So I wake up one day and the boiler won't work. No warm water. I trace the problem to the boiler not having sufficient pressure - it just needs to have water refilled. Problem is that I don't know where to top it up. The landlord doesn't know and tells me to call a technician. I call Vaillant (the boiler maker) and get a technician to come around fix the problem. Apparently they don't let normal people fill their boilers since there has been a string of accidents. (Strangely, Brits can be trusted to do this but not Austrians.)
Two days of cold showers later the technician comes along, refills the boiler and turns the gas off due to a gas leak.
Which means some more cold showers, but also the odd opportunity of getting a picture of what a boiler with a warning tag looks like.