查了一下... :-)

来源: 于 2014-11-24 17:03:41 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次
"Radon Act 51 passed by Congress set the natural outdoor level of radon gas (0.4 pCi/L) as the target radon level for indoor radon levels. Unfortunately two-thirds of all homes exceed this level"... :-)