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The Effect of Weather on Radon Testing

Weather can often affect radon levels in a building, so we recommend avoiding testing during unusual weather whenever possible. This includes heavy winds, storms, heavy rain or snow, or unusually warm/cool weather.

Weather events such as the above can temporarily change the radon level in a structure. Typically, these events will increase the radon level in the building, however, not all buildings respond the same – some buildings will see their radon level decrease during unusual weather. 

If unusual weather occurs after you have started your test, don’t worry – your test is not ruined. You will want to take the following steps:

  • Continue to observe Closed House Conditions.
  • Continue running your test.
  • Extend the test duration by at least 48 hours if possible. Do not run the test longer than 7 days (168 hours or it will be invalid). 
  • Send the test back to the lab for analysis, even if you can’t extend the test duration. Your test is not invalid due to the weather. You will want to take the weather into consideration when examining the test results.
  • Below are some examples:
    • Today is Monday at 10am. You started your test yesterday (Sunday) at 10 am – 24 hours ago. Heavy winds start blowing right now. You had planned to stop your test Tuesday at 10am for a 2 day (48-hour exposure). Due to the winds, you decide to run your test longer. You keep running the test and wait until Tuesday at 8am when the heavy winds stop. You decide to run your test for 2 more days (48 hours) and will stop the test Friday at 8am.
    • Today is Monday at 10am. You started your test Friday at 10am – 72 hours ago. It starts raining from a big storm. You keep running the test and wait until Wednesday at 10am when the storm stops. You extend the testing duration to Friday at 10am, 2 full days (48 hours) after the storm stops, and 7 days (168 hours) after the test started.
    • Today is Monday at 10am. You started your test last Wednesday at 10am – 120 hours ago. It starts raining heavily. You keep running the test and wait until Wednesday at 10am, but it’s still raining. Because the test can’t run any longer than 7 days (168 hours), you stop the test at 10am on Wednesday and send it back to the lab.

By running your test for at least 48 hours after the weather event, you are minimizing the effect the weather has on your test results. So, whenever possible, it’s best to extend the testing duration. If the testing duration cannot be extended, your test should still be sent back to the lab. You may need to retest depending on the test results. You can contact our customer service team for advice on how to interpret a test result when weather conditions occur. 

Below are some more details on how and why weather can affect radon levels in buildings:

Changes in weather – particularly extreme weather events – can change the pressure differences and therefore change how radon enters your home. Some weather events, like storms, typically cause radon levels in a home to rise. Other events, like heavy winds, can cause radon levels to either rise or fall. Essentially, weather events can cause your radon levels to either rise or fall. All kinds of weather can affect your test – and there’s no easy way to know exactly which way your test was affected. Typically, light weather events – like a light rainfall, low winds, mild snowfall, etc., do not dramatically affect radon levels. But heavy weather events – severe storms, high winds, etc., often do affect radon levels tremendously.

Here’s a list of some types of weather that affect reading:

  1. Rain/storms – Storms systems bring in lower pressure air around your home. This lower pressure causes radon to “flow” from the soil to the air even faster than normal. If there is heavy rainfall and the ground becomes saturated with water, this makes it harder for radon to find a path through the soil outside the home. This increase in pressure below the surface can increase the radon entering your home – your home has now become the easiest path for radon to reach the air! Radon’s normal “escape routes” can become blocked creating heavier pressure on the soil and pushing the radon gas into lower pressure areas like your home, school, or business. Conversely, rainfall could open some new “routes” for the radon to move easier through, decreasing your levels.
  2. High winds – Wind also influences the air pressure. High winds can either be pushing out the radon (creating high pressure in the home) or “vacuuming” it in (creating low pressure in the home). In most cases, high winds increase radon levels in homes.
  3. Cold winter weather – snow, ice, colder temperatures, etc. Each of these types of weather causes the ground to be more compact and creating pressure for radon to escape elsewhere. In addition to that, colder weather usually means that your home’s heat gets turned up. Heaters can also pull more radon through the building and cause levels to rise. Hot air rises, and if that air is rising and escaping your home, new air must enter your home to fill up that empty space. Some of that air will come from the soil and this can introduce radon into the home. Winter usually yields the highest levels of radon.