Gas blast applied on the arc must be able to cool it rapidly
so that gas temperature between the contacts is reduced from
20,000 K to less than 2000 K in a few hundred microseconds,
so that it is able to withstand the transient recovery
voltage that is applied across the contacts after current
interruption. Sulphur hexafluoride is generally used in
present high-voltage circuit-breakers (of rated voltage
higher than 52 kV).

In the 1980s and 1990s, the pressure necessary to blast the
arc was generated mostly by gas heating using arc energy. It
is now possible to use low energy spring-loaded mechanisms
to drive high-voltage circuit-breakers up to 800 kV

we can use the air circuit breakers for 2amps upto 2,000 
amps.as per the british standard.

As per IS- we can use the ACB for 800 Amp.- 4000 Amp.

For ACB's the upper load current range shall be selected
with some safety margin and some future capacity also to be
considered.