system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How did Luke know removing Vader's helmet would kill him?

In Return of The Jedi, after defeating the Emperor, Vader asks Luke for help in removing his mask, to which Luke responds "But you'll die." How does he know this? I'd imagine the details on Darth Vader's suit aren't common knowledge, even for a hero of the Rebellion. Or is the fact that Vader's suit is mobile life support known?
gpt
If you saw someone run around in a hermetically sealed suit all day you would be worried too if they suddenly wanted you to take it off.

Especially since Luke can feel through the Force that Vader is dying.