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Friday, November 20, 2009

Facts About Radon Testing

Usually radon tests are performed on an "as requested" basis by a buyer. Over the years there has been an increased concern of radon levels in the home. Radon testing has become commonplace in the home buying process. However there are often many questions surrounding radon screening tests. The following information is intended to help answer some of the common questions and to address confusion that is frequently expressed.

What is Radon gas?

Radon is a radioactive gas. It is the result of a natural breakdown of uranium in the ground, including soil, rock and even water. This gas seeps into a house because most homes periodically have negative air pressure. In other words, they are sucking in air.

Testing for radon is not a test to determine whether there is or is not radon in the house, but instead it is a test to determine how much radon exists. It is also important to understand that any home is susceptible to a radon problem. This includes homes with or without basements, old homes, new homes, etc. The EPA (Environmental Protection Agency) has indicated that when a person breathes air containing higher concentrations of radon, they have an increased risk of acquiring lung cancer.

At the present time the EPA has recommended efforts to reduce radon levels in a home if testing indicates that the levels are currently at or above 4.0 pico Curies per liter. Some questions have been raised recently about whether the EPA intends to lower the "accepted level", but at the present time 4.0 pico Curies per liter remains the threshold level.

The EPA has also indicated that radon testing should be performed under "closed house" conditions. Specifically, all windows and exterior doors must be closed at least twelve hours prior to the start of the test, and also for the duration of the test. Testing lasts a minimum of forty-eight hours. Normal "in and out" traffic is allowed during that time, but the doors and windows must not be left open. Once again, it is important to understand that EPA establishes these rules in order to ensure accurate testing. All windows must be kept closed during the test, not just those windows in the immediate vicinity of the testing device. This is basically done to simulate how the house normally is (on average) throughout the year.

In regards to the use of air conditioners we would offer that central air conditioning systems can be used during radon testing since they do not allow for the free exchange of air between the exterior and the interior. Some window and wall mounted air conditioning units do not assure conformance with closed house conditions and, as a result, in many cases window-mounted air conditioners should not be used during radon testing.

Where is the test done?

According to the EPA, radon testing should be performed in the lowest livable level of the home. In most cases this means that the basement becomes the test site, assuming that it is a full depth basement. Whether the basement is currently finished living space or not, it is considered a livable level even if the basement does not have an abundance of headroom. Crawl spaces would not meet these criteria. In many old farm houses basements are of minimal depth and, as a result, could not be used as workshop space or "livable space". In these instances the first floor would then be tested.

The radon testing device should be placed in a somewhat central location of the lowest livable level. It should be placed an appreciable distance above the floor (typically at least 20 inches). It should not be placed directly adjacent to an exterior wall, near windows, near venting appliances (furnaces, water heaters, clothes dryers, etc.), in a closet, or next to a drainage crock or sump.

There are various testing devices that can be utilized for radon screening. Charcoal canisters are the simplest type of testing device. They are accurate, but they have their limitations and can be prone to false-positive readings in some situations. They are clearly not tamper-resistant. Most reputable radon testing firms utilize electronic monitors. These monitors take air samples continuously throughout the duration of the test period, measuring the levels of radon in the air during the test. The levels of radon will vary throughout the test, and the final result is the average level during the test. The highly accurate monitors that are utilized by our office also monitor temperature, relative humidity and barometric pressure. In addition, the monitors have a tilt-detecting mechanism. This provides some tamper-resistance.

It is important to understand that the radon levels in a home vary over time. In fact, the levels vary from hour to hour, let alone day to day, week to week or month to month. As a result, the screening tests that are performed are essentially a forty-eight hour "snapshot". A similar test performed at a different time in the same house will usually render a slightly different result, although it would probably be a result in the same range as the first result. There have been times when we have performed tests that have resulted in radon levels just above the 4.0 piCu/l threshold. Sometimes, buyers or sellers will opt for a second test. The second test result might be higher or lower than the first result. This is not because one test is more accurate than the other, but instead because the tests were performed at a different time. One logical approach would be to average the two test results to determine the average level of exposure in the house over the two 48 hour snapshots.

What do you do if your radon level is over 4.0-

Active radon mitigation systems are routinely installed when testing shows radon levels above 4.0 pico Curies per liter. These systems are relatively easy to install, and the cost of operation is minimal. Essentially, most radon mitigation systems provide a means to suck air from beneath the basement or slab floor and exhaust it to the exterior through the use of a simple PVC pipe and an in-line fan.

Radon levels are quite unpredictable, and it is not possible to predict with any appreciable accuracy what the levels of radon might be in one home versus another. One house on a street may have a level of radon higher than 4.0 and the house across the street or next door may have a reading below 4.0.

For more information visit this website:

Any individual or firm performing radon tests must do so in concert with an approved and licensed laboratory and all testing devices must be calibrated and approved for use. You should specifically ask anyone under consideration for radon testing whether their testing equipment and protocol meets these criteria.

This is an example of what a testing device looks like. You can also buy home kits.


  1. Thanks for Good Articles. I wonder if Radon Mitigation Fan can help?

  2. Maybe most if not all home inspectors are already offering radon testing as part of their services. In Minnesota where my brother bought his first house two years ago, radon testing was included on the contract thanks to their reliable home inspections (St. Paul, MN) company which made my brother aware about its importance.

    So Steve, how do home inspectors go in Rochester as far as radon mitigation is concerned?