When Is High Radon Considered a Long-Term Problem?

You got your radon test results, and the number came back higher than expected. Now what? Is it an emergency or something to keep an eye on?

Take a breath. Radon is rarely an immediate hazard. The risk builds over time, not overnight. In this guide, we’ll break down what “long-term” radon exposure means, when to take action, and when it’s okay to retest or wait. You’ll also learn how ongoing monitoring plays a key role in protecting your home.

Understanding Radon and Its Long-Term Risk

Radon is a naturally occurring radioactive gas that enters homes from the ground. It’s invisible and odorless, but long-term exposure to high levels increases your risk of developing lung cancer. 

It’s important to remember that this risk comes from ongoing exposure. You won’t notice symptoms right away, and a single high reading doesn’t automatically mean danger.

What Is Considered Long-Term Exposure to Radon?

Long-term exposure means consistently elevated levels over several months or years. Unlike acute threats like gas leaks or carbon monoxide, radon doesn’t cause immediate illness. Its danger lies in the cumulative impact over time. 

Think of radon as a slow and sneaky risk. The longer you’re exposed to levels above the EPA’s action threshold, the greater the risk. Continued monitoring is essential, even if the first result is high.

When Does Radon Need to Be Mitigated?

Radon is measured in picocuries per liter (pCi/L) of air. The Environmental Protection Agency (EPA)’s action level is 4.0 pCi/L. If your home’s radon level is 4.0 or above, it’s considered high and calls for mitigation.  

Remember, there’s technically no “safe” radon level, and any exposure carries some risk. The EPA even suggests considering mitigation for levels between 2.0 and 4.0 pCi/L.

Key point: Radon becomes a long-term concern when levels stay elevated (especially above 4.0) for an extended period. The higher the reading and the longer the duration, the greater the risk.

When It’s Okay to Wait or Retest

Not every high reading means you need immediate mitigation. In some situations, follow-up testing and time can help you make a more informed decision.

Borderline Results (Around 4.0 pCi/L)

Start with a follow-up test if your result is right around the EPA action level. Radon levels can vary from day to day and season to season. Your first test might have caught a particularly high (or low) period. A long-term test or retest gives a better picture of your average exposure.

Mitigation is recommended if:

• Your long-term retest confirms a level over 4.0 pCi/L

• You do two short-term tests, and the average is 4.0 or higher

Seasonal and Environmental Fluctuations

It’s common for radon levels to fluctuate. They can swing due to weather changes, how much you ventilate your home, temperature differences, etc. It’s not unusual to see varying radon levels in your home, especially if there’s a storm or your HVAC usage changes.

Short-term tests might not accurately capture your average radon level. If you got one high reading during a crazy rainstorm, don’t panic. It could be a temporary spike. However, don’t just assume it’s always a fluke. Retest under normal conditions to be sure. 

Also, consider the time of year. Radon tends to be higher in winter when homes are closed up and a bit lower in summer when windows are open. A long-term test will naturally account for these seasonal differences.

Slightly High Reading After Mitigation

Perhaps you mitigated and got an elevated follow-up reading. Before ripping it all out, test again to verify. If your results consistently hang just above 4.0, talk to your mitigator. Minor adjustments might get you below the line. 

Key point: Radon is a long-term issue, so it’s okay to take a few weeks or even months to confirm your average level. Just follow through with retesting, rather than assuming fluctuations mean you’re in the clear. Use additional testing or a long-term radon detector to make an informed decision.

When Do You Need to Act?

Once high radon levels are confirmed, don’t wait too long to get started on mitigation efforts. Here's how to gauge urgency:

Confirmed Readings Above 4.0 pCi/L

If your average level is above the EPA threshold, plan to install a mitigation system in a timely manner. It’s not an emergency, but it’s not something to ignore, either. Think of your timeline in terms of weeks or a few months, not hours or years. The sooner you reduce the levels, the better for your long-term health.

Very High Readings (Above 8.0 pCi/L)

If your first test shows a level well above 8.0,  that’s a huge indication you need to act quickly. The EPA’s guidance is that if your initial short-term test is more than twice the action level (i.e., more than 8 pCi/L), you should immediately conduct a second short-term test to verify it.

Extremely high readings are unlikely to be flukes and suggest a more urgent need for mitigation. “Immediately” doesn’t mean evacuating your house, though. It means scheduling another test within days and contacting a professional soon after if the result is confirmed.

Still High After Mitigation

You paid for a fix, but your follow-up test still reads high. First, double-check that test with another to rule out any errors or unusual conditions. If your level remains above 4.0, contact your radon contractor to adjust or add to the system. A properly installed mitigation system should bring levels below 4.0 pCi/L. Sometimes, improving the seal on cracks, adding another suction point, or increasing fan power may be needed. 

Key point: High radon levels shouldn’t be ignored once confirmed. Whether it’s your first test or a post-mitigation follow-up, a reading above 4.0 pCi/L should lead to next steps, not indefinite waiting.

Long-Term Monitoring: Your Best Defense

Ongoing radon monitoring gives you peace of mind. Whether you use a radon monitor or perform seasonal tests, keeping an eye on trends helps you make smart decisions.

Radon doesn’t always stay the same. It rises and falls with the seasons, ventilation habits, and home changes. Long-term data gives you a more accurate risk picture than any single test.

Confirmed High Levels? Call The Radon Guys

Seeing radon levels above 4.0 pCi/L can be unsettling, but it doesn’t always mean immediate action is necessary. The key is monitoring over time and understanding what your results really mean. If your levels aren’t trending down or you’ve had elevated readings for several months, it may be time to consider next steps. The Radon Guys are here to help you interpret your results, answer your questions, and provide expert mitigation solutions if needed. Reach out today for honest guidance and peace of mind.