Written by Randy Howland

This information will help you decide if a Radon test is something that is necessary for the home you may be purchasing. If the information raises any questions please don’t hesitate to contact us.

The concerns
about Radon
Radon in homes causes more deaths annually than fires, drownings, and airplane crashes combined.  The U. S. Department of Health attributes it to an estimated 19-20,000 deaths annually.  It is the second largest cause of lung cancer (approximately 12.5% of all lung cancer) after cigarette smoking.  With people spending on average 70% of their time at home a measurement of 4.0 pCi/L, the suggested federal action point for Radon in a house, would be the equal to smoking 10 cigarettes per day. Put another way, at this action level you increase the  risk of lung cancer by 50%.

The reason why our government and scientists are so concerned about Radon is because it originates from Uranium-238, and it is radioactive. It is the natural decay of Uranium in the rock, soil, and water in the Earths crust that leads to Radon. Naturally existing low levels of uranium occur widely in the Earth’s crust.  Wherever you find Uranium you’ll find Radium and the gas that emanates from it called Radon. Radon is a Noble gas (Noble means that it avoids interacting with other common elements). Radon being a noble gas also means that it is tasteless, odorless, colorless, and non-flammable. Radon is also eight times heavier than the air we breathe.

Radon decays into other isotopes called Radon daughters such as Polonium and Lead which attach themselves to dust particles in the air and when inhaled attach themselves to our air passageways. In our lungs and respiratory tract, they continue to decay and emit radiation. This radiation leads to mutations in the lung tissue and can cause cancer.

Uranium and the other radioactive elements that Uranium transforms into will always be with us. The breakdown and release of its radiation is called its HALF-LIFE. This means that if you have one pound of an element and its half-life is one year, at the end of one year you would now have ½ pound of that element. After two years ¼ pound, 3 years 1/8 of a pound.  It will always be getting smaller but will never totally disappear. The half-life of Radon is 3.8 days.

Where Radon is found and what it is found
Radon is found in all 50 states, and begins in a few common places where Uranium can be found.  Uranium is obviously in Uranium itself, but it can also be found in Shale, Phosphate, and that which is most applicable to us in the Northeast is Granite Bedrock. Because we have known deposits of granite we are at the highest potential risk for Radon.


Zone 1 Counties having a predicted average indoor radon screening level greater than 4 pCi/L (red zones)   Highest Potential  

Zone 2 Counties having a predicted average indoor radon screening level between 2 and 4 pCi/L (orange zones)   Moderate Potential  

Zone 3 Counties having a predicted average indoor radon screening level less than 2 pCi/L (yellow zones)   Low Potential  

The shoreline of Connecticut, --Fairfield, New Haven, Middlesex, and New London counties are considered by the U.S. Environmental Protection Agency to have the potential for the greatest risk of exposure to Radon. Radon is measured in Pico Curies per Liter, and we have a greater possibility of counts exceeding the minimum government action point of 4.0 Pico Curies per liter. A Pico Curie/Liter is a measure of the rate of radioactive decay of Radon. At 4.0 Pico Curies/Liter there will be approximately 12,672 radioactive disintegrations in one liter of air during a 24 hour period.

How Radon gets into a houses

The major sources of Radon in indoor air are:

  1. The gas that travels through the ground soils

  2. The off gassing from ground water and well drinking water

  3. Building materials

  4. Outdoor air

Gases passing through the soil represent the predominant source. As Radium decays and forms Radon gas, the gas fills the air space between the grains of soil and moves in all directions, rising slowly upward.

Different environmental factors will help determine how much radon gets to the surface. A difference in temperatures between the air and ground causes a pull as warm air rises, creating a vacuum that draws the Radon from the ground. The same effect takes place on windy days, when air passing over the ground creates suction in the top layer of the soil.

The difference in the permeability of the soil can also determine Radon’s path. Sandy soils with large numbers of air pores are a good pathway for the gas, versus clay like soils that are highly compacted. Weather also affects how much Radon can get through the soils. When it rains, moisture fills the soil pores and cuts the movement of the gas by two-thirds. The same thing happens when the ground freezes.

It is this vacuum effect that draws Radon into our homes. We heat our homes and we all know that hot air rises. This combined with the fact that air pressure in our houses is lower than in the outdoors makes our homes the best path for Radon to travel through. Researchers say the amount of Radon in most homes is ten times higher than outdoors. As the hot air in our houses rise it creates a lower pressure in our basements and lowest living level. This lower pressure sucks the Radon into the house, much like using a straw in a glass of soda. The Radon gas enters through:

  • Cracks in floors and walls

  • Openings such as sump pumps and drains

  • Crawl spaces with unfinished dirt floors

  • Construction joints

  • Radon also enters through our drinking water when our water is supplied by a well.

