4.0 is formally specified as warning line.
But actually, long exposure to radon level at 2.0 can be problematic too.
顺便提醒大家买房注意查radon, 美国non-smoker 1st reason for lung cancer
myenglishid (2009-07-01 20:48:57) 评论 (1)4.0 is formally specified as warning line.
But actually, long exposure to radon level at 2.0 can be problematic too.