Radon is a colorless, odorless radioactive gas that seeps up from the earth. When inhaled, it gives off radioactive particles that can damage the cells that line the lung.

Long-term exposure to radon can lead to lung cancer. In fact, over 21,000 lung cancer deaths in the US each year are from radon, making it a serious health concern for all Minnesotans.


Where does radon gas come from?

Radon is produced from the natural decay of uranium that is found in nearly all soils. Uranium breaks down to radium. As radium disintegrates it turns into a radon, a radioactive gas. As a gas, radon moves up through the soil and into the air you breathe.

How dangerous is radon?

Radon is the number one cause of lung cancer in non-smokers and the second leading cause of lung cancer (after tobacco) in smokers. Thankfully, this risk should be entirely preventable through awareness and testing.

Where is your greatest exposure to radon?

While radon is present everywhere. There is no known, safe level, and your greatest exposure is where it can concentrate: indoors where you spend most of your time – at home. Your home can have radon whether it be old or new, well-sealed or drafty, and with or without a basement.

How serious a problem is radon in Minnesota?

High radon levels exist in every state in the U.S. In Minnesota, one in three homes has radon levels that pose a significant health risk, and nearly 80& of counties are rated High Radon zones.

Some factors that further contribute to Minnesota’s high radon levels include:

  • Minnesota’s geology produces an ongoing supply of radon
  • Minnesota’s climate affects how our homes are built and operate
How does radon enter a home?

Since radon is produced from soil, it is present nearly everywhere. Because soil is porous, radon gas is able to move up through the dirt and rocks and into the air we breathe. If allowed to accumulate, radon becomes a health concern.

Two components that affect how much radon will accumulate in a home are pathways and air pressure. These components will differ from home to home.

  • Pathways are routes the gas uses to enter your home and found anywhere there is an opening between the home and the soil.
  • Air Pressure between your home’s interior and the exterior soil is what helps to draw radon gas into the home via the pathways.

Radon can enter your home through cracks in concrete slabs, spaces behind brick veneer walls that rest on uncapped hollow-block foundations, pores and cracks in concrete blocks, floor-wall joints, exposed soil, as in a sump or crawl space, weeping tile (drain, if drained to an open sump), mortar joints, loose fitting pipe penetrations, open tops of block walls, open tops of block walls, building materials such as brick, concrete and rock, and well water (though not a common source in Minnesota homes.


Minnesota homes commonly operate under a negative air pressure, especially during the heating season. This means that the air pressure inside your home is typically lower than the surrounding air and soil, creating a vacuum that pulls soil gases, such as radon, into the home via pathways. Even if the ground around the house is frozen or soaked by rain, the gravel and disturbed ground underneath the house remains warm and permeable, attracting radon gas from the surrounding soil.

Other factors also contribute to air pressure changes in a home, including:

  • Stack Effect: As warm air rises to the upper portions of a home, it is displaced by cooler, denser outside air. Some of that displaced air comes from the soil.
  • Down Wind Draft Effect: Strong winds can create a vacuum as they blow over the top of the home.
  • Vacuum Effect: Combustion appliances like furnaces, hot water heaters and fireplaces, as well as exhaust fans and vents, can remove a considerable amount of air from a home. When air is exhausted, outside air enters the home to replace it. Some of this replacement air comes from the underlying soil.

In general, whenever air enters a home from the underlying soil, some radon will likely come with it.

What happens AFTER radon gets into the home?

Radon levels are often highest at the entry point – typically in the lower part of a building. As radon gas moves upward, diffusion, natural air movements and mechanical equipment (such as a forced-air ventilation system) distribute the radon through the home. Radon gas becomes more diluted in the upper levels of the home because there is more fresh air for it to mix with.

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

Understanding how radon moves through the home environment helps to explain why timing and location are important factors to consider when conducting a radon test.

Technicians testing for radon in a commercial building



A radon test is the only way to find out how much radon is in your home and if you and your family are at risk. Performing a radon test on your own is easy, inexpensive and takes only a few minutes of your time. The results of a properly performed radon test will help you determine if you need to take further action to protect yourself from the health risks of radon.

