Radon is a common concern for homeowners and homebuyers throughout Montana. Our state's geology, soil conditions, and long heating seasons can contribute to elevated indoor radon concentrations. Fortunately, radon testing is straightforward, and elevated levels can typically be addressed with a professionally installed mitigation system.

Below are answers to some of the most common questions we receive about radon testing and mitigation in Montana homes.

1. Why should I test my Montana home for radon?

Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. It is colorless, odorless, and tasteless, meaning there is no way to detect it without specialized testing equipment.

Radon can enter a home through foundation cracks, construction joints, plumbing penetrations, and other openings in contact with the ground. Once inside, it can accumulate to concentrations that pose a long-term health risk.

According to the U.S. Environmental Protection Agency (EPA), radon is the second leading cause of lung cancer in the United States, after smoking, and the leading cause among nonsmokers.

Montana has a particularly high potential for elevated indoor radon concentrations. However, radon levels can vary significantly between neighboring homes, making individual testing essential.

The only way to know your home's radon concentration is to test it.

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2. My home doesn't have a basement. Do I still need a radon test?

Yes. Elevated radon concentrations have been found in Montana homes with basements, crawlspaces, and slab-on-grade foundations.

Although radon typically enters through areas in contact with the soil, no particular foundation type guarantees low radon levels. Even homes built on ventilated crawlspaces can experience elevated concentrations.

Every Montana home should be tested, regardless of its age, foundation type, or location.

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3. How much radon is too much?

Radon concentrations are measured in picocuries per liter of air (pCi/L).

The EPA recommends taking action to reduce indoor radon concentrations when the average test result is 4.0 pCi/L or higher. The EPA also recommends considering mitigation when concentrations fall between 2.0 and 4.0 pCi/L.

There is no known completely risk-free level of radon exposure. The risk of developing lung cancer generally increases with higher concentrations and longer periods of exposure.

For perspective:

• Below 2.0 pCi/L: Generally considered a relatively low concentration, although some risk remains.
• 2.0–3.9 pCi/L: Consider taking steps to reduce radon exposure.
• 4.0 pCi/L or higher: The EPA recommends corrective action.

A radon test provides a measurement of the home's indoor air during the testing period. Because concentrations can fluctuate with weather, seasonal conditions, and building operation, periodic retesting is important.

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4. Are radon levels higher in Montana during the winter?

Radon concentrations can be higher during Montana's colder months, although this is not always the case.

During the heating season, homes are typically kept closed, with less outdoor air entering through windows and doors. Temperature differences between indoor and outdoor air can also contribute to pressure conditions that draw soil gases into the building.

These factors may contribute to elevated indoor radon concentrations during the winter.

However, radon can be elevated at any time of year, and testing is appropriate regardless of the season.

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5. What happens if my home tests high for radon?

Elevated radon concentrations are common and, fortunately, are usually manageable.

The most common corrective measure is an active soil depressurization system. These systems use a continuously operating fan and piping to draw radon-containing soil gases from beneath the foundation and discharge them safely above the building.

A properly designed and installed system can substantially reduce indoor radon concentrations, often bringing them below the EPA's recommended action level.

We recommend working with a qualified radon mitigation contractor, preferably one certified through the National Radon Proficiency Program (NRPP) or National Radon Safety Board (NRSB).

A follow-up radon test should always be performed after installation to verify that the system is effectively reducing indoor concentrations.

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6. I'm buying a home in Montana. Should I have it tested for radon?

Absolutely. Radon testing is a worthwhile part of the home inspection process, whether you're purchasing an older home or new construction.

Because radon cannot be detected through a visual inspection, a specialized test is necessary to determine the indoor concentration.

If elevated concentrations are identified, buyers and sellers can negotiate how to address the condition as part of the real estate transaction.

Possible arrangements include having the seller install a mitigation system before closing, negotiating a credit toward installation, or having the buyer arrange for mitigation after purchasing the property.

The important thing is to understand the home's radon concentration before completing the purchase so you can make an informed decision.

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7. If the seller agrees to install a mitigation system, how can I ensure the work is done properly?

