The CB uses SF6 gas instead of Oil or Vacuum as the 
insulation medium

SF6 is Sulpher hexa Flouride gas.. if this gas is used as 
arc quenching medium in a Circuitbreaker means SF6 CB

Sulpher hexa flouride circuit breaker is used instead of
abcb and ocb,s for its more safe opening and lesser duration
of electic arc produced during opening.also lesser
maintainace required for this.it occupies less space also.

Sulphur Hexaflouride is a SF6 CB

my dear frend sajid, sf6 cb needs more attention than abcb 
and vcb because they hardly need any maintenance.