云锡公司下属老厂、马拉格、松树脚、黄茅山、卡房等五个矿山,开采历史悠久,旧巷道和采空区分布广,生产中段多、高差大。巷道大部份开掘在游离二氧化硅含量极低的大理岩中,长期靠自然通风。但各矿井下空气中氡浓度和氡子体α潜能(1972～1976年的平均值)分别高出“放射防护规定”最大允许值的0.1～3.1倍和0.22～6.62 There are five mines, such as the old factory of Yunxi Company, Malague, pine foot, Huangmushan and card house. The mining has a long history and the old roadway and goaf are widely distributed. Most of the roadway is excavated in marble with extremely low silica content and naturally ventilated for a long period of time. However, the radon concentration in air and the α potential of radon progeny (average value from 1972 to 1976) in each mine are respectively 0.1- to 3.1-fold and 0.22-6.62 higher than the maximum allowable value of “Radiation Protection Provisions”