Apparently 30mA for 0.5s can kill you...
Those circuit breaker thingies measure what "goes out" to the consumer and what "comes back" in. If there's some current lost somewhere, it will immediately (about 40ms) break the circuit. Quite guickly actually...
I found a nice
graph, unfortunately it is in German.
The white area on the left means "no danger". The grey area next to it means something like "danger of accidents due to 'jump-reactions'". The stuff on the right stands for "highest mortal danger".
The little dotted line is an "identifiying line" for certain circuit breakers.
As you can see, overall it all looks very nice. You still have a problem when high currents occur for a short period of time though...