Minnesota Radon

Radon in Minnesota and Minneapolis / Saint Paul Suburbs

Radon is a radioactive gas which is present in 1/3

of all Minnesota homes according to the MDH (Minnesota Department of Health). Because Radon is a gas, it is able to move through spaces in the soil or fill material around a home's foundation. Minnesota homes tend to operate under a negative pressure - this is especially true in the lowest portions of the home and during the heating season. This negative pressure acts as a vacuum (suction) that pulls soil gases, including radon, into the lower level of the structure. Some causes of home vacuum are:

Heated air rising inside the home (stack effect).
Wind blowing past a home (downwind draft effect).
Air used by fireplaces, wood stoves, and furnaces (vacuum effect).
Air vented to the outside by clothes dryers and exhaust fans in bathrooms, kitchens, or attics (vacuum effect).

Due to the vacuum created by the negative pressures, the diagram to the left shows how Radon enters the home. The most common area is the basement of the home through cracks and gaps in the floor or walls. A Radon test performed by 7 County Home Inspection uses an EPA approved method for measuring these gases in the lowest level of the home, typically where the highest concentration of gas would exist.

What happens after radon gets into the home?

Once radon enters a home it moves freely throughout the indoor air and people can breath it into their lungs where it can cause cell damage that may lead to lung cancer. Understanding how it distributes through the home environment can help explain why timing and location are important factors to consider when conducting a radon test.

The level of radon is often highest in the lower part of the building. Radon moves through a house by diffusion and natural air movements and it can be distributed by mechanical equipment such as a forced-air ventilation system. As radon moves away from the home's foundation or other entry points, it mixes (and is diluted) into a greater volume of air. In addition, more dilution often occurs in the upper levels of the home because there is more fresh air ventilation there.

Greater dilution and less house vacuum may also occur when the house is more open to the outdoors during the non-heating season. This generally results in lower indoor radon levels in the summer compared to the winter.

How can I find out if my home has a radon problem?

A radon test is the only way to find out how much radon is in your home. Performing a radon test on your own is easy, inexpensive, and can be done privately. Every home is unique due to its local soil, construction details, maintenance and degree of depressurization. Therefore, test results from nearby homes cannot be relied upon to predict the radon level in another home. Likewise, previous test results may not reflect the current and future radon levels for a home that has been remodeled, weatherized or had changes so its heating air conditioning or other ventilation systems such as exhaust fans.

The MDH recommends that all Minnesota homeowners test their homes for radon. The results of a properly performed radon test will help homeowners determine for themselves if they need to take further action to protect their family from the health risks of radon in the home.

Contact the MDH Indoor Air Unit for more information on where to obtain low cost radon test kits, the types of test kits, how to perform tests properly and how to interpret the test results.

How can I protect my family from radon?

A number of steps can be taken to lower the amount of radon in a home. A quality radon reduction (mitigation) system is often able to reduce the annual average radon level to below 2 picoCuries per liter (see Minnesota Radon Testing and Use of Test Results for discussion of radon levels and health risks). Experienced radon mitigation professionals can install appropriate control systems. Contact MDH for information regarding radon mitigation.