Sulphur hexafluoride(SF_6)is widely used as main medium for arc quenching and insulation gas in AIS and GIS high voltage products.However,it is also a gas with a high global warming potential(GWP = 23 900),therefore,searching for alternative gases has been ongoing since the past several decades.In recent years,perfluoronitrile(e.g.C_4F_7N called as C_4-PFN)and perfluoroketone(e.g.C_5F_(10)O called as C_5-PFK)have been proposed as alternative to SF_6.On the other hand AIS and GIS high voltage products based on vacuum interrupting and clean air technology are successfully introduced into operation.In the present article the technical status of SF_6 alternative approaches is summarized and an SF_6-and F-gas free GIS based on clean air insulation and vacuum switching technology is presented.Several key technical considerations,tests and applications with regard to this GIS are given.Firstly,criteria for reliable and safe insulating dimensions of this new GIS are gained through dielectric breakdown tests under various conditions and typical partial discharge tests using clean air as the medium.And vacuum interrupting unit is accordingly improved in certain aspects to meet requirements for high-voltage circuit-breakers.Then the lowcurrent switching tests are carried out on real GIS disconnector and earthing switch,respectively using clear air,C_4PFN mixtures,C_5-PFK mixtures and SF_6 as medium,to determine the switching performance in clean air in comparison with other above gases,and the benefits and drawbacks within clean air are described as well.Moreover,the crucial technical improvements of VIU for HV circuit breaker application are introduced.Finally GIS with these gases are also compared from perspective of safety,environment,operation and maintenance.In conclusion,combining with experiences of real applications of such switchgear,we do believe that this SF_6-/F-gas free GIS,based on clean air insulation and vacuum switching technology,is the ideal replacement of SF_6 GIS.