Radon Testing in Selma

Selma sits in the heart of the San Joaquin Valley, where the same flat, clay-heavy soils that make this stretch of Fresno County so productive for agriculture also create conditions worth understanding for radon. Soil composition and the way gases migrate through compacted valley floor geology can influence how radon accumulates beneath slab foundations, and in a city where a significant portion of the housing stock was built during the postwar agricultural boom, with crawl spaces and older concrete work that has had decades to develop cracks and gaps, a radon test for your home is a straightforward precaution that takes the guesswork out of what you’re breathing.

Why Selma Properties Are Worth Testing

Radon is a naturally occurring radioactive gas that forms as uranium in soil and rock breaks down. It has no smell, no color, and no taste, the only way to know it’s present at elevated levels is to measure it. In the San Joaquin Valley, the geology isn’t uniform. Clay-dominant soils can trap and channel soil gases differently than sandy or loamy profiles, and the way a specific parcel drains, or doesn’t, affects how gases move toward a structure’s foundation. Selma’s older neighborhoods, many developed in the 1950s through 1970s, often feature slab-on-grade construction or shallow crawl spaces with limited vapor barriers, both of which are common entry points for radon infiltration. Newer construction in the area has generally improved on sub-slab ventilation, but age alone doesn’t tell the whole story, a well-sealed newer home can accumulate radon just as readily as an older one if the pressure dynamics are right.

Our Radon Testing Process in Selma

Arch Environmental Group uses continuous radon monitoring equipment rather than passive charcoal canisters alone. A continuous monitor logs radon concentrations at regular intervals over the test period, giving a detailed picture of how levels fluctuate, important because radon concentrations can shift with changes in barometric pressure, HVAC operation, and seasonal weather patterns. In Selma’s climate, where summer heat drives residents to seal homes tightly with air conditioning running for months at a stretch, indoor air exchange rates drop and radon can concentrate more readily than it would in a naturally ventilated structure.

The standard short-term test runs 48 hours under closed-house conditions. We place the monitor in the lowest livable area of the home, a finished basement if one exists, or the ground floor if the home is slab-on-grade, and retrieve it at the end of the measurement window. Results are reviewed against the EPA action level of 4 picocuries per liter. If levels come back elevated, we walk through the findings with you clearly before any next steps are discussed.

Arch Environmental Group’s team holds certification as a Certified Asbestos Consultant and Lead Inspector Assessor, with NIOSH 582 microscopist credentials, a background in environmental health science that informs how we approach indoor air quality testing broadly, including radon inspection.

Reaching Selma from Kingsburg

Arch Environmental Group is based in Kingsburg, directly south of Selma on Highway 99. The drive up 99 to Selma is typically under 15 minutes under normal traffic conditions, which means scheduling is straightforward for properties throughout the city. If you’re coordinating a radon test around a real estate transaction with a tight inspection window, proximity matters, we’re not driving in from Fresno or Visalia.

Local Note: Valley Floor Pressure Dynamics in Summer

One pattern worth knowing in Selma and the surrounding valley floor: during the hottest stretches of summer, homes that run central air conditioning continuously can develop what’s called a negative pressure differential, the HVAC system exhausts more air than it draws back in, and the house effectively pulls in replacement air from wherever it can find it, including soil gases through foundation penetrations. This is the same season when windows stay shut and natural ventilation is at its lowest. If your home tests higher in summer than a neighbor’s tested in spring, the difference may be less about your soil and more about how your house breathes. Continuous radon monitoring captures this variation in a way a single passive test cannot.

Scheduling Your Radon Test in Selma

Whether you’re buying a home in Selma, have lived there for years and never tested, or are a landlord with rental units you want to evaluate, radon testing is a defined process with a clear result at the end. Call Arch Environmental Group at (559) 296-2088 to discuss your property, confirm scheduling, and ask any questions about what the test involves. We serve Selma and the surrounding Fresno County communities from our Kingsburg office, and we’re straightforward about what the numbers mean when results come back.