system
Given the following post, respond as if you're commenting on Reddit:
human
Why doesn't a lighter explode from the flame spreading back into itself?

I feel stupid asking, but I don't understand how a lighter keeps the fire from spreading back into the tank.  Does the outward pressure overcome the speed of ignition?  Would a less full tank therefore be more likely to explode?
gpt
Your typical butane lighter is filled with a pressurized gas/liquid combination.  When you hit the switch, the pressurized butane flows out of the lighter, combines with air, and then is ignited.  Since the pressure inside is greater than the pressure outside, no oxygen travels into the lighter, and the flame can't propagate into the lighter.