Talk:Portal 2 Chapter 4 Test Chamber 21 (Escape)
If you stay for too long in chamber 21 after Wheatley opened the wall for you to escape, GLaDOS fills it with neurotoxin. I found it while playing in "developer commentary" mode - I forgot that those commentaries don't pause the game and stayed in place to listen. When the commentary ended the whole room was green. I quickly ran out and was able to complete the game normally.
- Are you sure it was Neurotoxin? It could have just been a lighting glitch from GlaDOS's trick.