Understanding Radon Risks in Temecula Homes: What Every Buyer and Seller Should Know

When the Martinez family bought a brand‑new ranch‑style home in a Temecula subdivision, the real‑estate agent highlighted the modern HVAC system and low‑maintenance landscaping. A month later, a simple home‑energy audit revealed a radon level of 5.2 pCi/L – well above the EPA’s action level. The discovery sparked a flurry of questions: Is this common in our area?Do we need expensive mitigation?Can a home inspection catch it before we move in?

Orlando Martinez, lead inspector at Marine One Property Inspections, has seen similar cases across the Inland Empire, from Riverside basements to San Diego condos. This post walks you through why radon matters in Southern California, how a proper inspection works, and what steps you can take if the numbers are high.

Why Radon Shows Up in Temecula and the Inland Empire

Radon is a naturally occurring radioactive gas that forms when uranium in soil and rock decays. The gas moves upward through cracks, pipe penetrations, and foundation gaps, eventually pooling in enclosed spaces.

• Local geology matters – The Temecula Valley sits on granitic and volcanic soils that can release more radon than the sandy soils of coastal San Diego.
• Construction style – Many homes in the Inland Empire are built on concrete slabs or have crawl‑spaces, both of which can trap radon beneath the floor.
• Seasonal patterns – Summer heat and low humidity in Temecula can increase the stack effect, pulling radon from the ground into living areas, while cooler Winters may temporarily lower indoor levels.

Because radon is odorless, colorless, and tasteless, homeowners often remain unaware until a test is performed. Long‑term exposure at elevated levels has been linked to lung cancer, making early detection a public‑health priority even in areas that don’t traditionally rank as “high‑radon.”

How Marine One Performs a Radon Test

Marine One Property Inspections offers two complementary services:

1. Short‑Term (48‑hour) Test – Ideal for sellers who need a quick snapshot before listing. The device is placed in the lowest lived‑in level and left undisturbed while the home’s HVAC system runs normally.
2. Long‑Term (30‑day) Monitoring – Recommended for buyers and anyone concerned about seasonal fluctuations. The monitor records hourly readings, giving a more accurate average.

Our process follows best‑practice guidelines:

• A calibrated radon detector is positioned at least 3 ft from walls and 2 ft above the floor, away from drafts and direct sunlight.
• The device stays in place for the chosen testing period, with Orlando or a qualified technician checking placement and logging conditions.
• After retrieval, results are uploaded to a secure portal, and a clear, written report explains the findings and next steps.

Image Description: a compact radon test device sitting on a coffee table in the living room of a two‑story suburban home in Temecula, with a window showing a sunny backyard.

Interpreting the Numbers and Planning Next Steps

The EPA’s recommended action level is 4 pCi/L. If your test reads:

• Below 4 pCi/L – The home is within the guideline range, but you may still consider mitigation if you have vulnerable occupants (children, smokers, or those with respiratory issues).
• 4 pCi/L or higher – A radon mitigation system is advisable. Common solutions include:
• Sub‑slab depressurization – A vent pipe and fan draw radon from beneath the slab and vent it outdoors.
• Sealing foundation cracks – Reduces the pathways radon uses to enter the home.
• Ventilation upgrades – Improving exhaust fans in bathrooms and the kitchen can help dilute indoor radon.

Marine One does not install mitigation systems, but we maintain a vetted network of licensed radon mitigation contractors throughout Riverside, San Bernardino, and Orange County. We can provide you with a detailed mitigation plan and coordinate follow‑up testing to confirm that levels have dropped to a safe range.

Note: Radon testing is a snapshot; repeat testing after any major renovation or HVAC change is prudent.

Special Considerations for Different Property Types

• Multi‑unit buildings – Radon can vary floor‑to‑floor. Our technicians use a CrawlBot foundation inspection to access tight crawl‑spaces in a Riverside duplex, identifying entry points that a visual inspection might miss.
• Commercial properties – Larger square footage and complex HVAC systems require a strategic placement of multiple monitors. Marine One’s commercial inspection certification ensures we meet those demands.
• New construction – Even brand‑new homes can have radon issues if the slab isn’t properly sealed. A pre‑occupancy radon test can save future owners from surprise mitigation costs.
• Pool and Spa homes – The presence of water features can affect indoor humidity and pressure differentials, potentially influencing radon movement. Our radon testing includes monitoring near pool houses and attached garages.

By tailoring the test location and duration to each property’s layout, we give you a realistic picture of radon exposure.

Image Description: a small, wheeled inspection robot (CrawlBot) navigating a dark crawlspace beneath a single‑family home in Riverside, with exposed joists and a concrete slab visible.

Radon is one of the few home‑health hazards you can control with the right information. If you’re buying, selling, or simply maintaining a property in Temecula, Riverside, or any of the surrounding communities, a professional radon test from Marine One Property Inspections gives you peace of mind and a clear path forward.

Orlando Martinez and his team are ready to answer your questions, schedule a test, or discuss mitigation options. Reach out today for a no‑pressure consultation—whether you need a quick short‑term test for a listing or a comprehensive 30‑day monitoring plan for a new purchase, we’re here to help you protect your home and family.