Radon concentration in three Florida caves: Florida, Jennings, and Ocala
This study reports the first radon concentration measurements within three frequently visited caves in Florida: one touristic (Florida Caverns), one private (Ocala Caverns), and one private, but publicly accessible (Jennings Cave). To measure the radon concentration, 18 CR-39 solid-state alpha track detectors were placed along the main passages of these caves for a period of 2 months (between December 2016 and February 2017). The results show that the radon concentration throughout all caves greatly exceeds the recommended safety action level. The highest concentrations of 2737 and 2958 Bq m−3 were recorded in Ocala and Jennings caves, respectively; whereas in Florida Caverns, the concentration reached a value as high as 1050 Bq m−3. To aid in ventilation, allowing the built-up gas to disperse, it is suggested that at Florida Caverns, the entry doors to be periodically opened for several hours. In locations with high concentrations where additional ventilation is not possible, such as Ocala and Jennings, it is recommended that the exposure time to be limited. Although radon values measured in the surveyed caves are high, the occasional cave visits are generally safe as the overall exposure time is minimal. However, cave guides and workers may have an increased risk as they spend many hours a day during which they are exposed to these high radon concentrations.