Radon can also attach itself to ground water as it passes through soils and granite rock. We then pump this water through wells and into our houses where it is released into the air when we take showers, drink water from the tap, and even when we flush the toilet.  Most wells in the New England states, that have large outcroppings of granite, have elevated concentrations of Radon in their well water.

The risks
There are two methods in which these radiation levels are measured. I have mentioned Pico curies per liter which refers to the levels of Radon gas in the house; another type of measurement that should be mentioned is WORKING LEVEL which is the alpha radiation or energy release from radon’s daughter products. You will most often here Radon results being presented in Pico curies but working levels are also used.

What is an acceptable level?  The government realizes that exposure to almost any level of Radon presents a health risk. As I mentioned previously the E.P.A.s recommended action level is 4.0 Pico curies per liter. It is at this point that it is suggested that the home be remediated. This level was arrived at after lung cancer studies of uranium miners exposed at a level of 400 Pico curies per liter. Many relocation companies insist that the house test level be below 4.0 pCi/l.

At the 4.0 Pico curies per liter level a cigarette smoker has an eight times greater risk than a non smoker of coming down with lung cancer.  At the 4.0 level a person receives in their home during the course of 12 years the same radiation exposure as if they worked for 5 years in a uranium mine, and you increase your chance of incurring lung cancer by about 50%. 2 ½ %  out of  every 100 persons with radon at this level in their homes can develop lung cancer. At 20 Pico curies/liter it is equal to a person who is two pack a day smoker.

Reference: EPA's Guide to Radon Public Heath Risk for Smokers and Non-Smokers

How Radon levels are determined
Radon levels can be determined in both short term, 2 to 90 day tests, and long term tests. 48 hours was decided upon as the minimum acceptable level because it is known that radon levels fluctuate with the time of day. It was also felt that unforeseen circumstances may alter results if only a 24 hour test period were used, so 48 hours was chosen as the shortest minimum measurement period. When radon is a concern for my clients and time is not of the essence I recommend that the longer we can test, the more accurate our results will be. With this in mind it is believed that up to 30% of the radon tests in real estate transactions are subject to something that may bias the results.

In the real estate transaction marketplace, remembering that we are dealing with short term tests of between 2 and 7 days, the three most common testing methods are, 1) Activated Charcoal Devices, 2) Continuous Radon Monitors, and 3) Electret Ion Chambers. The charcoal and electret tests are called passive tests in that they do not need power to function. These types of tests are exposed to the air in the home and then sent to a laboratory for analysis. The continuous radon monitors work by continuously measuring and recording the amount of radon or its decay products in the air. They require power to function and record their information.

The electret canisters have been determined by the federal government to be the most reliable of the three testing methods. The disparity in the reliability of charcoal canisters and radon monitors is in the number of manufacturers producing these devices and that the reliability of the results can vary dramatically between manufacturers.

Inquiring-Eye Home Inspectors find the E-Perm or electret method preferable. These devices have an electro statically charged Teflon disk which is actually the electret itself. When opened, radon in the room (if present) diffuses into the chamber and begins to decay. When this occurs, ions are generated and collected on the charged electret which decreases the electrostatic voltage. The changes in the charge are then made and the radon count can be determined.

The following conditions should exist for twelve hours prior-to and during the test period:

  1. Windows and external doors should remain closed, except for normal entry and exit.

  2. Non-essential ventilation devices should not be operated.

  3. Dehumidifiers should be turned off.

The testing devices are placed in the lowest living level where routine occupancy may occur. This may include finished basements, basements that are used for laundry, workshop, and playroom purposes. OR  for clients who are purchasing,  basements where an expressed  future active intent may be indicated. With a passive device the canisters should be left for a minimum test period of 48 hours.  

Radon in Air Test Device Placement (Protocols)

  Closed building conditions (Government protocol document number 2.3.2)

  1. Short term tests (2-7 days) for Real Estate transactions should be made under closed house conditions; which are windows on all levels and external doors should be kept closed (except for normal entry and exit) during the measurement period.

  2. Tests lasting less than four days should meet closed house conditions 12 hours prior to the placement of the test devices.

  3. If the above conditions are met, the test devices shall be placed for a minimum of 48 hours (two days).

  4. If closed house conditions are not met, (windows not closed), 12 hours prior to the placement of the test devices, the house will be closed at the time of placement, and the test devices shall be left for a minimum of 96 hours (Four days).

  Measurement Location (Government protocol document number 2.2)

  1. Test devices should be placed in the lowest part of the home suitable for occupancy or where residents may spend time. Examples: unfinished basement laundry, unfinished basement work or play areas, unfinished basement storage areas (but normally accessed areas). In Real Estate transactions, it may be where ever the client determines.

  2. The measurement should be at least 12 inches from the exterior foundation, in no case, closer than 3 feet to windows, doors or other potential openings in the exterior wall.

  3. The measurement should be at least 20 inches from the floor, 4 inches from other objects, and 12 inches from the ceiling.

