I am a home buyer in South Florida

Radon Mitigation by Mechanical Ventilation  is a common means of radon reduction and can provide unexpected additional and extremely valuable and desirable benefits to a homeowner and to his family that are much greater than the radon reduction alone.


  1. Buyer selects radon mitigation contractor and technology.
  2. Buyer pays for radon mitigation.
  3. Buyer also pays for post mitigation testing to be performed by the same party that performed the original tests, preferably using the same radon measurement instruments. Seller may offer full or partial credit at closing.
  4. Radon system is installed after closing
  5. Air intake includes a suitable filter device with known and accepted filtration performance and service requirements.
  6. Installation includes a simple means for the occupant to adjust radon levels.
  7. Installation includes proper sealing and drywall restoration of any existing “Radon Fountains.”
  8. System includes a fully functional temperature and humidity controller to operate the radon system automatically.
  9. System includes an electronic radon meter that will provide digital radon measurements and an audible system failure feature.


  • Radon is commonly emitted from uranium U238 contained in the soil and in the hollow blocks used to build exterior walls. A home’s elevated radon results from one or both origins.


  • Ground floor residences that are in contact with the soil commonly experience radon entry through poorly sealed ports or penetrations through the floor slab. An especially troublesome entry  point is where air conditioning Freon lines pass beneath the slab and enter the residence through a hole in the slab. This hole is commonly called a “Radon Fountain.” The Building Code requires that the sealing be performed with expanding urethane foam. TIP: Foam NEVER seals well to block radon entry at that point. Best Practice? Clean thoroughly, remove the black foam sleeve insulating the freon lines, use backer rod to dam the opening and only then apply an elastomeric sealant like self leveling urethane caulk. TIP: Radon mitigators commonly fail to correct this construction defect. TIP: Ensure that all wall openings adjacent to the air handler all (even very small)  are sealed airtight. TIP: Ensure that the condensate drain line has a gooseneck to hold water to prevent air conditioner operation from sucking radon through the condensate drain line.


  • The better built and the more energy efficient the construction, the more likely a  home is to have a radon issue
  • However, design errors and defects in construction are a more likely cause of high radon levels.

I am a home buyer in Central or North Florida

Radon Origin

It appears that in central and in north Florida, most radon is entering the breathing zone from the soil. This is a result of radon-rich rock and soil being closer to the bottom of the floor slab,coupled with sub slab soil being less densely packed than in south Florida. Additionally there is a phenomenon called expansive soils that expand when wet and shrink when dry.  It is  not especially unusual to find that when a slab that had been poured directly on top of the soil the soil may contract as it dries and may pull away from the slab leaving an airspace of 1/2″ to 8″ between the slab and the soil.

I am a condo buyer, high or low rise, anywhere in Florida

Radon Origin and Accumulation

Other than first floor units, the primary radon contributor is the masonry blocks used to construct exterior walls. Masonry blocks typically contain Uranium U238 which goes through radioactive decay and becomes Radon Rn222, a gas. This emitted radon gas collects within the exterior wall cavities between the drywall and the masonry blocks. These exterior wall spaces, or cavities as they are sometimes called, become “radon reservoirs” where radon can build  up to fairly high levels.

Radon Transportation into the Breathing Zone