How Long Should a Radon Test Be?

Radon testing duration depends on the type of test you are doing.

A short-term radon test is measured in days. A long-term radon test is measured in months.

In Canada, a short-term radon test is generally at least 48 hours, while a long-term radon test should run for at least 91 days, or about 3 months. Testing duration matters because radon levels can change over time. A test that is too short, moved too often, or placed incorrectly may not give you useful information about your home’s typical radon level.

For Canadian homeowners, including Manitoba and Winnipeg homeowners, the key is to choose the right test for your situation and follow the instructions carefully.

How Long Is a Short-Term Radon Test?

A short-term radon test should run for at least 48 hours.

C-NRPP defines a short-term radon test as a radon test that lasts at least 48 hours but less than 3 months. Short-term testing can be useful when you need faster information or want a quick screening result.

For example, a homeowner might use a short-term test after a mitigation system is installed, or as a first look before deciding what to do next.

The important thing to remember is that short-term radon testing gives a snapshot. It measures radon levels during that specific testing period. Because radon levels can rise and fall, a short-term test may not represent your home’s long-term average radon exposure.

That does not make short-term testing useless. It simply means the result should be understood for what it is: a shorter measurement over a limited window of time.

How Long Is a Long-Term Radon Test?

A long-term radon test should run for at least 91 days, or about 3 months.

Health Canada says it is important to conduct a long-term radon test for a minimum of 3 months. Health Canada’s residential measurement guide also notes that Health Canada does not recommend testing for periods shorter than 91 days when assessing a home’s radon level.

Long-term testing gives a better picture of a home’s average radon level. This matters because radon is not always the same every day. A longer test helps smooth out short-term changes and gives homeowners more useful information for making decisions.

If you are testing your home to understand long-term indoor air quality or whether mitigation may be needed, long-term testing is usually the better option.

Why Does Health Canada Recommend Long-Term Testing?

Health Canada recommends long-term testing because radon levels can change.

Indoor radon levels may be affected by weather, season, ventilation, heating, air pressure, and how the home is used. For example, opening windows, changing airflow, or testing during a very specific weather pattern can affect the result.

In Manitoba, winter can also matter because homes are often closed up and heated for long periods. When a house is sealed tightly, indoor air movement can affect how soil gas enters through the foundation.

A longer test helps account for these normal changes. Instead of relying on a short snapshot, it gives a more representative average over time.

What Happens If You Test for Too Short of a Time?

If a radon test is too short, the result may give an incomplete picture.

The reading could be higher or lower than the home’s typical average. That can happen because the test only captured one small window of time. This is why a short-term test should not always be treated the same way as a long-term test.

Testing problems can also affect the usefulness of the result. Common issues include:

• Ending the test too early
• Moving the device during the test
• Placing the device in the wrong room
• Opening windows during testing when closed-house conditions are required
• Placing the device too close to drafts, exterior walls, windows, or vents

If you are using a DIY radon test kit, Health Canada recommends following the instructions that come with the radon detector and placing the detector in an appropriate location.

Should You Choose Short-Term or Long-Term Testing?

Choose short-term testing if you need faster information or quick screening.

Choose long-term testing if you want the best picture of your home’s average radon exposure.

For most homeowners who are not under a tight timeline, long-term testing is the stronger choice. It gives a better understanding of the home’s typical radon level over time.

If you want a deeper comparison, read RadonPatrol’s article: Short-Term vs Long-Term Radon Testing: Which One Do You Need?

What Should Homeowners Do Next?

The best next step is to test properly.

If you already have a radon test device, follow the instructions carefully and make sure you understand the required duration, placement, and conditions. If you are unsure, it is worth asking for guidance before starting the test.

RadonPatrol offers professional radon testing in Manitoba and can help homeowners choose the right testing option. We can also help explain placement, timing, and what your results mean.

Frequently Asked Questions

How long should a short-term radon test be?

A short-term radon test should run for at least 48 hours. C-NRPP defines a short-term radon test as lasting at least 48 hours but less than 3 months.

How long should a long-term radon test be?

A long-term radon test should run for at least 91 days, or about 3 months. Health Canada recommends long-term testing for a minimum of 3 months.

Why is 91 days important for radon testing?

Ninety-one days is important because it gives a better picture of average radon levels. Health Canada’s residential measurement guide says Health Canada does not recommend testing for periods shorter than 91 days.

Can I stop my radon test early?

You should not stop a radon test early unless the test instructions or a qualified professional tell you to. Ending the test too soon can make the result less useful.