be licensed, certified, or registered, and to install radon mitigation systems that meet State requirements.  Most states can provide you with a list of knowledgeable radon service providers doing business in the State.  In states that don't regulate radon services, ask the contractor if they hold a professional proficiency or certification credential, and if they follow industry consensus standards such as the American Society for Testing and Materials (ASTM) Standard Practice for Installing Radon Mitigation Systems in Existing Low-Rise Residential Buildings, E2121 (March 2001), or the U.S. EPA's Radon Mitigation Standards (EPA 402-R-93-078, revised April 1994).  You can contact private proficiency programs for lists of privately-certified professionals in your area.  Such programs usually provide members with a photo-ID, which indicates their qualification(s) and the ID-card's expiration date.  For more information on private proficiency programs, visit www.epa.gov/radon/proficiency.html, or contact your State radon office.

  • Selecting a Radon Test Kit

Since you cannon see or smell radon, special equipment is needed to detect it.  When you're ready to test your home, contact your State radon office (or visit www.epa.gov/radon/proficiency.html) for information on locating qualified test kits or qualified radon testers.  You can also order test kits and obtain information from a radon hotline. There are two types of radon testing devices.  Passive radon testing devices do not need power to function. These include charcoal canisters, alpha-track detectors, charcoal liquid scintillation devices, and electret ion chamber detectors.  Both short- and long-term passive devices are generally inexpensive.  Active radon testing devices require power to function and usually provide hourly readings and an average result for the test period.  These include continuous radon monitors and continuous working level monitors, and these test may cost more.  A State or local official can explain the differences between devices and recommend ones which are more appropriate for your needs and expected testing conditions.  Make sure to use a radon testing devices from a qualified laboratory.