system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what prevents the flame on a gas stove from igniting the gas that’s in the supply line and blowing everything up?
gpt
Fuel + oxygen + heat = fire

The gas line is full of fuel, but no oxygen or heat. So no fire.

As it comes out at the burner, a constant outward flow of gas blocks oxygen from backfilling the gas line. So it should never be a problem as long as it stays under pressure and has no leaks.