@kiwi: don't plumbers do gas work in NZ? If they do the risk to blow up os just the same as with electricians!
Even though late 19th century Vienna houses tend to survive gas explosions they usually don't look pretty afterwards - most of the non-load bearing interior brick walls near the explosion collapse, sometimes the ceilings collapse on several floors... I'd hate to be in there!
One thing to mention though before the gas paranoia gets on again... of the two major gas explosions that happened in vienna during the last few years one was caused by an idiot who tried to DIY disconnect his gas stove (pipe wrench was found in the ruins), while the other one was caused by an equally stupid person messing around with a propane bottle in his kitchen (even though they were able to question him afterwards it never came out what exactly happened). So the conclusion is: as long as you don't mess around with it, gas won't explode.
Oh yeah, the most terrible explosion about 5 years ago (took down an entire 1960s apartment block) was caused by two EXTREMELY ignorant plumbers.
