Has anyone looked into what might be leaching into the cockpit itself during flight? With all that equipment, seems there'd be a lot of exotic material getting heated up, possibly getting vaporized into the air outside the mask. If a guy goes to scratch his nose or something, he might inhale something he shouldn't, something that might interact with the stresses of high g-load or something else. How is cockpit temperature maintained anyways? It might explain why the problem seems worse in Alaska. Perhaps a heating element of some kind is having to burn hotter or longer than usual in the colder climate. Has anyone ever noticed how heaters sometimes give off fumes when they're turned up all the way?
I'd personally look into what would be producing natural gas in flight. That just sounds too odd.