The following is the legend text from the original DCA published versions of the map:
Radon is a colorless, odorless, radioactive gas generated by the decay of uranium through its radium decay product. Radon from naturally-occurring uranium in soils can enter buildings through pores and cracks in their foundations. Depending on the rates of radon entry and building ventilation, radon can accumulate indoors to levels that increase the risk of lung cancer. Both passive and active features can be built into homes to resist radon entry. However, these features add an incremental cost for new homes and usually a greater cost if installed later. Therefore it is helpful to know if homes in a given region are likely to need radon-resistant features. The Florida residential radon standard seeks to keep radon as low as reasonably achievable, not to exceed 4 pCi/L. This map shows which regions need different degrees of supplementary radon protection to protect public health and satisfy the standard.
The Florida radon protection map was developed from calculated soil radon potentials of nearly four thousand different regions of Florida to identify where passive and active radon protection may be needed and where present construction practices are adequate. To keep radon levels as low as reasonably achievable, passive radon controls are required in each map region where more than 5% of the area is predicted to have radon levels above 4 pCi/L. In regions where the passive radon controls would still allow more than 5% of the area to exceed 4 pCi/L, the passive controls must be supplemented by active radon controls. The indoor radon levels in each different region were computed from simulated rates of radon entry into a reference house from the different soils comprising the region. Radon levels in the reference house were shown to correspond to measured levels in detached houses on a state-wide average basis.
This map should NOT be used to estimate or predict radon concentrations in existing buildings or determine the need to test existing buildings.
Return to the Radon Home Page