Radon is a colorless, odorless radioactive gas that can accumulate in homes and buildings, posing a serious lung cancer risk. Testing is the only reliable way to know if your home has elevated radon levels.
Radon follows pressure gradients. Because building interiors are typically at slightly lower pressure than the soil beneath — due to stack effect, HVAC operation, or exhaust fans — soil gas gets drawn inward through any available pathway.
Slab-on-grade construction: The dominant home type in South Florida. Radon enters through cracks in the slab, expansion joints, gaps around pipes and conduits, and porous block construction. CBS construction: Hollow concrete block cores can act as conduits for soil gas. Well water: Groundwater can contain dissolved radon that off-gasses indoors when aerated.
Radon testing is the only way to know your exposure level. Tests are inexpensive and available through state-certified laboratories and hardware retailers.
Short-term tests (2–7 days): Passive charcoal canisters placed in the lowest livable level. Best as a screening tool. Long-term tests (90 days to 1 year): Alpha track detectors provide a time-integrated average that better represents actual annual exposure. Interpretation: EPA action level is 4 pCi/L. Between 2–4 pCi/L, EPA recommends considering mitigation. The WHO reference level is 2.7 pCi/L — lower than the EPA threshold.
The most effective mitigation technique for slab-on-grade Florida homes is sub-slab depressurization (SSD). A licensed contractor installs a suction pipe through the slab connected to a continuously running fan that draws soil gas from beneath the slab and exhausts it above the roofline before it can enter the living space.
A well-designed SSD system typically reduces indoor radon levels by 50–99%. Post-mitigation testing should confirm the result. Contractors should be certified by the NRPP (National Radon Proficiency Program) or NRSB (National Radon Safety Board).
Radon-222 decays into radioactive progeny that attach to airborne particles and are inhaled, depositing energy directly in bronchial tissue and causing DNA damage that can initiate lung cancer over years of exposure. The risk is multiplicative with cigarette smoking.
The EPA’s risk chart shows non-smokers at 4 pCi/L face approximately 7 lung cancer deaths per 1,000 people over a lifetime — higher than most regulated environmental contaminants. There is no established safe level; risk increases linearly with dose.
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South Florida Indoor Air is an independent educational resource dedicated to helping our community breathe better and make informed decisions about the air inside their spaces.