What type of radon test kit should I use?

There are two basic types of radon tests available to the public: short-term and long-term tests.

Short-term tests measure radon levels for 2-7 days, or use a continuous monitor for a minimum of 48 hours, depending on the device. While short-term tests do not measure the annual average level of radon, they do offer a quick and inexpensive way to “screen” for radon in a home.

Long-term tests determine the average concentration for a minimum of 90 days. Long-term tests are the best way to estimate the average amount of radon in the home during the year, particularly if a year-long test is done to include both heating and cooling seasons.


It’s important to follow the instructions that come with the radon test kit. Before performing a test, keep these guidelines in mind:

  • Time of year to test: The amount of radon in homes is usually highest during the heating season. Long-term tests should span the heating and non-heating season.
  • Weather patterns: Weather patterns can influence how radon gets into your home. Short-term tests should not be conducted during severe weather or unusually high winds.
  • Test location: Test the lowest level of the home that is regularly used. For example, if you spend more than 8-10 hours a week in the basement, testing the basement is highly recommended.
  • Disturbances: Place the kit at least 20 inches above the floor in a location where it won’t be disturbed – away from drafts, high heat, high humidity and exterior walls. Test kits that are disturbed or moved during a test may provide inaccurate results.
  • Timeliness of analysis: Once you’ve finished, reseal the package and send it to the lab specified on the package. Radon test results may not be accurate if the test kits are not sent to the laboratory as soon as possible after completing the test.
How often should I test for radon?
  • It is highly recommended that every Minnesota home be tested for radon – even those built radon-resistant.
  • You should retest your home every 2-5 years and save your results.
  • Be sure to test before and after you make any major structural renovations such as building an addition or finishing a basement. Radon-resistant techniques can be inexpensively included as part of the renovation, if needed. You should also perform a radon test after buying a new heating system or adding central air conditioning.


Radon testing units, along with the beginnings of a radon mitigation system

What are the units of radon measurement?

Picocuries per liter (pCi/L) is a unit that measures levels of radon/radioactive gas.

What is the recommended action based on my results?

The EPA & MDH set the recommended action level for radon at 4.0 pCi/L:

  • Above 4 pCi/L = Fix your house (mitigation)
  • 2 pCi/L to 4 pCi/L = Consider fixing your house

To apply the recommended action level correctly, the results should be based on the annual average level of radon measured in a home. If the annual average level of radon is above 4 pCi/L, EPA & MDH recommend that steps be taken to lower it. While it isn’t possible to reduce radon to zero, the best approach is the lower the radon level as much as possible. Any amount of radon, even at or below the recommended action level, carries some risks.


Are radon levels regulated?

In Minnesota, radon levels are not regulated. It is up to the homeowner or home buyer to decide what amount of radon is an acceptable risk for your family.

How much radon is safe?

There is no safe level of radon. Your risk for lung cancer increases with higher levels of radon gas and increased exposure.


Radon mitigation is any process or system used to reduce radon concentrations in the breathing zones of occupied buildings. The goal of a radon mitigation system is to reduce the indoor radon levels to below the EPA action level of 4 pCi/L. A quality radon reduction (mitigation) system is often able to reduce the annual average radon level to below 2 pCi/L.

There are several methods used to mitigate or reduce radon levels in your home. Some methods prevent the entry of radon, while others reduce radon levels after it enters the home.


Houses are generally categorized by their foundation design, basement, slab-on-grade or crawl space. The foundation determines the radon reduction system that will work best to prevent gases from entering your home. Types of radon mitigation systems include Ventilation, Suction, & Passive.


Lowering high radon levels requires technical knowledge and special skills. The right system will depend on a number of factors, including the design of your home. An experienced radon mitigation professional is your best resource to assess and advise you of your options. SRC can help you determine the best course of action as well as mitigate your home for you.

*Excerpted from the Minnesota Department of Health Indoor Air Unit Radon Brochure

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