Radon concentrations in caves, e.g. the Great Cave of Niah, Sarawak in Miocene Subis Limestone, show that archaeological excavators are at risk from exposure to naturally occurring radioactive gas (radon, Rn222), with cave dwellers being exposed to an estimated dose of 26.42 mSv. The IRR (1999) indicates a maximum dose to a member of the public should be no more than 1 mSv annually. In the Creswell Crags Permian limestone caves (UK) radon increases with increasing distance into the caves, due to ventilation and topography, with cave dwellers exposed to a possible dose of 15.86 mSv. The Carboniferous Limestone Clapham Cave (UK) presents similar issues. The risks outside a cave, at the front entranceway and deep inside (those producing rock art may be a kilometre in) is noted, for a variety of cave occupancies and types. Such environments may have been poorly ventilated, and smoky, increasing radon risk