A burst disk on the certified CO2 bottles are rated at least 135 bar, or in most cases 195 bar, because most bottles are rated at 200 bar work pressure.

For a burst disk to fail, as Kane writes, something has to be done very wrong. Overfilling and/or heating the bottle as main reasons. It has been known to happen, even in the pits. But except the noise and a large cloud of white smoke nothing else happened. The worst case I can imagine (oeps, had that happen, but not trough a failed burst disk, but by an used,but not empty extinguisher that started to roll in the trunk), is that a burst disk fails in a bloody hot car, and filling that car with chilly white smoke, making it impossible to see the road and other trafic participants.

The agressive enviroment of the Robot Arena's ain't the issue. If a bottle gets damaged in the fight, it should be discarded and replaced after that fight. If the valve is damaged, you cannot replace it at the venue, unless you have a full rig to test and recertify that bottle.