system
Given the following post, respond as if you're commenting on Reddit:
human
Why does Fire Bending push people back and never seem to burn anyone while fighting?

In Avatar: The Last Airbender, fire bending just seems to knock people back. In most cases, people hit with fire when they are not blocking don't even get burned. What's up?
gpt
It has to do with simple themodynamics: heated gas expands.

Firebending doesn't create any air, it just heats and moves the air near the user (water and other substances can also be heated with firebending, but they can't be moved at all). This rapidly heating air expands quickly, creating the concussive effect. In fact, most of the older firebending forms are based around knocking down your opponent and using shock and awe to make an opponent flee or surrender (the older lightning bending forms and the newer firebending forms developed by the Fire Nation military are more lethal but hard to practice on dummies). Statistically, the majority of firebending injuries are broken ribs from being knocked around and burns from clothing catching fire.

Normally if you're outside this will just knock back your target, but if firebender bends in an enclosed space there can be an explosion. If a firebender used a technique in a sealed container the container would rupture (or become very hot and pressurized). This isn't very useful for containing firebenders, though, because an airtight container would eventually suffocate a normal person. That's why firebenders have to be imprisoned in a chilled environment (which works for unrelated reasons based on the firebender's breath and chi).