On my air tool compressor or scuba gear you can see or hear a diaphragm regulator sloughing off a tiny amount of gas to the atmosphere when you adjust the regulator down. Does a natural gas regulator do the same if there is variation in the supply line pressure?
According to a valued associate from Washington DC Gas, residential regulators can vent small amounts of raw natural gas to the surrounding environment and cannot be enclosed. Any enclosed regulator say, in a ship, must have active ventilation measures. Interior appliances like water heaters are regulated from the external regulator and do not vent.