General Radon Information

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

Radon is one of the natural elements present on earth. 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.

However, it is important to note that radon gas from soil is the primary source of radon in most homes. All homes and buildings contain some levels of radon. Radon concentrations can even be detected in outdoor air.

How does radon enter your home? Houses act like large chimneys. As the air in the house warms, it rises to leak out the attic openings and around the upper floor windows. This creates a small suction at the lowest level of the house, pulling the radon out of the soil and into the house. You can test this on a cold day by opening a top floor window an inch. You will notice warm air from the house rushing out that opening; yet, if you open a basement window an inch, you will feel the cold outside air rushing in. This suction is what pulls the radon out of the soil and into the house. You might think caulking the cracks and the openings in the basement floor will stop the radon from entering the house. It is unlikely that caulking the accessible cracks and joints will permanently seal the openings radon needs to enter the house. The radon levels will still likely remain unchanged. All houses should be tested for radon, if not during the sale or purchase, at least after you take occupancy. Even houses in areas of low radon potential can have elevated radon levels. The probability of course is less in low radon potential areas but it doesn't matter what the probability is if your house is the one that has high radon.

The result of a short-term screening test only indicates the potential for a radon problem. Short-term screening results of 4 pCi/L or above indicate that follow-up measurements are needed. Estimates of risk for you and your family are based on the result of these follow-up tests which are conducted in the living area (an area that is regularly occupied for two or more hours a day) of your home. Any decision to reduce radon levels should be based on the results of follow-up tests.

Fortunately, there are extremely effective means of keeping radon out of your home. Throughout the country, several million people have already tested for radon. Some houses tested as high as 2,000-3,000 pCi/L; yet, there hasn't been one house that could not mitigate to an acceptable level. Mitigation usually costs between $800-$2000.

Most often, the radon in your home's indoor air can come from two sources, the soil or your water supply. Compared to radon entering your home through water, radon entering your home through soil is usually a much larger risk. If you are concerned about radon and you have a private well, consider testing for radon in both air and water. By testing for radon in both air and water, the results could enable you to more completely assess the radon mitigation option(s) best suited to your situation. The devices and procedures for testing your home's water supply are different from those used for measuring radon in air. 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.

If you've tested your private well and have a radon in water problem, it can be easily fixed. Your home's water supply can be treated in one of two ways. Point-of-entry treatment for the whole house can effectively remove radon from the water before it enters your home's water distribution system. Point-of-entry treatment usually employs either granular activated carbon (GAC) filters or aeration systems. While GAC filters usually cost less than aeration systems, filters can collect radioactivity and may require a special method of disposal. Both GAC filters and aeration systems have advantages and disadvantages that should be discussed with your state radon office or a water treatment professional. Point-of-use treatment devices remove radon from your water at the tap, but only treat a small portion of the water you use, e.g., the water you drink. Point-of-use devices are not effective in reducing the risk from breathing radon released into the air from all water used in the home.