BattleMonkey said:Airtight seals? Hardly when the back the predators heads stick out on most of their helmets and many just slip off. Unhooking tubes that shoot out some gas does not mean airtight. Predators in all the movies are shown without their helmets without issue.
I think there's a good amount of evidence that the helmets ARE airtight. Just because their backs are exposed doesn't really mean much, since the helmet covering the face is probably attached to their facial/bone structure such that it remains airtight while exposing the hair for cultural reasons.