If radon mitigation is included in your real estate negotiations, we recommend establishing clear expectations for the installation.

Ideally, the agreement should specify that:

• The contractor holds a recognized professional radon mitigation certification, such as NRPP or NRSB.
• The system is installed in accordance with applicable ANSI/AARST radon mitigation standards.
• A post-installation radon test is performed to verify its effectiveness.
• The buyer receives documentation of the installation, operating instructions, and any applicable warranties.

A qualified contractor should also explain how to monitor the system and recognize potential equipment failures.

Working with your real estate agent to establish these expectations can help avoid misunderstandings and ensure the system provides effective, long-term protection.

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8. I'm buying a newly constructed home with a radon system. Do I still need to test?

Yes. The presence of a radon system does not guarantee that indoor radon concentrations are acceptable.

Some newly constructed Montana homes include passive radon-resistant construction features, such as sub-slab piping that extends through the building and terminates above the roof.

These systems are intended to provide a pathway for soil gases to escape without the assistance of a mechanical fan. If testing reveals elevated radon concentrations, a fan may be added to convert the passive system into an active mitigation system.

Other homes may already have an active system installed.

Regardless of the configuration, testing is the only way to verify the home's actual radon concentration.

We recommend testing new construction during the inspection period, even when radon-resistant construction features are present.

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9. I'm building a custom home in Montana. Should I test the soil before purchasing the lot?

Soil radon testing is generally not a reliable way to predict the radon concentration that will eventually be present inside a completed home.

Indoor radon levels depend on several variables, including foundation construction, soil permeability, ventilation, and pressure differences between the building and surrounding soil.

Instead of relying on preconstruction soil testing, we recommend incorporating radon-resistant construction features into the home's original design.

These measures may include a gas-permeable layer beneath the slab, a soil-gas collection system, properly sealed foundation penetrations, and vent piping designed for future activation.

Incorporating these features during construction is generally easier and less expensive than retrofitting an existing home.

Once the home is complete, a radon test should be performed to determine whether additional mitigation is necessary.

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10. A radon contractor suggested a phased approach to mitigation. Is that a good idea?

It depends on the circumstances.

Some Montana homes, particularly those with multiple foundation types, additions, or complicated sub-slab conditions, may require a more involved mitigation design.

In certain situations, a contractor may recommend installing an initial system, measuring its performance, and making modifications if necessary.

This can be a reasonable approach when the contractor clearly explains the proposed work, anticipated costs, and conditions that might require additional measures.

However, homeowners should be cautious of proposals that do not clearly define the scope of work or potential additional expenses.

We recommend requesting a written proposal outlining the intended approach, performance expectations, and any follow-up testing.

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11. How long does a radon mitigation system last?

A properly installed and maintained radon mitigation system can remain effective for many years.

The piping and other permanent components typically have long service lives. However, active mitigation systems rely on an electric fan that operates continuously and may eventually require replacement.

Many radon mitigation fans carry a manufacturer's warranty of approximately five years, although their actual service life may be considerably longer.

Homeowners should periodically check the system's pressure indicator, commonly called a manometer, to verify that the fan is maintaining suction. A normal manometer reading does not, however, confirm that indoor radon concentrations remain low.

The EPA recommends retesting the home at least every two years after mitigation, as well as after significant renovations or changes that could affect the system's performance.

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12. How often should I test my Montana home for radon?

Even if your home has previously tested below the EPA's action level, radon concentrations can change over time.

Changes in foundation conditions, ventilation, HVAC equipment, and building operation can influence the amount of radon entering and accumulating inside a home.

As a practical recommendation, consider retesting approximately every two years, particularly if your home has an active mitigation system. Testing is also recommended after major renovations or changes to the building.

For homeowners who have never tested, the best time to start is now.

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Radon Testing With Inspect Montana

At Inspect Montana, we believe homeowners and homebuyers deserve clear, reliable information about the buildings they own or are considering purchasing.

Radon testing is a simple way to better understand your home's indoor environment and identify a potential health concern that would otherwise go unnoticed.

Whether you're purchasing a home, building new, or have lived in your Montana home for decades, radon testing can help you make informed decisions about your property and your family's long-term health.

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