  4. Test devices should be placed far enough away from heat sources, fans, or air conditioners.

How a Radon problem is solved
Once a test has determined that a radon problem exists a course of action to relieve the problem must be decided upon. This is called a radon mitigation system. This is any system or steps that are designed to reduce radon concentrations in the indoor air of a building. There are several methods that can be used.  Some techniques prevent radon from entering the home while others reduce radon levels after it has entered.  

As simple as it sounds, sealing your basement or slab from radon in the soil is the first method. This can be a formidable task and one that will most likely not work effectively. The example that I like is thinking of your basement as the hull of a boat, can you guarantee that you can find all the hundreds of possible cracks in it so that your house would not sink? This step also involves sealing crawl spaces, sump pumps and all wall penetrations.

The method considered the most effective is sub-slab depressurization, or active soil depressurization which removes the radon from the ground below the slab or basement before it enters the house. A system of pipes is placed below the slab floor and an electric exhaust fan is used to draw the radon into the pipes and remove it to the outdoors.
Passive methods of this concept exist where no electric exhaust fan is used.

Other reduction systems used are:

  1. Changing the atmospheric pressure in the lowest living level by the use of fans. These fans increase the pressure in the lowest living level and thus force the radon to seek an easier path. and

  2. Heat recovery ventilators that increase the ventilation with the outdoors. These units are placed in the lowest living level and exchange air with the outside air, thereby reducing radon levels.

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As previously mentioned, an additional source of radon in air can be a private well water system. The well water we drink filters through many layers of bedrock and soil below our homes into an aquifer which passes this water through to our well. If the water particle, as it is passing through the soil, comes in contact with bedrock containing decaying uranium the radon gas particle associated with the decaying uranium can attaché itself to the passing water particle. The two travel through the soils together. The radon particle becomes a portion of the water particle. The two are then drawn from the ground by our well to enter our homes as drinking water. The radon would rather be in air though, so when the water enters the atmosphere in our homes the radon disconnects itself from the water particle. When you run a tub or sink faucet, flush a toilet, or take a shower, the radon particle enters into the atmosphere and the air we breathe. This radon in water becomes a portion of the radon in air that may already be existing in the home.

Unlike radon in air the federal government has not determined a maximum acceptable level for radon in water. When we measure radon in air it is capturing a representative sample of the air that is present at the time of the test. With radon in water it is a measurement of what is contained in the water. The radon present in the water will contribute to the radon in air that is present. But how much it contributes can be directly affected by how much water is run. This is a direct relationship with the number of occupants in the house, and the volume of air, or the cubic footage of the house. Since each house is different in both of these aspects it its difficult to say there is a direct correlation of radon in water and what it will add to the radon in air.

As a rule of thumb, you can figure on a 10,000 to 1 water to air ratio, which means that for approximately every 10,000 pCi/L of radon that is in the water, it will "off-gas" approximately 1pCi/L into the air. This amount can vary depending on how much water is run and the volume of air present.

With the lack of federal action, the State of Connecticut has set an action point for radon in water entry. It is 5000 pCi/l in water or more. At this point or above it is suggested that the radon entering the house be treated. Radon in water can be effectively reduced by one of two methods. Aeration treatment or granular activated charcoal. In both of these treatment methods it is important to treat the water where it enters the home. Trying to treat the water at the kitchen sink, for instance, would not be effective. Aeration can either be spraying the water to dislodge the radon particle, or mixing the water with air that agitates or bubbles the water.

Granular activated charcoal systems filter the water through a charcoal bed. The radon is retained in the charcoal. Charcoal systems do require replacement of the now "radioactive" charcoal. If not regularly maintained or for some reason water consumption increases in the house this type of system may allow increasing amounts of radon to enter the home. Aeration systems cost approximately $3500.00. Charcoal systems $1000 to 1500.00.

Additional Information about Radon in Water provided by the Connecticut State Department of Health

Radon gas can also enter homes through the water supply.  Radon dissolves and builds up in water from underground sources, such as wells. The radon in your water can enter the air in your home when you use water for household activities such as showering, washing clothes and cooking.

For every 10,000 picocuries per liter (pCi/L) of radon in your water, 1 pCi/L is added to your radon in the air. If your water comes from a lake, river, or reservoir (surface water), radon is not a concern. The radon is released into the air before it reaches your home. 

Some radon stays in the water. Radon in the water you drink can also contribute to a very small increase in your risk of stomach cancer. However this risk is almost insignificant compared to your risk of lung cancer from radon.



For collection and analysis of radon in water, you should use the services of a qualified radon measurement professional and a DPH approved laboratory

The Radon Program also maintains a List of Radon Mitigation Professionals.  Mitigation contractors in CT must also be registered as 'Home Improvement Contractors' with the Department of Consumer Protection.

Use the links below to find out more about radon in water:

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