There's currently an ongoing discussion (not decision!) in Germany if households could be cut off from gas supply come winter, to make more natural gas available for industry. Of course media is full of millionaires suggesting to wear an extra pullover (no one talks about showers) and incredible banal ideas. One consideration is that gas flow switches are mandated in every house or even at every gas counter. If pressure on the supply side falls, these presumably close and can't be opened by lay persons.
1 & 4: Gas flow switch 2: Main shutoff valve 3: Pressure regulator 5: Gas counter
The gas flow switch works like this and closes if flow velocity is too high, or pressure on the (in this picture left side) is too low:
Other products (also with the DVGW certification, but local suppliers may mandate different types) don't close when the pressure on the supply side is too low:
There's lots of reports that if the gas supply to a street or building is shut off, these will close and then someone qualified will have to open them. I assume the people saying this know their business and are basically correct, but I don't understand the problem yet.
If the gas flow switch works like in the picture above, even it closes when the pressure on the supply side is too low, it should open again when the pressure normalizes - so why is this such an issue?
Gas failure devices also exist, these would also close if the pressure on the supply side falls:
As far as I can tell - I don't have access to the TRGI rules, also different gas suppliers can mandate higher standards - these are not universally installed. I also don't see why these won't open automatically if the pressure on the supply side is reestablished.