Batman has just never forgiven Hal Jordan for the time Hal passed gas inside that ring-generated bubble:
Hal: “It wasn't me, Bats -- it was the Guardian. Honest!”
Bruce: “You've been eating Green Arrow's chili again, haven't you!”
Guardian: “While learning your Earth customs, I have heard that an appropriate response in situations like this is, 'The one who smelled it ...'”
Wow. Doing that in front of Batman, and in an enclosed environment, is proof that Hal has no fear. Not only that, how horrible it must be to be stuck with a static air supply! I hope Hal included an air filtration system on that thing.