The U.S. Environmental Protection Agency (EPA) has named January as national Radon Action Month, in hopes of getting as many people as possible to test their homes for radon. The Radon is a naturally occurring radioactive gas produced by the breakdown of uranium, thorium, radium, and other radioactive elements that naturally occur in granites as well as some metamorphic and sedimentary rocks in soil, rock, and water and is widespread in the United States.
Radon is an odorless, clear radioactive gas that can cause
cancer. Most people only test their home at purchase, but the It is a good idea
to retest your home if you make any changes to the structure and every few
years to be sure radon levels remain low. In addition, if your home has a radon
mitigation system, it is important to monitor the system and retest at least
every two years to make sure the system is functioning.
According to the EPA about 21,000 people die each year from lung cancer caused by long term exposure to elevated levels of radon in their homes. Radon is the second leading cause of lung cancer in the general population, and is the leading cause of lung cancer in non-smokers. As radon gas is released from bedrock, it migrates upward through the soil and can seep into the basements of houses and other buildings through dirt floors, cracks in concrete, and floor drains. Radon has a tendency to accumulate in enclosed spaces such as buildings. 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 home acts like a vacuum, drawing radon in through foundation cracks and other openings.
Radon from soil is the main cause of radon problems in
homes, but sometimes radon enters the home through well water. You cannot
see, taste or smell radon. The only way to detect radon is to test. Short
term radon testing kits consist of a container of granular activated charcoal.
The charcoal absorbs the radon gas entering the canister from the surrounding
air. At the end of the radon gas test period, typically 3-7 days the canister
is sealed and sent to the laboratory in the pre-paid mailer for analysis. There
are also 90 day test kits.
Radon in air is ubiquitous- found in outdoor air and in the
indoor air of buildings of all kinds. The average indoor radon
concentration for America’s homes is about 1.3 pCi/L. It is upon this national
average indoor level that EPA based its estimate of 21,000 radon-related lung
cancers a year. The average concentration of radon in outdoor air is .4 pCi/L
or 1/10th of EPA's 4 pCi/L action level.
EPA recommends homes be fixed if the radon level is 4 pCi/L
(picocuries per liter) or more. However, there is no known safe level of
exposure to radon so, EPA also recommends that we consider fixing our home for
radon levels between 2 pCi/L and 4 pCi/L.
According to the EPA, radon levels in most homes can be
reduced to 2 pCi/L or below using standard mitigation techniques. Radon
mitigation takes one of two approaches either preventing the radon from
entering the home or reducing the radon levels by dilution after the radon has
entered the home. There are several techniques that can be used depending on
the type of foundation the home has. It is better to prevent radon from
entering the home in the first place so I will discuss the preferred methods of
prevention. The type of foundation, construction materials and condition will
determine the kind of radon reduction system that will work best. Homes are
built with some kind of foundation- a basement, slab-on-grade, a crawlspace, or
a combination of the three. It is common to have a basement under part of the
home and to have a slab-on-grade or crawlspace under the rest of the home. In
these situations a combination of radon reduction techniques may be needed to
reduce radon levels to below 4 pCi/L, which is the EPA regulated level.
However, be aware that there is a synergistic risk from active smoking and
radon exposure that increases the risk of getting lung cancer.
Soil suction techniques are the preferred method of mitigation and prevents radon from entering your home by drawing the radon from below the home and venting it through a pipe(s) to the air above the home or outside the house where it is diluted by the ambient air. An effective method to reduce radon levels homes with crawl spaces is covering the dirt floor of the crawl space with a high-density plastic sheet. A vent pipe and fan are then installed and used to draw the radon from under the sheet and vent it outdoors. This is called sub-membrane suction, and according to the EPA when properly installed is the most effective way to reduce radon levels home with crawlspaces.
In homes with concrete slab foundations or basements, sub-slab depressurization is the most reliable radon reduction method. One or more suction pipes are inserted through the floor slab into the crushed rock or soil underneath the home and a fan is used to draw the radon from under the slab or basement floor to a roof or wall vent. It is possible, and in many cases preferable, to install the suction pipe under the slab by running the pipe on the outside of the house. Another variation is to use the drain tiles or perforated pipe that are installed in modern homes to keep basements dry. Suction on these tiles or pipes can be effective in reducing radon levels. This system is most effective if the drain tiles are on the inside of the footer, sealed beneath the floor and form a complete loop around the foundation of the building. In homes that have sump pumps the sump can be capped so that it can continue to drain water and serve as the location for a radon suction pipe. There are kits that can be purchased for capping the sump pump. It is important that the sump cover lid is readily removable for service of the sump pump. Be aware that over time the perforated pipe can become clogged with silt.
There are several other techniques such as sealing cracks and passive methods that are often installed in new construction that are not as effective as active depressurization of the slab, basement or crawl space. As a temporary measure ventilation will reduce the radon levels by introducing more outside air, but it will increase your heating and cooling bills. After a mitigation system is installed do confirmation testing of radon levels before you make the last payment to the contractor to ensure that the mitigation system works. For more information of mitigation approaches and techniques see the EPA’s Consumer's Guide to Radon Reduction .