DanG wrote:
I would guess, if it is a push button, it shuts down all gas usage
in the room. These are typically required in commercial code
settings. It is a bit unusual for the heater and hot water tank,
as I would think they are a bit unusual in a typical setting. The
buttons are seen most often in kitchens, school science labs, etc.

It's not a push button; it's a toggle switch. It looks like just another
typical wall switch except for the red plate and the words on the latter.