The gas is acidic which will soon break down the seals protecting the isolated rooms.
Jack tries to go to the controls that will allow Chloe to flush the nerve gas from the building but he can't reach it.
Lynn is close enough to reach it but doing so means he and his guard will both die. Lynn makes it to the computer, shuts down a security program and makes it back to his cell only to die a few seconds later along with the guard.
As the gas is pumped out, Tony is about to shoot Henderson but can't do it. So he fills a syringe full of poison instead but suddenly Henderson grabs the syringe, stabs Tony.
Jack runs in shortly afterwords, holds Tony who says "She's gone, Jack" and he dies.