Are basically not allowed for gas use with the one exception that I am aware of, basically because they can leak at the packing gland stem.
Did you know they can only leak at the stem when in the open position such as the shut off valve I have pictured in the floor for a fireplace gas ignitor. I shot a little dawn dishsoap onto the valve stem a wala it bubbles.
I don’t use the Hi tech gas meter detectors IMHO they are unrealiable especially outdoors. Soap is reliable under all conditions indoor, outdoor upside down and down side up:D
Its the little things and paying attention to details that keeps your phone ringing