You cannot see or smell radon, but it can still affect your health and your real estate plans. If you live in St. Clair County, testing is simple, affordable, and the best way to protect your household. In this guide, you’ll learn how radon shows up in our area, how to test and interpret results, what fixes actually work, and how buyers and sellers can handle radon during a transaction. Let’s dive in.
Why radon matters here
Radon is a colorless, odorless radioactive gas that forms naturally in soil and rock. It can enter through cracks, gaps, and utility penetrations and build up indoors. The health risk is real. Radon is the leading cause of lung cancer among non-smokers and contributes to about 21,000 deaths in the U.S. each year, according to the CDC’s radon guidance.
On federal radon maps, much of Michigan is predicted to have elevated indoor radon potential. Many counties fall into the highest predicted category. That means location alone is not a reliable screen. The practical takeaway: every home in St. Clair County should be tested, regardless of age, foundation type, or neighborhood.
The U.S. Environmental Protection Agency recommends action when indoor radon levels are at or above 4 picocuries per liter (pCi/L). You can review the action-level guidance on the EPA’s radon site. Many professionals also consider mitigation at lower readings, such as 2 to 4 pCi/L, to further reduce risk.
How radon testing works
You have several testing options. Pick the one that fits your timeline and your need for precision.
- Short-term tests: Common for screening and real estate. Charcoal canisters typically run 2 to 7 days. Professional continuous radon monitors usually run 48 to 96 hours.
- Long-term tests: Alpha-track or electret detectors sit for 90 days or more. These capture seasonal changes and give a better estimate of your annual average.
- Professional CRMs: Continuous Radon Monitors provide time-stamped results and are preferred for transactions because they deliver rapid, defensible data.
For any short-term test, follow closed-house conditions: keep windows closed and doors opened only for normal entry and exit. Follow the device instructions for placement and HVAC settings.
Typical costs and timing:
- DIY kits: about $15 to $60 each.
- Professional CRM test: often $100 to $300.
- Long-term tests: 90 days or more, plus lab time. Plan weeks to months for results.
Testing is inexpensive compared to the health risk and the cost of mitigation. If you have never tested, make it part of your routine home maintenance.
Understand your results
Here is a simple way to interpret readings:
- Below 2 pCi/L: Low. No mitigation recommended for radon specifically. Retest if conditions change.
- 2 to 4 pCi/L: Moderate. Consider mitigation, especially for sensitive groups.
- 4 pCi/L or higher: EPA action level. Plan to mitigate as soon as practical.
Because radon varies by season, weather, and how you operate your home, follow-up testing is standard if you get a high reading. That may be a second short-term test or a long-term test to confirm before making major decisions.
Fixes that work in Michigan homes
Most St. Clair County homes can be successfully mitigated. The most common and effective method is active soil depressurization (also called sub-slab depressurization). A vent pipe and fan draw soil gases from beneath the slab or basement floor and exhaust them above the roofline.
Other methods are tailored to your foundation:
- Sump pit connection: Often integrated with ASD systems in homes with sump basins.
- Crawlspace encapsulation and ventilation: Seals soil and manages pressure and airflow.
- Sealing cracks: Helpful as part of a comprehensive system, but not effective on its own.
- Mechanical ventilation or HRVs: Useful in certain cases, but may increase energy use.
What to expect on cost and timing:
- Install time: many single-family systems are installed in 1 day of work. Scheduling, permits, and post-mitigation testing can extend the calendar to 1 to 4 weeks or more.
- Costs: nationally, many projects fall in the low thousands of dollars. Pricing depends on foundation, system complexity, and any electrical or roof work needed.
- Verification: always do a post-mitigation test to confirm the system brought levels below the action level. Many mitigators aim for under 2 pCi/L when practical.
For general mitigation guidance and the EPA action level, visit the EPA’s radon page.
Choose a qualified contractor
Hire a radon professional certified by a recognized program. Look for credentials from the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). Ask whether their work follows standards supported by the American Association of Radon Scientists and Technologists.
Questions to ask before hiring:
- Are you certified by NRPP or NRSB? Can you share your credentials?
- Will you perform diagnostic testing and provide a written system design and estimate?
- What approach do you recommend for my foundation type? Can you show photos of similar jobs?
- What permits are required locally, and do you handle them?
- What is the full project timeline and price, including potential extras?
- What warranties cover the fan and workmanship?
- Will you complete post-mitigation testing and provide a written report?
Buying or selling with radon
Radon often comes up during inspections. You can handle it smoothly with clear steps and expectations.
For buyers:
- Include a radon test in the inspection contingency. Ask for a professional CRM test for clear, rapid results.
- If results are elevated, request mitigation or a credit. Require post-mitigation verification.
For sellers:
- Consider testing before you list to reduce surprises. If levels are high, complete mitigation and keep the post-mitigation report handy for buyers.
- Talk with your agent about how to disclose known conditions. Many transactions use addenda that spell out testing timelines and outcomes.
Common negotiation paths when levels are high:
- Seller completes mitigation before closing.
- Buyer accepts a seller credit and completes mitigation after closing.
- Price adjustment with a specified plan for verification.
Because many Michigan areas show elevated potential on federal and state maps, buyers and sellers benefit from planning for radon testing upfront. For map context, review the EPA’s map of radon zones.
Local resources
These trusted sources offer education, maps, and help locating tests and certified pros:
- U.S. EPA radon hub: Testing guidance, action levels, and mitigation basics.
- CDC radon: Health information and homeowner guidance.
- Michigan radon program: State-specific contacts and outreach, including any test-kit programs.
- National Radon Program Services: Education and testing resources supported by Kansas State University.
- AARST: Industry standards and resources.
- NRPP and NRSB: Find certified testers and mitigators.
You can also contact the St. Clair County Health Department for any local test-kit offerings or referrals.
A quick action plan
- Test your home now if you have not already. Use a short-term kit or schedule a professional CRM test.
- If results are 4 pCi/L or above, plan mitigation and confirm with a follow-up test.
- If you are preparing to list, test pre-listing. Keep your results and any mitigation documents ready for buyers.
- If you are buying, include a radon testing contingency and clarify who handles mitigation and verification.
When you want local, transaction-ready guidance, reach out. If you are buying or selling in the Blue Water Area, I can help you plan testing, connect with certified pros, and navigate negotiations with confidence. Visit PortHuronHomes.com to request a free Port Huron home valuation or call Jeff for a personal consultation.
FAQs
What is radon and why is it a concern in St. Clair County?
- Radon is a naturally occurring radioactive gas that can enter homes from the soil; much of Michigan has elevated potential on federal maps, so testing every home in St. Clair County is recommended.
What radon level requires action under EPA guidance?
- The EPA recommends mitigation at 4 pCi/L or higher; many people choose to mitigate at 2 to 4 pCi/L to further reduce risk.
How long does radon testing take for a home purchase?
- Most real estate tests use a professional CRM for 48 to 96 hours, providing fast, defensible results for your inspection contingency.
What does radon mitigation typically involve and cost?
- The most common fix is active soil depressurization; many installs take one workday, with total costs often in the low thousands of dollars depending on the home and scope.
Should the buyer or seller pay for mitigation if levels are high?
- It is negotiable; common solutions include seller-paid mitigation before closing or a seller credit so the buyer completes mitigation after closing, with post-mitigation verification.
